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Storage Stability: Shelf Life Testing

E. Torrieri, in Encyclopedia of Food and Health, 2016

Gas Atmosphere

The composition of the atmosphere that surrounds the product affects its deteriorative process. When the food product is packed, the gas composition of the package head space is a function of the packaging properties (gas permeability) and product properties (respiration rate or chemical reaction kinetics). Oxygen is an active reactant in many chemical reactions (oxidation, enzymatic browning, and physiological metabolism). Its availability has detrimental effects on the nutritive quality of foods. Thus, in many cases, removing oxygen from the surrounding atmosphere of a product leads to positive effects on the shelf life of the product. Exceptions are all the respiring products, which, after harvest, keep on respiring, consuming oxygen and sugar, and producing carbon dioxide, water, and energy. If the product has less oxygen available for the metabolic process, it reduces the respiration velocity to preserve itself. Low oxygen content also suppresses the production of ethylene, therefore delaying the onset of ripening. Moreover, concentrations of oxygen lower than the threshold value below which anaerobic condition establishes can be even detrimental for the shelf life of the product. At the same time, it is reported that high concentrations of CO2 inhibit the respiration rate, and as for oxygen, high levels of CO2 may affect negatively the quality of the product.

Carbon dioxide and carbon monoxide improve the stability of the foods. In fact, high levels of carbon dioxide lead to a reduction in microbiological activity, especially mold growth, denaturation of some protein by acidification, inhibition of pectin hydrolysis, and a reduction in the cold damage of the vegetable tissue. However, different commodities have different optimum gas composition requirements for maximum shelf life.

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Endogenous formation of trans fatty acids: Health implications and potential dietary intervention

Wei-Lun Hung, ... Chi-Tang Ho, in Journal of Functional Foods, 2016

4 Cis–trans isomerisation of fatty acids by nitric dioxide

Nitrogen dioxide is a nitrogen-centred radical with potent oxidising properties. The adverse effects of nitrogen dioxide have been reported in some detail (Hesterberg et al., 2009). Nitrate has been employed as a food additive to protect cured meat from the decomposition and spoilage by spore-forming bacteria such as Clostridium botulinum (Christiansen, Johnston, Kautter, Howard, & Aunan, 1973). In the mouth, nitrate is reduced to form nitrite by a group of nitrate-reducing facultative anaerobic bacteria. Because of exposure to the acidic environment of the stomach, nitrite is rapidly converted to nitrous acid, which in turn decomposes to nitric oxide and nitrogen dioxide (McKnight, Duncan, Leifert, & Golden, 1999). Nitrogen dioxide can also be endogenously formed in vivo through oxidation of nitric oxide. Nitric oxide is a small gaseous molecule that plays an important role in the regulation of the cardiovascular, immune and nervous systems. Nitrogen dioxide is a gaseous free radical that can react with the double bonds in olefins and fatty acids through several reactions including nitration, peroxidation and isomerisation (Balazy & Poff, 2004; Pryor & Lightsey, 1981; Pryor, Lightsey, & Church, 1982). Similar to thiyl radicals, nitrogen dioxide catalyses the cis_–_trans isomerisation of unsaturated fatty acids via a reversible addition–elimination reaction (Fig. 3). The cis_–_trans isomerisation is initiated by the addition of nitrogen dioxide to the double bond to form a highly reactive carbon-centred radical. The rearrangement of this intermediate radical followed by elimination of nitrogen dioxide leads to the formation of a thermodynamically favourable double bond with trans configuration. In MUFA, Litchfield, Harlow, Isbell, and Reiser (1964) found that nitrous acid catalyses cis_–_trans isomerisation of oleic acid (Litchfield et al., 1964). In their study, nitric acid reacted with sodium nitrite to form nitrous acid, which further dehydrated to form dinitrogen trioxide (N2O3) in the presence of nitric acid. The decomposition of N2O3 produced nitrogen dioxide, which was responsible for the isomerisation reaction of oleic acid. Nitrogen dioxide catalysed cis_–_trans isomerisation with arachidonic acid (Jiang et al., 1999). An arachidonic acid-added _n_-hexane solution bubbled with gaseous nitrogen dioxide results in the formation of trans isomers of arachidonic acid. All four mono-trans isomers of arachidonic acid have been identified where their double bond position was not shifted. Interestingly, mono-trans isomers of arachidonic acid were also found in human platelets after exposure to nitrogen dioxide. However, several reviews have summarised that nitrogen dioxide-mediated cis_–_trans isomerisation was not promising when considering the reactivity of nitrogen dioxide to other components within tissues (Chatgilialoglu & Ferreri, 2005; Chatgilialoglu, Ferreri, Lykakis, & Wardman, 2006; Chatgilialoglu et al., 2014). The kinetic data suggested that nitrogen dioxide had high reactivity towards uric acid, glutathione and cysteine (Ford, Hughes, & Wardman, 2002). Furthermore, nitrogen dioxide is also highly reactive towards antioxidants, such as ascorbic acid (Alfassi, Huie, Neta, & Shoute, 1990). Thus, it is predicted that nitrogen dioxide generated in vivo will be rapidly reduced by thiols, and subsequently results in thiyl radicals that induce the cis_–_trans isomerisation.

Fig. 3. Nitrogen dioxide-catalysed cis_–_trans isomerisation of unsaturated fatty acids.

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Engineered bacteria for valorizing lignocellulosic biomass into bioethanol

Hamed Kazemi Shariat Panahi, ... Meisam Tabatabaei, in Bioresource Technology, 2022

1 Introduction

About one-fifth of the world’s annual energy is consumed by vehicles, with gasoline and diesel engines as the most-used internal, intermittent combustion engines (Dehhaghi et al., 2021; Tabatabaei et al., 2019). The main transportation fuel in many cities worldwide is gasoline because it is cheaper, more responsive, or operational at higher engine speeds (Dehhaghi et al., 2021). Together with the growing middle-class populations in the developing world, these advantages are expected to increase the global gasoline demand by 43–47 million tons by 2025 (Dehhaghi et al., 2021).

The inevitable exposure of city residents to gasoline exhaust gas emissions, i.e., ozone, sulfur dioxide, lead, particulate matter, NOx, CO, and unreacted hydrocarbons, has adverse health effects (Dehhaghi et al., 2021; Panahi et al., 2021). Another challenging issue is the generation of greenhouse gases which subsequently cause climate change (Panahi et al., 2020b; Tabatabaei et al., 2020b). These challenges can be mitigated by phasing out gasoline consumption (Panahi et al., 2019c). Currently, bioethanol and electricity are the two most promising alternatives for gasoline. The high price and low efficiency of electric vehicles and lack of infrastructure limit the application of electricity as a transportation fuel. In contrast, the liquid nature of bioethanol (simple and cost-effective storage) and its compatibility with the existing gasoline engines and infrastructures make it a superior gasoline substituent over electricity (Panahi et al., 2020a; Dehhaghi et al., 2020). For example, flexible fuel vehicles with port fuel injection engines and spark ignition systems can run on gasoline-ethanol blends with ethanol contents of up to 85% (E85) (Panahi et al., 2019a). However, to avoid food vs. fuel debate, the first-generation feedstocks (e.g., sugary and starchy feedstocks) must be replaced with the second-generation (e.g., lignocelluloses), the third-generation (e.g., microalgae, macroalgae), or the fourth-generation feedstocks (genetically modified organisms, GMOs) (Aghbashlo et al., 2018; Alidadi et al., 2020; Mirmohamadsadeghi et al., 2021; Tabatabaei et al., 2020a). The current cultivation of macroalgae/microalgae is not economically feasible (Panahi et al., 2020), whereas GMOs cultivation may raise environmental concerns (Dehhaghi et al., 2021). Despite the high availability of second-generation feedstocks, lignocellulosic bioethanol price is high due to biomass conversion difficulty (Amid et al., 2021; Soltanian et al., 2020). As a result, bioethanol is only applied as a gasoline extender (octane booster and gasohol) at low ratios, commonly at 5–10% (Panahi et al., 2020).

One of the major constraints of developing an economically feasible lignocellulosic bioethanol industry is the lack of suitable ethanologenic microorganisms (Naghshbandi et al., 2019). Following delignification and saccharification, lignocellulose breaks into hydrolysates containing carbohydrates (e.g., xylose) that may not be fermentable by Saccharomyces cerevisiae. This shortcoming can be addressed by engineering microorganisms to selectively produce ethanol at high productivity (>1 g/L/h), concentration (>40 g/L), and theoretical yield (>90%). Besides the ability to grow in lignocellulosic hydrolysate, the engineered microorganism must possess other important characteristics, for example, high ethanol tolerance, high ethanol productivity and selectivity, and ability to grow in harsh conditions (low pH and high temperature). Alternatively, cellulolytic microorganisms can be engineered for producing ethanol through consolidated bioprocessing. Table 1 presents some engineered bacteria with annotated target genes, the assimilated substrates, and the ethanol titers.

Table 1. Some engineered bacteria with annotated target genes, their assimilated substrates, and their ethanol titers.

This review scrutinizes the current understanding of the engineered bacteria, focusing primarily on those strains that may have valuable trait/s for lignocellulosic ethanol production. The constraints and solutions for developing such engineered microorganisms concerning ethanol yield, titer, and production rate are also discussed. The current review is among a few reports specifically and critically dealing with engineering Escherichia coli, cyanobacteria, Zymomonas mobilis, and eight thermophilic bacteria (viz., Thermoanaerobacterium saccharolyticum, Thermoanaerobacterium aotearoense, Clostridium thermocellum, Thermoanaerobacter mathranii, Thermoanaerobacter ethanolicus, Caldicellulosiruptor bescii, Geobacillus thermoglucosidasius, and Moorella thermoacetica) for lignocellulosic bioethanol production. The novelty of the present review against the previously published ones has been clarified in Table 2.

Table 2. Comparison of the present review article and previous articles published on engineered bacteria for lignocellulosic bioethanol production.

*Where available.

**Eight bacterial species.

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STUNNING | CO2 and Other Gases

A.B.M. Raj, in Encyclopedia of Meat Sciences, 2004

Mechanisms of Induction of Unconsciousness

Carbon dioxide induces unconsciousness through inhibition of neurons. This mechanism is closely related to the fall in pH of the cerebrospinal fluid (CSF), which bathes the brain and spinal cord. It has been reported that unconsciousness begins when the CSF pH falls below 7.1 and reaches a maximum at pH 6.8. More recent research carried out in New Zealand, involving laboratory rats, suggests that inhalation of carbon dioxide leads to excessive release in the brain of γ-aminobutyric acid (GABA), which is the major inhibitory amino acid neurotransmitter. However, since the GABA level has been known to increase during distress and anxiety, it is not certain whether the increase in GABA level is due to the stress of induction of unconsciousness with this gas or a physiological mechanism involved in carbon dioxide-induced neuronal inhibition.

Inhalation of carbon dioxide does not lead to a reduction in the blood oxygen level and, therefore, anoxia does not accompany the inhalation of carbon dioxide at concentrations required for stunning animals. In addition, the anaesthetic effect of carbon dioxide is independent of residual oxygen in the breathing mixture. For example, a mixture of 40% carbon dioxide and 30% oxygen will also render animals unconscious. The time to onset of unconsciousness in pigs is related to concentrations of carbon dioxide between 40% and 70% by volume in air. Increasing the concentration of carbon dioxide in an air mixture above 70% by volume does not reduce the time to loss of consciousness greatly. However, the times to loss of consciousness in terrestrial poultry species seem to be very similar during exposure to 40% by volume or more of carbon dioxide in air and are rather prolonged when 20% by volume or more of oxygen is added to the mixture. The time to onset of death in both species is related to the concentration of carbon dioxide and the duration of exposure to the gas. Gas mixtures containing carbon dioxide and 30% by volume or more of oxygen do not induce death and therefore require a killing procedure (e.g. further exposure to a high concentration of carbon dioxide in air).

In general, anoxia occurring as a result of the inhalation of argon and/or nitrogen induces unconsciousness by depriving the brain of oxygen. For example, it has been established that cerebral dysfunction occurs in mammals when the partial pressure of oxygen in the cerebral venous blood falls below 19 mmHg. Brain oxygen deprivation leads to accumulation of extracellular potassium and a metabolic crisis as indicated by the depletion of energy substrates and accumulation of lactic acid in the neurons. These effects can occur within a matter of few seconds of inhalation of an anoxic agent. However, it is worthy of note that the survival times of various parts of the brain may differ according to the regional oxygen consumption rate. For example, the survival time of cerebral cortex is considerably shorter than that of the medulla, in which the respiratory centre is located. Normal brain activity may be restored in anoxia-stunned animals if oxygen is administered or they are allowed to breathe atmospheric air. Inevitably, the recovery of consciousness in these animals is rapid. It is therefore a statutory requirement in the United Kingdom that animals must be held within the gaseous atmosphere until they are dead.

Argon and nitrogen, along with xenon, are frequently referred to as inert gases. However, in contrast to argon or nitrogen having anaesthetic properties under hyperbaric conditions, xenon is an anaesthetic gas under normobaric conditions. It has been reported that inhalation of 80% xenon and 20% oxygen induced unconsciousness in humans via the inhibition of _N_-methyl-d-aspartate (NMDA) receptor channels, which are essential for maintaining neuronal excitation during the conscious state. Interestingly, induction of unconsciousness with xenon, argon, nitrogen and nitrous oxide (‘laughing gas’) has frequently been described by humans as a euphoric or very pleasant way of losing consciousness, and this may be due to the effects of those gases on NMDA receptor channels. It is worth noting that the effects of a number of modern analgesics, sedatives and anaesthetics are also mediated via NMDA receptor channels in the brain.

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Polysaccharides for sustainable energy storage – A review

Werner Schlemmer, ... Stefan Spirk, in Carbohydrate Polymers, 2021

3 Batteries-a short historical survey

The first battery was developed in the late 18th century when Luigi Galvani observed a phenomenon he later termed ‘animal electricity’. During the dissection of frog legs he realized that they twitched when the iron scalpel touched them (Galvani & Volta, 1791). However, his friend Alessandro Volta connected these observations to the metal surfaces of the scalpel rather than the frog legs and led the foundation for the invention of the voltaic pile-the first battery. In such a battery, piled copper and zinc disks were assembled. In order to avoid a short circuit, the metals were separated by cloth or cardboard, which were presoaked in an electrolyte solution to ensure conductivity (Dibner, 1964). The battery was fully functioning (stable supply of electricity, current, hardly any self-discharge) but had some disadvantages (electrolyte leakages, short battery lifetime) caused by the weight of the piles and parasitic reactions leading to hydrogen evolution during operation. These issues were solved by the development of the Daniell cell, which had an operating voltage of 1.1 V. This type of cell is based on a zinc anode, and a copper vessel, which was filled with a solution of copper sulfate. Into the vessel, a porous, ceramic tray filled with sulfuric acid was placed which enabled an exchange of ions. Therefore hydrogen evolution was suppressed and over time only conducting copper metal is deposited on the anode (Spencer, Bodner, & Rickard, 2010). The Daniell cell was a major accomplishment in battery technology and its importance can be seen in the unit of the electromotive force (Volt), since the operating voltage of the Daniell cell was roughly 1 V (Hamer, 1965). Later on, different improvements such as the Bird cell (Bird, 1838), Gravity cell and the Poggendorf (Ayrton & Mather, 1911) cell were introduced, which we will not cover in more detail here. It is noteworthy that the Gravity cell was widely used in British and American telegraph networks until the mid 1950s.

The next milestone in battery technology was the development of rechargeable batteries. Until then, battery lifetime was limited by the amount of redox active compounds in the battery. The lead-acid battery was a game changer in this respect. It consists of lead (anode) and lead dioxide (cathode) and uses sulfuric acid as electrolyte. The acid reacts with both electrodes to form lead sulfate causing an electron flow from one electrode to the other, which are both reversible processes, enabling recharging of the battery. Interestingly, the design of the lead-acid battery has not significantly changed since its invention. In some applications, such as in car batteries, they are still in use.

The dry cell technology was the next step towards new application areas of batteries. The basic concept is a paste-like electrolyte, that contains a small amount of moisture to allow for current flow. As the electrolyte is a paste, these cells can be oriented in any direction as there is nothing that could potentially spill off. Portable applications were realized, such as the zinc carbon battery (1.5 V). It is made of a zinc casing that serves at the same time as anode and a manganese(IV) oxide cathode which is connected to a conductive carbon rod. Commonly used gel electrolytes in today’s dry cells contain a moist paste of ammonium or zinc chloride impregnated paper. The paper serves as separator between the zinc anode and the manganese(IV) oxide cathode. This type of cell has a significant market share (roughly 20 %) for portable batteries.

An even larger share of portable batteries is occupied by dry alkaline batteries. In such batteries, zinc and carbon are used with potassium hydroxide as gel electrolyte and a separator, often made from cellulose. The cell features a voltage of 1.4 V and is one of the most commonly used primary batteries with current market shares of roughly 50 %.

In the past two decades, battery development was boosted by several factors. Portable electronics require high energy density while being rechargeable. In addition, battery technology was boosted by massive investments in electric cars.

Lithium ion batteries are capable of delivering voltages of over 3 V while having a high energy density. Developed by G.N. Lewis more than 100 years ago, it took several decades until LIBs became commercially exploitable, with significant efforts of Besenhard and later Goodenough (Besenhard & Eichinger, 1976; Eichinger & Besenhard, 1976; Mizushima, Jones, Wiseman, & Goodenough, 1980). The first commercialized LIB was brought to the market by Sony in 1991. The main advantage of LIBs is that they operate at high voltages, requiring the use of electrolytes other than water, typically ethylene carbonate, propylene carbonate or diethyl carbonate. In such electrolytes, the lithium species are dissolved (e.g. LiPF6, LiBF4). Commercial electrode materials consist of layered oxides, spinels, polyanions (anode) and graphite (cathode). During operation of the battery the lithium ions move to the other electrode, where they intercalate into the electrode material (Fig. 1) (Lu, Han, Li, Hua, & Ouyang, 2013). While LIBs have been used to power consumer electronics for the past 20 years, the increasing number of electrically powered vehicles is driving innovation in this area. However, the past years showed that the current LIB technology features environmental drawbacks ranging from non-sustainable raw material supply (e.g., mining of lithium and cobalt) to challenging recycling. Alternative, evolving battery technologies involve metals such as sodium and magnesium which are highly abundant and available in many places of the world. Their operation is also safer than corresponding lithium ion batteries.

Fig. 1. Schematics of a lithium ion battery using LiCoO2 and graphite as electrode materials.

Reproduced from (Roy & Srivastava, 2015) with permission from The Royal Society of Chemistry.

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Effects of disinfectants on inactivation of mold spores relevant to the food industry: a review

Vincent Visconti, ... Philippe Dantigny, in Fungal Biology Reviews, 2021

Antifungal activity of chlorine dioxide

In their study, Bundgaard-Nielsen and Nielsen (1996) found that 5% chlorine dioxide had a fungicidal efficacy similar to 3% sodium hypochlorite on their selection of target fungi (see §2.3). For 10 min exposure, inactivation values ranged from 2.7 log to more than 5.2 log. Eleven out of 20 isolates exhibited more than 4 log inactivation. All isolates exhibited more than 3 log reduction except Penicillium caseifulvum (2.7 log).

The impact of pH, temperature and humic acid concentration on the fungicidal activity of chlorine dioxide (ClO2) in the range 0.5–3.0 mg/l was assessed on Cladosporium sp., Penicillium sp., and Trichoderma sp. (Wen et al., 2017). The inactivation rate constants for chlorine dioxide, 2 mg/l, were 5, 26 and 17 fold those obtained for chlorine, 2 mg/l, for Cladosporium sp., Penicillium sp., and Trichoderma sp., respectively. Inactivation rate constants were not significantly affected by pH 6 and 7. In contrast to pH, inactivation rate constants decreased significantly by lowering temperature from 27 to 10 °C (by 25% for Penicillium sp. and 50% for Cladoporium sp. and Trichoderma sp.). While the inactivation rate constants did not vary significantly in the 0–2 mg/l humic acid range, inactivation rates at 0.4 mg/l were half those obtained at 0.2 mg/l. Overall, by increasing susceptibility order, the species were ranked Penicillium<Trichoderma<Cladosporium.

As shown in the study of Nierop Groot et al. (2019), chlorine dioxide remained effective against Penicillium spp. at low temperatures. At 7 °C, for 5 min contact time to 500 ppm chlorine dioxide an inactivation greater than 5 log was shown for Penicillium bialowiezense, P. buchwaldii and P. expansum. In comparison, the inactivation obtained by chlorine was 2.5 log in the case of P. bialowiezense and less than 1 log for the two other species. In another study (Okull et al., 2006), P. expansum exposed to chlorine dioxide at 3 ppm for 5 min exposure exhibited 3.7 log inactivation.

Regarding the effect of chlorine dioxide on ascospore-producing species, 10 min exposure to 5% chlorine dioxide led to more than 4.5, more than 4 and 3.3 log inactivation for E. repens (=A. pseudoglaucus), M. ruber and N. pseudofischeri (=A. thermomutatus), respectively (Bundgaard-Nielsen and Nielsen, 1996). Dijksterhuis et al. (2018) also evaluated the fungicidal effect of this biocide on heat-resistant ascospores of Aspergillus fischeri, Paecilomyces variotii, Paecilomyces niveus and Talaromyces macrosporus (=Penicillium macrosporum) which were either dormant or activated by 80 °C heat treatment for 5 min. For the first three mentioned species, the two kind of ascospores were inactivated after 500 and 1000 ppm treatments for 5 min. Only T. macrosporus (=P. macrosporum) ascospores survived up to 500 ppm, but full eradication of this species (i.e. inactivation ≥5 log) was observed after 30 min. During viability assessment experiments, heat activated ascospores of this species showed larger colonies than dormant ascospores, thus suggesting an increased resistance of heat activated ascospores to the disinfectant.

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Biogeochemistry

P. Brimblecombe, in Treatise on Geochemistry, 2003

8.14.11 Anthropogenic Impacts on the Sulfur Cycle

Human activities have vastly affected the sulfur cycle (Brimblecombe et al., 1989). The sulfur released from combustion of fossil fuels for example, exceeds the average natural releases into the atmosphere. Thus sulfur has long been seen as a pollutant central to the acid rain debate of the 1980s. However human progress has had other impacts on the cycle.

8.14.11.1 Combustion Emissions

Sulfur emissions from the combustion of high sulfur coals has been a problem from the thirteenth century when the fossil fuel began to be used in London after the depletion of nearby wood supplies. The intensity of coal use increased reaching its peak within the early twentieth century in Europe and North America. Although the use of coal has declined in these areas, the late twentieth century saw a profound increase in coal use in developing countries, most notably in Asia (see Figure 20). Here emissions have continued to grow with the enormous pressures for industrial development, although changing patterns of fuel use here may lead to decreased emissions in the twenty-first century.

Figure 20. Predicted sulfur emissions from anthropogenic sources (http://sres.ciesin.org).

The combustion of fuels leads to release of SO2 in a simple, but effective oxidation:

S+O2g→SO2g

Many refining and extractive processes release large amounts of air pollution containing SO2. For example, sulfide ores have been roasted in the past with uncontrolled emissions

Ni2S3+4O2→2NiO+3SO2

This sulfur dioxide often destroyed large tracts of vegetation downwind from smelters, such as those at Sudbury in Canada. However, changes in the processes and the construction of a very tall chimney stack have lessened the problems.

The decline in sulfur emissions in Europe and North America has come as part of a shift away from coal as a fuel in all but extremely large industrial plants. Sulfur in coal is about half as pyrites, which is relatively easy to remove, but the rest is organically bound which makes it difficult to remove at an economic rate. Improved controls on stack emissions increasingly rely on the treatment of exhaust gases. In the past this was sometimes by scrubbing the exhaust gas with water to dissolve the SO2, but the late twentieth century saw a range of well-developed methods. The use of lime (calcium hydroxide) or limestone (calcium carbonate) slurries to absorb sulfur dioxide is widely adopted. The main product, calcium sulfate, is notionally not seen as an environmental problem by-product, although it can be contaminated with trace metals. The process is also hampered by the large amounts of lime that can be required. Regenerative desulfurization processes such as the Wellman-Lord procedure absorb SO2 into sodium sulfite solutions converting them to sodium bisulfite. The SO2 is later degassed and can be used as a feedstock for the production of sulfuric acid, for example.

Sulfur is also found in petroleum in organic forms. It can occur at high concentration in some residual oils. This sulfur can be removed by catalytic hydrodesulfurization, but it leads to fuels that tend to become waxy at low temperature. In vehicles catalytic converters have been used to remove nitrogen oxides, carbon monoxide, and hydrocarbons from exhaust streams. However under fuel rich driving cycles (i.e., lots of accelerating and decelerating), hydrogen gas is produced in the exhaust. Three-way catalysts containing cerium dioxide store sulfur from the exhaust stream, under driving conditions, as cerium sulfate. This can at other times be reduced by hydrogen gas to form hydrogen sulfide, which creates a noticeable odor, where traffic is heavy (Watts and Roberts, 1999).

8.14.11.2 Organosulfur Gases

Although the natural sources of organosulfur compounds are best known, there are a number of anthropogenic sources of this class of air pollutant. These are often released from sulfur-rich wastewaters and sewage sludges where DMDS is of particular concern because of its odor problems. MSH and DMS can cause similar problems along with hydrogen sulfide, OCS and carbon disulfide.

OCS is found as a major sulfur compound in anodic gases of commercial aluminum smelters. Studies suggest a specific OCS emission of 1–7 kg t−1 (Al). In 1993 aluminum production was responsible for between 0.02 Tg(S) yr−1 and 0.14 Tg(S) yr−1 of OCS emissions, which is only a small fraction of the annual global budget (Harnisch et al., 1995). Other sources of OCS are coal combustion 0.019 Tg(S) yr−1, industry 0.001 Tg(S) yr−1, the wear on tyres 0.04 Tg(S) yr−1and the combustion products from automobiles 0.002 Tg(S) yr–1 (Kjellstrom, 1998). Carbon disulfide also has a range of anthropogenic sources such as chemical production 0.26 Tg(S) yr−1, industry 0.002 Tg(S) yr−1, aluminum production 0.004 Tg(S) yr−1, and combustion products from automobiles 0.0002 Tg(S) yr−1 (Kjellstrom, 1998).

There are more complex organosulfur compounds associated with the aerosols. Even relatively volatile compounds such as thiophene can bind to particulate materials (Huggins et al., 2000). The emissions from sulfur-containing fuels may be characterized by the presence of dibenzothiophene and benzonaphthothiophene. Coal combustion (notably lignite in an atmospheric fluidized bed) yields a range of heterocyclic compounds containing oxygen, nitrogen, or sulfur, often with three or four rings. The types of sulfur compounds found include: dibenzothiophene, methyldibenzothiophene, dibenzothieno(3,2-b) (1)benzothiophene, benzo(b)napthothiophene, and benzo(2,3)phenanthro-(4,5-bcd) (Stefanova et al., 2002).

Water-soluble organic compounds in urban atmospheric particles can also contain organosulfur compounds. Methanesulfonic acid and hydroxymethanesulfonic acid have been found as the major organosulfur compounds in urban aerosols, most particularly in particles with the diameter range of 0.43–1.1 μm. Monomethyl hydrogen sulfate has also been detected on urban particles from localities where no oil or coal power plant exist (Suzuki et al., 2001).

8.14.11.3 Acid Rain

Rain is naturally acidic because of the weakly acidic carbon dioxide, but the oxidation of sulfur dioxide leads to the much stronger sulfuric acid. The large-scale use of coal caused this to become a problem in nineteenth-century Europe. Remote observations of polluted black rain in Scotland and Scandinavia were made in the late nineteenth century. Some of the most significant early work came from Norway with work of the geologist Waldemar Brøgger and later Amund Helland, who reported on the loss of fish stocks from the 1890s, possibly because of acidification. Modern studies by Knut Dahl and Haakon Torgersen's in the 1920s and 1930s confirmed these observations and the importance of adding lime to reduce the acidity of streams. Rainfall composition was determined by agricultural networks set up to monitor the flux of nutrients to crops in the late nineteenth century. In parallel this also established the impact of combustion processes in the rural environment. The monitoring work recommenced after World War II and gave the information that established the modern picture of acidification of precipitation by the late 1960s. Despite this acid rain did not emerge as a global environmental issue until the 1980s, with concerns over the impact of acidification to the ecosystems across Europe and North America.

The hemispheric changes in precipitation chemistry have been reflected in the records left in high latitude snow, particularly in Greenland. Here the pre-industrial snow shows about equal input of sulfur from marine sources and industrial emissions. From the late nineteenth century, there is evidence of increased anthropogenic impact (Patris et al., 2002), with much of the sulfate arising from North America (Goto-Azuma and Koerner, 2001). The anthropogenic sulfate is sufficient to displace hydrogen chloride from seasalt aerosols such that increasing inputs of anthropogenic HCl can be found in alpine and Arctic ice core records of the twentieth century (Legrand et al., 2002).

The declines in sulfur emissions from the North Atlantic sector have made it is easy for politicians to believe that the acid rain problem has gone away. It is true, emissions here are lower, with a shift away from high sulfur fuels, most particularly coal. In parallel, the amount of sulfur deposited in rain Europe and North America has declined. Indeed, the decline in some parts of the UK and Germany has been so large that crops such as oats and oil seed rape can suffer from sulfur deficiency.

However, the decreases in deposited sulfur are not always matched by equivalent improvements in the amount of acid brought down in rain. Declining sulfur emissions have not always been accompanied by declines in the emission of the nitrogen oxides, which give rise to atmospheric nitric acid in precipitation. Differences in the mode of oxidation that forms nitric acid (a homogeneous oxidation) mean that nitric acid rain has a different geographical distribution to that of sulfuric acid rain. This distribution of acidity can easily change. Furthermore, calcium was once more abundant in dusts and available to neutralize some of the acidity. In recent decades, the amount of alkaline particulate material has declined, perhaps because there is less dust from unsealed roads and less grit from industry and power generation.

However, not all that has been learnt about acid rain in temperate regions is easily applicable in the Asian context. Research and regulation needs to face a different acid rain problem here. Entirely new ecosystem will be confronted by acidic deposition. We have to recognize some of the novel factors along the Asia-Pacific rim have been present for many centuries. Kosa dust and forest fires are a feature of the region, although we know only a little of their history. Alkaline dust offers the potential to buffer acids in rainfall. Forest fires can produce acids, but can also generate large amounts of alkaline ash that disperses along with the acids. However, such neutralization processes are not always well understood. The greater prevalence of acid rain into the tropics, where soils are often deeply weathered, makes available new routes for mobilizing toxic metals within ecosystems.

8.14.11.4 Water and Soil Pollutants

Agriculture and industrial activities have been responsible for doubling the load of sulfate in rivers and the concentrations can be much enhanced in rivers that pass through regions with high anthropogenic activity. In addition, industrial releases sometimes have catastrophic impacts. Examples of such a water pollution incident have occurred when toxic water and tailings from pyrite mining are accidentally released into river basins. In April 1998, releases from a pyrite mine in Aznalcollar, southern Spain, spilled into the Agrio and Guadiamar River Basin affecting some 40 km2. Rapid oxidation meant an increase in concentration and the solubilization of the zinc, cadmium and copper (Simon et al., 2001).

Linear alkylbenzene sulfonates (from detergents) are found in the range 0–5.0 mg kg−1 in both freshwater and marine sediments. Higher levels occasionally found in sediments are associated with untreated sewage effluent (Cavalli et al., 2000).

Benzothiazoles from vulcanization of rubber tires are found so enriched in some situations that they are used as a marker for street run-off water. Thiocyanatomethylthiobenzothiazole used as a fungicide in wood protection and antifouling paints may degrade into benzothiazoles and methylthiobenzothiazole is used in vulcanization processes, so these materials find their way into rivers and ultimately estuaries. Bester et al. (1997) determined the presence of benzothiazole and methylthiobenzothiazole in estuarine and marine waters. Their concentrations range from 0.04 ng L−1 to 1.37 ng L−1. Methylthiobenzothiazole and benzothiazole vary from 0.25 ng L−1 to 2.7 ng L−1 in the North Sea, while 55 ng L−1 methylthiobenzothiazole was found in the Elbe River.

Soils are often sulfur deficient, so sulfur can be added as a fertilizer in agricultural activities. Sulfur can be mobilized by agriculture and rivers readily polluted through the use of sulfur-rich fertilizers (Robinson and Bottrell, 1997). Although this can be added as sulfate, it is readily moved into the soil profile by rain or irrigation. It can also be applied as elemental sulfur, ammonium thiosulfate, and ammonium polysulfide. Ultimately, this fertilizer is likely to appear in runoff waters. Sulfur-containing pesticides now represent a significant input of sulfur to agricultural soils (Killham, 1994) and can pollute runoff waters as mentioned in the section above.

The widespread agricultural use of pesticides increases their concentration in river waters. Many of these contain sulfur, e.g., herbicides thiobencarb (S-4-chlorobenzyl diethylthiocarbamate) isoprothiolane (diisopropyl 1,3-dithiolan-2-ylidenemalonate), diazinon (O–O-diethyl 0-2-isopropyl-6-methylpyrimidin-4-yl) and fenitrothion (O,O-dimethyl O-4-nitro-m-toryl phosphorothioate), fungicide (isoprothiolane) and two insecticides (diazinon and fenitrothion). The concentrations of these pesticides typically show strong seasonal patterns which reflect their use (Sudo et al., 2002).

Thiobencarb controls broad leaf weeds mostly in rice (so much has been used in Japan), lettuce, celery, and endive (894000lbs were used in California in 1997). Thiobencarb may be found at concentrations lower than expected from its application rate and sorption on soil particles (Sudo et al., 2002) and reactions that degrade it. When thiobenzcarb is present at higher concentrations (>1 ppb), a bitter taste in drinking water can be associated with the oxidation product thiobencarb sulfoxide. Other degradation products include 2-hydroxythiobenzcarb (Fan and Alexeeff, 2000) along with 4-chlorobenzaldehyde. The pesticides thiobencarb and ethiofencarb undergo direct photolysis in aqueous solution although thiobencarb yields 4-chlorobenzaldehyde and ethiofencarb gives the expected sulfoxide (Vialaton and Richard, 2000). The sulfur-containing pesticides fenthion and the pollutant from fossil fuels dibenzothiophene can undergo photodegradation typically to the sulfones (Huang and Mabury, 2000a,b).

Windblown sulfates, typically as gypsum, are found in arid regions. Water utilization or agricultural changes can enhance the production of such dusts. The decreasing water volume in the Aral Sea has much enhanced the production of sulfate dusts over recent decades that has become associated with severe environmental problems (O'Hara et al., 2000).

8.14.11.5 Coastal Pollution

Because seawater has high sulfate concentrations, the release of sulfate to coastal waters is not a major problem. However, when organic loads in the discharge waters are heavy, the sulfate can be reduced with a problem of bad odors. A range of larger organosulfides can be found in seawater. Dibenzothiophene is representative of a group of sulfur-containing heterocyclic organic compounds that are common as a form of organosulfur in oils. The relative stability of the dibenzothiophenes has made them useful markers in the weathering of crude oils (Barakat et al., 2001). Dibenzothiophene has been found as a common constituent of coastal sediments with concentrations up to several hundred ng g–1. Sediments of the South China Sea show a concentration range of 11–66 ng g−1 dry sediment. Dibenzothiophene content was higher nearshore relative to offshore sediments, but clay and organic carbon contents appear as two prime factors controlling the sediment dibenzothiophene levels (Yang et al., 1998). The source of this sedimentary dibenzothiophene is generally seen as the deposition of particles from combustion sources. However, it is also possible from crude oil pollution or terrestrial runoff as river sediments can be high in dibenzothiophene (West et al., 1988).

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Role of chitosan and chitosan-based nanoparticles in antioxidant regulation of plants

Anu Singh, ... P.K. Dutta, in Role of Chitosan and Chitosan-Based Nanomaterials in Plant Sciences, 2022

9 Antioxidant regulation of plants

There are several ROS like superoxide ions, hydrogen peroxide, and hydroxyl radicals. Oxygen (O2) is not harmful at the ground state but when it absorbs a large amount of energy, it becomes paramagnetic and very reactive [98]. In the reaction 1O2 is produced then it reduces oxygen to O2•−, H2O2, and •OH. A singlet state of two electrons with opposite spin is formed when a sufficient amount of energy is absorbed by unpaired electrons of the biradical form of oxygen. Triplet chlorophyll formation is favored in light conditions and it activates the synthesis of 1O2 from oxygen molecules [99]. During abiotic stress condition, an insufficient amount of carbon dioxide leads to the formation of 1O2 which cause stomatal closure. Generation of 1O2 during stress conditions results in loss of photosystem II activity that leads to direct oxidation of DNA, unsaturated fatty acids, and protein and causes cell death [100]. 1O2 reacts with deoxyguanosine and modifies nucleic acid [101]. H2O2 production was achieved by gaining only one electron at a time by molecular oxygen and stable intermediate were formed [102]. Nucleophilic O2•− is the short-lived, moderately reactive, primary ROS that can oxidize and reduce [103]. By gaining one electron and two protons it starts producing H2O2. Then disproportionation reaction caused by the superoxide dismutase enzyme converts superoxide ions into H2O2 and O2. Hydrogen peroxide is produced in the electron transport chain of the cell organelles during various abiotic, biotic, and normal stress conditions [104]. H2O2 can cause oxidative damage because it is the only ROS that crosses through aquaporins of biological membrane and travels along with distance within the cell [105]. The major source of H2O2 production is β-oxidation of fatty acid and Photooxidation. The major function of H2O2 is to manage the biological process and handle tolerance against various stress conditions [106,107]. H2O2 is the main cause of the weakening of 50% activity of enzyme-like sedoheptulose-1,7-bisphosphatase, fructose-1,6-bisphosphatase, fructose-1,6-bisphosphatase, and oxidation of phosphatases, protein kinases which results in programmed cell death at high concentration [108]. O2•− and H2O2 both are reactive oxygen species and cause cellular damage but when they transformed into other reactive species, they turned into more harmful species. These reactive species are removed from the cell by CAT and SOD enzymes.

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Cognac: production and aromatic characteristics

L. Lurton, ... G. Snakkers, in Alcoholic Beverages, 2012

11.1 Raw materials, production process and major variants

11.1.1 A product with a long history

Grapevines have been grown in Charentes since the end of the first century ad. In the Middle Ages, thanks to the River Charente, the town of Cognac was already famous for its wine trade, a welcome addition to the salt trade, which had been a major source of income since the eleventh century. Wines from the Poitou vineyards, transported in Dutch ships coming to load up with Atlantic coast salt, were much appreciated in the lands lying alongside the North Sea.

In the sixteenth century, the Dutch began distilling the region’s wines in order to preserve them better. They came to Cognac to seek out the celebrated wines produced in the Champagne and Borderies vineyards, distilling them back at home in order to preserve them. They named the product obtained ‘brandwijn’ (‘burnt wine’) – the origin of the term ‘brandy’.

Double distillation made its appearance in the early seventeenth century, enabling the product to travel in the form of a stable wine spirit a great deal more concentrated than wine itself. The first stills were set up in Charente by the Dutch.

Numerous trading companies sprang up which, in the mid-nineteenth century, began dispatching wine spirit in bottles rather than in casks. This new form of trade gave rise to complementary industries such as glassmaking (which went on to develop local expertise in mechanisation of bottle-manufacturing processes), crate and cork manufacture and printing.

Around 1875 Phylloxera vastatrix, an insect of the hemiptera order, that attacks vines by sucking the sap from their roots, destroyed most of the Cognac vineyards which, by 1893, only covered some 40 600 hectares, as against 280 000 hectares before the phylloxera plague. As elsewhere in Europe, the Charentes vineyards were reconstituted by the use of American rootstocks. This episode led to the creation of the Comité de la Viticulture in 1888, which went on to become the Station Viticole in 1892, an inter-professional qualitative research body devoted to Cognac.

In the first half of the twentieth century, legislation was drawn up in order to conserve longstanding and unchanging local practices:

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1909: delimitation of the geographical production area,

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1936: certification of Cognac as an Appellation d’origine contrôlée (AOC),

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1938: delimitation of regional appellations.

Historically a product for export, nowadays more than 95% of Cognac is consumed outside France, in over 160 different countries. Currently, around 150 million bottles a year are dispatched to waiting markets. For fans from the Far East, via Europe, to the continent of America, Cognac means top-quality wine spirit emblematic of the French art of living.

11.1.2 Current regulations relating to Cognac

With reference to European Regulation N° 110/2008 (European Union, 2008) on the definition, description, presentation and labelling of spirit drinks, Cognac is a wine spirit. The geographical indication ‘Cognac’, along with the complementary geographical indications associated with it, are in Annex III of the same regulation. Under French law, Cognac is an AOC, the rules for production of which are more restrictive than those provided for wine spirits by the aforementioned Regulation, and are laid down in Order no. 2009-1146 of 21 September 2009 by the French Ministry of Agriculture Food and Fisheries (2009).

11.1.3 A delimited geographical production area

Temperate maritime climate

The Cognac winegrowing region enjoys a temperate maritime climate, differing little except in coastal areas, which get more sunshine and experience a narrower range of temperatures. Because the ocean is so close by, rain, although heavier in winter, may fall at any time of the year. Periods of drought are few, ensuring the vine a regular water supply. The average annual temperature stands at around 13 °C, with fairly mild winters. Temperatures are high enough to ensure good maturation of grapes to be used for wine spirit production, but not high enough to burn them. The Cognac region’s climate was described at the beginning of the twentieth century by Ravaz (1900), and later on by Lafon et al. (1964).

A recent study carried out by the BNIC Station Viticole sought to pinpoint recent changes in the Cognac region’s climate and assess their impact on vine growing (Boitaud et al., 2010).

Appellation area delimited into ‘crus’

In the mid-nineteenth century, Henri Coquand (1811–1881) made a study of the Cognac region’s geology (Coquand, 1858). With the help of a taster, he classified the different areas according to the quality of the wine spirits that their soils could produce. Around 1860, their work resulted in the demarcation of different ‘crus’ (growing areas) and served as a basis for the Order of 13 January 1938 delimiting the crus. Geographical denominations, complementary to the Cognac appellation, still make use of their historical names: Grande Champagne, Petite Champagne, Fine Champagne, Borderies, Fins Bois and Bons Bois, to which must be added Bois Ordinaires or Bois à Terroir (Fig. 11.1).

Fig. 11.1. A delimited production area divided into six crus (© BNIC).

According to the work carried out at the time, the dominant characteristics of soils typical of each denomination are as follows:

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Grande and Petite Champagne: thin argilo-calcareous soils over soft chalky Cretaceous limestone,

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Borderies: sandy clay soils containing flint nodules resulting from limestone decarbonation,

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Fins Bois: largely covered by ‘groies’, thin, stony red argilo-calcareous soils, from Jurassic limestone,

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The Bois (Bons Bois, Bois Ordinaires and Bois à Terroirs): sandy soils in coastal areas, certain valleys and over the entire southern part of the winegrowing area. The sand comes from erosion of the Central Massif.

Dumot et al. (1993) give a detailed description of the main types of soil to be found in the Cognac area, which has become a reference in the field.

Wine spirits obtained from the stills are marked by very considerable analytic and organoleptic diversity, largely due to their origin. Such diversity necessitates implementation of different ageing techniques of variable duration.

Grande Champagne produces wine spirits of remarkable finesse, characterised by great distinction and a long finish, and with a predominantly floral bouquet. Its wine spirits are slow to mature, and require long ageing in oak casks in order to reach full maturity.

Petite Champagne wine spirits have mostly the same characteristics as those from Grande Champagne, without, however, the latter’s extreme finesse.

The Borderies produce smooth, rounded wine spirits with a strong bouquet and characterised by an aroma of violets. They have a reputation for reaching optimal quality after shorter maturation than those from the Champagne areas.

Fins Bois produce supple, rounded wine spirits that age quite rapidly and whose fruity bouquet is reminiscent of pressed grapes. Bons Bois produce wine spirits with fruity aromas that age rapidly.

Regulations provide for the indication of the cru (Grande Champagne, Petite Champagne or Borderies, for example) on the label. In such cases, the blend must be ‘single cru’ – in other words, all the products in the blend must come only from the area mentioned on the label. The term Fine Champagne designates a blend of Grande Champagne and Petite Champagne, with at least 50% from Grande Champagne.

11.1.4 Encepagement and vineyard management

Wines destined for elaboration of wine spirits come exclusively from the following grape varieties:

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Colombard B, Folle Blanche B, Montils B, Ugni Blanc B and Semillon B,

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Folignan B, up to 10% of the regional grape varieties.

There are around 75 000 hectares of vineyards devoted to Cognac production. Encepagement is the term used to describe the grape varieties planted within a vineyard. Ugni Blanc is the most commonly planted variety and accounts for almost 98% of vines in the Cognac area. Its rise in Cognac vineyards began following the phylloxera crisis, about a century ago (Ravaz, 1900). A variety originating in Italy, where it is known as ‘Trebbiano Toscano’, the Cognac region is its northern limit for ripening. In the mid-twentieth century, it became the first variety for Cognac production, due to its qualities with regard to productivity (its average yield in the Cognac region is between 120 and 130 hectolitres per hectare), late budding, and production of an acidic wine, low in alcohol content, that is particularly suited to production of quality wine spirits. In 2003, the Bureau National Interprofessionnel du Cognac undertook a major research programme in order to preserve the variety’s genetic diversity (Dumot et al., 2010).

Rules concerning vineyard management also define planting density, distance between rows, pruning, number of buds per hectare, percentage of missing plants, and minimum age of vines.

The management method used by the vine grower enables reinforcement of the required characteristics of high acidity and low alcohol content. Such maturation objectives are specific to wines meant for distillation. High acidity helps wine preservation through the winter months up to distillation, and low alcohol content enables greater concentration of the wines’ aromas in the spirits.

Maximum annual production expressed in pure alcohol per hectare is fixed each year by inter-ministerial order.

11.1.5 An adapted vinification technique

Harvesting of grapes is currently largely mechanised in the Cognac area. Ensuring the grapes’ integrity during the transfer and must-extraction stages is very important for the final quality of the spirits obtained. For this reason, the use of centrifugal pumps with pallets is prohibited for grape transfer. Grapes are pressed immediately after harvesting in traditional horizontal-plate presses or pneumatic presses. Continuous presses with Archimedes screws are prohibited. The musts are immediately transferred into vats for fermentation.

Alcoholic fermentation management is a key factor in ensuring the success of winemaking. The process produces ethanol as well as a large part of the wine’s – and therefore spirit’s – volatile compounds.

Studies on Cognac region yeasts were carried out from the 1970s (Park, 1974; Ribes, 1986) in order to provide producers with strains specifically adapted to distillation wines. In the 1990s, a programme bearing on characterisation and selection of yeast strains naturally present in the Cognac vineyards (Roulland et al., 1995; Versavaud et al., 1995) was carried out. The BNIC defined specifications for selecting the best adapted yeast strains. Six strains currently meet these specifications and are mostly used in the region (Fig. 11.2). In order to increase diversity in production of aromatic compounds, use of several different strains in the same winery is recommended (Ferrari et al., 2010).

Fig. 11.2. Characteristics of the main yeast strains used in the Cognac area.

Use of sulphur dioxide is not authorised during the fermentation of distillation wines. Addition of sulphur dioxide leads to increased production of aldehydes, which would affect the quality of the spirits (Cantagrel et al., 1998). Because of this, so as to minimise wine-preservation risks, the date limit for distillation of wines for Cognac production is set at 31 March of the year following harvesting.

11.1.6 A traditional method of distillation

Distillation of Cognac is determined by:

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The distillation principle implemented: discontinuous distillation or double distillation, also known as ‘_à repasse_’,

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The type of still used: the so-called ‘Charentais’ still, whose shape, material (copper), capacity and heating method have been defined since 1936 and are primordial determining factors for wine spirit quality (Fig. 11.3).

Fig. 11.3. The Charentais still: main components (© BNIC).

This is because:

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The shape of the apparatus contributes to selection of volatile substances,

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Heating by a naked flame generates synthesis of complementary aromas, due to the contact between the wine and the surface of the boiler (cooking phenomenon),

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Still components in contact with the wine, vapours and distillates are made entirely of copper, because of the metal’s physical properties (malleability and good heat conductivity) and its chemical reactivity with different wine constituents.

For each distillation, this type of still requires the carrying out of a highly delicate operation: the ‘coupe’ (cutting). This consists of dividing up the distillate according to its proof and composition in terms of volatile substances, into the ‘heart’ (which will become Cognac) and the parts to be recycled in following distillations (‘heads’, ‘seconds’ and ‘tails’). Depending on wine quality and their qualitative objectives, distillers judge the right moment for cutting along with methods of recycling. Distillation of Cognac therefore remains a manual operation whose success very much depends upon the distiller’s skills.

There are two possible variations to the distillation process for Cognac wine spirits: one concerns the type of wine used in the still, and the other concerns methods of recycling during distillation.

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The distiller can distil either a clear decanted wine or a wine with its lees, i.e. containing the yeasts resulting from alcoholic fermentation. In this case, the distillate acquires a specific aromatic profile, due to higher content of long- and medium-chain fatty acid esters. This type of product is generally matured in casks over longer periods.

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The other variant concerns the distillation method itself, specifically the recycling of the different parts. During the second distillation, the distiller has the choice of recycling the seconds either in a wine or in a ‘brouillis’ (first distillate). The choice calls for different parameters, such as the proof of the wines, seconds and brouillis, and the profile sought. The distillation method is usually included in the specifications laid down with the purchaser.

11.1.7 Strictly controlled ageing

Following distillation, wine spirits to be used for elaboration of Cognac are aged in oak barrels, in the appellation area, for at least two years.

After leaving the still, the new wine spirit stays in oak casks for several years (sometimes even several decades). Ageing of Cognac is a process helped along by the climatic conditions prevalent in the appellation area and by local knowledge developed over the course of the centuries. A range of physicochemical phenomena occur: evaporation of water and alcohol, changes in the concentration of various substances, extraction of compounds produced by wood, oxidation, etc. These phenomena are directed by the spirit’s initial characteristics (proof and acidity), by the type of barrel in which ageing occurs, and by the hygrometric and temperature conditions in the cellars in which the casks are kept (Cantagrel et al., 1993).

During the ageing process, the ‘_eaux-de-vie_’ are exposed to moderately damp conditions and not-too-extreme changes of season. Localisation and construction of cellars are adapted to ensure harmonious ageing. Oaks of Troncais or Limousin types (mainly sessile and pedunculate oak) are used because they enable exchanges to take place over long periods between the wine spirit, the external environment and the wood. In collaboration with Cognac companies, the many cooperages active in the geographical area have developed expertise in the creation of storage conditions best adapted to the ageing of Cognac.

It is up to the Master Blender to select the most appropriate storage conditions depending on the spirits’ initial characteristics, the stage of ageing, and his or her qualitative objectives. The Master Blender also decides when to end the ageing process. Once maturity is reached, he or she transfers the wine spirits into glass demijohns known as ‘Dame-Jeanne’, in which they may remain sheltered from the outside air for decades on end without further development. The oldest eaux-de-vie are stored in a dark storehouse, referred to as ‘Paradise’.

A Cognac wine spirit usually reaches its peak after around 50–60 years of ageing. However, certain eaux-de-vie that have been stored in oak casks a good deal longer (sometimes up to 100 years) can be used in blends in very small quantities, to bring a final touch to the most prestigious Cognacs.

11.1.8 The art of blending

Ageing of Cognac is inseparable from the art of blending. Depending on its elaboration and ageing, every wine spirit has its own aromatic profile, which will be put to full use through its blending with other wine spirits having different characteristics. This crucial and highly complex stage cannot be accomplished through the application of simple technical recipes. The Master Blender depends on empirical knowledge, gained over the course of time and necessitating constant monitoring through tasting, along with a perfect sensory memory of eaux-de-vie at their different stages of elaboration. Such knowledge, which requires many years of apprenticeship under the elders of the profession, has been differentiated, maintained and transmitted through exchanges in the Cognac region’s fabric of companies – between Master Blenders, vine growers, Cognac companies and brokers. On the scientific side, Cantagrel et al. (1991a) have described the development of chemical balances occurring during the blending and reduction of wine spirits.

11.1.9 Ageing designations

As explained above, Cognac must be aged in oak casks for at least two years before being put on the market for direct human consumption. Inventory and age control of all Cognac producers are performed by the Bureau National Interprofessionnel du Cognac (BNIC) (Executive order of July 2003).

The age of an eau-de-vie corresponds to the period during which it has matured in oak casks. In contrast to wine, eau-de-vie virtually ceases to age as soon as it is transferred to a glass container. A Cognac will always be the same age it was when bottled. Ageing designations refer to the age of the youngest component in the blend (Fig. 11.4). It is not the age of the Cognac in the bottle. Cognac companies generally use products much older than the minimum requirement in their blends. Those bearing the most prestigious designations may have aged for decades. Compte ‘0’ begins on 1 April of the year following the harvest. Ageing designations are optional indications, regulated in application of European Community legislation. A decision of the French Government Commissioner to the BNIC (1983 decision) codified the designations to be used, based on the age of the spirits making up the blends:

Fig. 11.4. Cognac ageing counts and designations (© BNIC).

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*** (3-star) or VS (Very Special): The youngest eau-de-vie in the blend is at least two years old (compte 2),

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VSOP (Very Superior Old Pale): The youngest eau-de-vie in the blend is at least four years old (compte 4),

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Napoléon, XO (Extra Old), Extra, Hors d’âge: The youngest eau-de-vie in the blend is at least six years old (compte 6). As of 2016, XO (Extra Old), Extra and Hors d’âge are expected to require compte 10 for the youngest eau-de-vie.

A producer may also create a ‘vintage’ Cognac, although this practice is not very common. In order to do so, he or she must make a request to the BNIC, and a specific traceability of the batch involved right up to its sale has to be set up. The wine spirit so declared must be stored in a separate warehouse and the BNIC carries out regular monitoring until it is marketed. In such vintage Cognacs, the wine spirits used are all produced in the same year, and it is therefore the harvest year that appears on the label (Fig. 11.4).

11.1.10 A well-established typicity

Compliance with the strict set of rules concerning origin and production conditions confers very specific organoleptic and analytic characteristics, a fact that does much to help combat counterfeiting (Mazerolles et al., 1991, 1993), which is one of the BNIC’s main tasks.

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