Eva Tornberg - Academia.edu (original) (raw)

Papers by Eva Tornberg

JUSTIFICATION: Nowadays, there is an increasing interest to recover dietary antioxidants and the ... more JUSTIFICATION: Nowadays, there is an increasing interest to recover dietary antioxidants and the utilization of agricultural by-products as initial sources could be an inexpensive choice. Phenols are a major group of natural antioxidants that occur in all higher plants. Olive mill wastewater (OMW) is a rich source of phenols as it comprises 98 g/100 g of the total phenolic content of the olive fruit and thereby it could be considered as a raw material of great potential. Besides, Olive fruit and OMW are known to contain an appreciable amount of dietary fibers with promising functional properties. OBJECTIVE: The objective of the current study was to develop a novel method for the simultaneous recovery of a dietary fibre containing material and a phenol rich ethanolic extract from thermally concentrated olive mill wastewater (OMW). Thereafter, the recovered materials were investigated for their potentiality to be utilized as food additives. METHODOLOGY: Extraction on thermally concent...

A water soluble dietary fiber containing material was recovered from the olive mill wastewater an... more A water soluble dietary fiber containing material was recovered from the olive mill wastewater and characterized with regard to fiber and ion content. Thereafter, it was utilized as fat replacement in meatballs together or separately with other additives like carrot and compared with regard to the total, water and fat loss or oil uptake during deep fat frying of the meatballs. Results indicated that this material is able to restrict the oil uptake of the meatballs during frying, but it was not able to reduce their water losses. On the other hand, meatballs prepared with this material and additional carrot insoluble fibers possessed both advantages (water holding ability and reduced oil uptake) and thereby they sustained reduced fat content

Olive mill wastewater is a mixture usually comprised of water, organics (sugars, nitrogenous comp... more Olive mill wastewater is a mixture usually comprised of water, organics (sugars, nitrogenous compounds, volatile acids, fats, polyphenols and dietary fibers rich in pectic material) as well as inorganic compounds (mainly potassium salts and phosphates). Pectin and fiber recovery often involves the preparation of an alcohol insoluble material, with the purpose of removing low molecular weight compounds like sugars and phenols. Nevertheless, ethanol could also be used as a surfactant and aids in extraction of pectin material from the insoluble part by penetrating into the capillary porous structure of the fruit tissue. In the current study different concentrations of ethanol up to 20%, together with thermal treatment (80 oC, 25 min) of a concentrated waste sample, were tested prior to the precipitation of the insoluble polymers with boiling ethanol (85%). The extracted material was characterized and compared in relation to the yield per waste dry matter, their water soluble fraction p...

OMW has in this investigation been considered as a raw material for the recovery of valuable comp... more OMW has in this investigation been considered as a raw material for the recovery of valuable compounds like pectin. A study was accomplished for the potential activation of endogenous PME in OMW, as an initial treatment step, prior the recovery of the alcohol insoluble residue (AIR) consisting of pectin. Thus, the temperature activation of PME has been investigated by monitoring the kinetics of the in situ methanol release during thermal treatment up to 3 h at 50-80 oC. Heating of OMW from 50 to 60 oC led to an increasing accumulation of methanol and indicates possible pectin de-esterification. In this temperature range, a linear rate of methanol production was obtained for each temperature. From the corresponding slopes, rates of methanol accumulation were calculated, an Arrhenius plot was constructed and activation energy was calculated to be 144 kJ∙mol-1. This high value compared to other values obtained from similar experiments in vegetables might be related to the high concentr...

As it is well known, dietary fibres play a significant role in many physiological processes and i... more As it is well known, dietary fibres play a significant role in many physiological processes and in the prevention of several diseases. The importance of fibres has led to the development of a large and potential market for fibre-rich food products and gelling agents. Nowadays, there is a trend to find new sources of dietary fibres and the possibility of using undervalued agro-industrial wastes as raw materials is an important economical aspect. Olives are among the fruits with an appreciable amount of fibres and promising functional properties like water holding capacity and cation exchange capacity. Olive mill wastewater is the byproduct of the olive oil production process, which is usually discharged into land and rivers causing severe environmental problems. A research is carried out by Technical University of Crete, Dept. of Environmental Engineering in collaboration with Lund University, Dept. of Food Technology, Engineering and Nutrition, aiming the recovery of valuable ingred...

Food Biophysics, 2007

... Effect of Particle Size and Time Elena Bayod & Pernilla Månsson & Fredrik Innings &am... more ... Effect of Particle Size and Time Elena Bayod & Pernilla Månsson & Fredrik Innings & Björn Bergenståhl & Eva Tornberg Received: 16 March 2007 /Accepted: 10 August 2007 /Published online: 11 September 2007 © Springer Science + Business Media, LLC 2007 ...

Meat Science, 1985

has been utilized to follow non-invasively the post-mortem metabolism of the major phosphorylated... more has been utilized to follow non-invasively the post-mortem metabolism of the major phosphorylated metabolites in muscles from beef slaughter carcasses. In addition to adenosine-5'-triphosphate (ATP), creatine phosphate (CP) and inorganic phosphate (Pi) considerable amounts of glucose-and fructose-6-phosphate ( G6P and F6P, respectively) as well as glycerol-3-phosphate ( Glyc3P) were detected. A TP was mainly present as a Mg 2 ÷-A TP complex. Adenosine-5'-diphosphate (ADP) appeared to be mainly bound to muscle proteins. A good quantitative agreement was found for the levels of ATP, CP and sugar phosphates (SP) when estimated by NMR or enzymatic assays.

Meat Science, 2011

Differently homogenised and heat treated potato pulp, used as a dietary fibre additive in low-fat... more Differently homogenised and heat treated potato pulp, used as a dietary fibre additive in low-fat sausages, gave rise to an enhanced instrumentally and sensory measured firmness and compactness, respectively. This is believed to be due to the high content of insoluble fibre, which creates a fibrous network that enhances the texture of the sausage, while not interfering with the meat protein network. The process and frying losses of the sausages, using potato pulp as an additive, were not significantly different compared to the reference. Comparing the different potato pulp sausages using various kinds of heat treatment of the potato pulp significantly lowered the frying loss and increased the firmness. An explanation to these observations could be that the potato pulp exposed to shorter heat treatment compared with longer gave rise to a lower amount of amylase-leakage from the swelling starch granules caught in the potato pulp matrix.

Journal of Food Science, 2014

The effect of different process stages on microstructural and visual properties of dark chocolate... more The effect of different process stages on microstructural and visual properties of dark chocolate was studied. Samples were obtained at each phase of the manufacture process: mixing, prerefining, refining, conching, and tempering. A laser light diffraction technique and environmental scanning electron microscopy (ESEM) were used to study the particle size distribution (PSD) and to analyze modifications in the network structure. Moreover, colorimetric analyses (L*, h°, and C*) were performed on all samples. Each stage influenced in stronger way the microstructural characteristic of products and above all the PSD. Sauter diameter (D [3.2]) decreased from 5.44 μm of mixed chocolate sample to 3.83 μm, of the refined one. ESEM analysis also revealed wide variations in the network structure of samples during the process, with an increase of the aggregation and contact point between particles from mixing to refining stage. Samples obtained from the conching and tempering were characterized by small PS, and a less dense aggregate structure. From color results, samples with the finest particles, having larger specific surface area and the smallest diameter, appeared lighter and more saturated than those with coarse particles. Final quality of food dispersions is affected by network and particles characteristics. The deep knowledge of the influence of single processing stage on chocolate microstructural properties is useful in order to improve or modify final product characteristics. ESEM and laser diffraction are suitable techniques to study changes in chocolate microstructure.

Meat Science, 2013

Food engineering aspects of cooking of meat products in relation to their biophysical properties,... more Food engineering aspects of cooking of meat products in relation to their biophysical properties, such as water- and fat-holding, have been reviewed. Moreover, some of the new emerging, mild cooking technologies, such as high pressure and electro-based heating (radio frequency cooking and ohmic heating) have been discussed in relation to the biophysical properties of the meat products treated. The holding of the bulk water (about 70% of the muscle weight) was discussed, arguing capillary forces to be one of the dominating mechanisms for this holding, whereas the losses of water and fat (the flow) within the meat are governed by Darcy's law. If we compare the fat-holding in beef burgers and emulsion sausages (frankfurter type) beef burgers lose much larger part of the fat than the emulsion sausages and for the former the fat losses increase with fat content. For emulsion sausages, however, fat losses are independent of fat content and the properties of the fat and the protein matrix are more interrelated. It has been shown experimentally during double sided pan frying of beef burgers that the pressure driven water loss (up to 80% of the water loss) is a substantially more important mechanism governing the water loss than the evaporation losses occurring at the surface crust. Fat losses increased significantly with fat content and were not influenced to any large extent by the cooking temperature and were in the form of drip. By using processing technologies such as high pressure and/or electro-based heating (radio frequency cooking and ohmic heating) a more homogenous heating can be achieved, the reason being volumetric heating. In comparison with conventional heating shorter cooking times were obtained and with smaller temperature gradients lower water- and fat-losses occurred and the yield can be substantially improved. High pressure processing (100-1000MPa) is a preservation technology that allows the reduction of the microbial load at low or moderate temperature. The highest potential application for meat products might be to pressurise finally sealed packages of contaminated sliced high value salami and ham products as the colour of those products can resist high pressure. Ohmic heating is based on the passage of electrical current through a food product having an electrical resistance. For radio-frequency (RF) cooking and micro-wave heating the food product forms a dielectric media between the two electrodes and the heating is caused by the internal friction of the polar molecules. The used frequencies for RF-cooking are lower in the MHz range than for micro-wave heating being in the GHz range.

Meat Science, 1996

s175 S176

Meat Science, 2001

The colour of loin, M. longissimus dorsi (LD), and ham, M. biceps femoris (BF), from pure breed H... more The colour of loin, M. longissimus dorsi (LD), and ham, M. biceps femoris (BF), from pure breed Hampshire, Swedish Landrace and Swedish Yorkshire pigs was studied. The contribution of the pigment content, the myoglobin forms deoxymyoglobin (Mb), oxymyoglobin (MbO) and metmyoglobin (MetMb) and the internal reflectance to the colour of pork of normal meat quality was evaluated using partial least squares regression (PLS). The colour of LD and BF from the Hampshire breed was more red and yellow and more saturated than the colour of the same muscles from the Swedish Landrace and the Swedish Yorkshire breeds. Furthermore, BF from Hampshire was darker than BF from the other two breeds. These differences in colour were related to the lower pH in Hampshire, resulting in more blooming and in higher internal reflectance, and to the higher pigment content. The colour of BF was darker and more red than the colour of LD within each breed. No colour difference was found between gilts and castrates within each breed. Most of the variation (86-90%) in lightness (L* value), redness (a* value) and yellowness (b* value), chroma (saturation) and hue angle of pork of normal meat quality was explained by the pigment content, myoglobin forms and internal reflectance. The L* value, a* value, chroma and hue angle were influenced by both the pigment content and by the myoglobin forms to almost the same extent, while the internal reflectance was of no significance to these colour parameters. The b* value was influenced most by the myoglobin forms, less by the internal reflectance and almost not at all by the pigment content.

Meat Science, 1999

Pairs of muscularis longissimus thoracicus et lumborum (LTL) from young bulls were removed within... more Pairs of muscularis longissimus thoracicus et lumborum (LTL) from young bulls were removed within 1 h of slaughter. Small portions of the muscles were placed in a rigormeter to continously follow the isometric tension and isotonic shortening developed, at constant temperatures of 15, 20, 25, 30 and 35 C, as the muscle went into rigor. The bulk LTL was placed in water baths at the same temperature. One of the bulk pairs was tightly restrained by wrapping, to reduce muscle shortening, the other was unrestrained free to shorten. For the bulk samples, shear values were measured using a Warner±Bratzler instrument (1, 7 and 14 days post mortem), and sensory attributes were measured using a sensory panel (7 and 14 days post mortem). Minimum tension and shortening occurred at 15 C. The activation energy for the muscle shortening process was larger than for the isometric tension process. This indicates that the isometric tension data, collected during rigor, does not solely re¯ect muscle shortening. Thus, a counteracting process that decreases the tension response, most likely ageing is simultaneously detected. Meat that went into rigor at 15 C had least shortening and was always more tender than meat going into rigor at higher temperatures. For meat entering rigor at temperatures higher than 15 C, restraining of the muscle by wrapping, signi®cantly (p<0.05) decreased the amount of muscle shortening and resulted in an improved meat tenderness (p<0.001). It was also observed that at rigor temperatures higher than 15 C the meat tenderness is aected negatively by a reduced ageing capacity. It therefore appears that muscle shortening and enzyme activity both aect tenderness and that both are highly aected by rigor temperature and have the greatest bene®cial eect at a rigor temperature of 15 C. #

Meat Science, 1992

The variations in glycolytic potential (GP, very close to glycogen content) were studied during l... more The variations in glycolytic potential (GP, very close to glycogen content) were studied during lairage in pig m. longissimus dorsi using biopsy sampling. Pigs were sampled on arrival at the abattoor and after treatment. Post-mortem measurements including pH(1), pH(u) and FOP(u) were performed on both longissimus dorsi (LD) and biceps femoris (BF) muscles. The animals underwent one of the following treatments: 2 h lairage mixed or unmixed; 24 h lairage mixed or unmixed with access to water only; 24 h lairage mixed or unmixed with access to a sugar solution. A significant depletion in GP occurred during lairage except when pigs were fed liquid sugar. The extent of this depletion was irrespective of lairage duration or mixing. Pigs lairaged 24 h with access to water only exhibited a significantly lower pH(1) in m. BF suggesting a higher propensity to develop PSE meat. Values of pH(u) were low (pH < 5·5), and did not vary significantly between the treatments since muscle GP remained high, despite the depletion induced by lairage. This was attributed to the high level of muscle glycogen characterizing the Hampshire crossbred pigs used in this experiment. These results suggest that interaction between breed and handling procedure may be important regarding meat pH(u).

Meat Science, 1993

The course of rigor mortis (rigor), ageing and tenderness has been evaluated for three beef muscl... more The course of rigor mortis (rigor), ageing and tenderness has been evaluated for three beef muscles; M. biceps femoris (BF), M. semimembranosus (SM) and M. semitendinosus (ST), when entering rigor at constant temperatures of 15 and 37°C respectively, with and without electrical stimulation (ES/NS) (85 V, 14 Hz and 32 s). The course of post-mortem changes has been registered by isometric tension, by shortening of unrestrained muscle strips and by following the pH decline and the changes in metabolites, such as ATP and CP. Ageing at +4°C was recorded by measuring Warner-Bratzler (W-B) shear values 2, 8 and 15 days post mortem. On the last occasion, the sensory properties of the cooked meat were also evaluated. Maximum shortening and isometric tension were higher at 37°C as compared to 15°C, whereas ES did not reduce rigor shortening. A high correlation between maximum shortening and the ATP-level at the onset of the shortening rapid phase was found (r = 0·77(∗∗∗)), which could explain the greater shortening obtained at 37°C compared to 15°C. Rigor shortening is an important phenomenon governing meat tenderness as tenderness is highly affected by rigor temperature but not by ES. This was the case for muscles SM and ST but not for BF muscle. Even though tenderness was measured after ageing (15 days post mortem), shortening during rigor seems to be more important for toughness when rigor mortis occurs at 37°C than any suggested tenderizing effect due to increased proteolysis in this temperature region.

Meat Science, 1994

This study was performed in order to assess the effect of temperature and differing ultimate pH (... more This study was performed in order to assess the effect of temperature and differing ultimate pH (pH(u), 24 h post mortem) on the development of rigor mortis in pig Longissimus dorsi muscle. The rigor development (isometric tension and shortening) was measured continuously during the first 24 h post mortem, using an apparatus wherein muscle strips were held at constant temperatures of 12 or 35°C. pH(u) was manipulated by adrenaline injections preslaughter. The rates of pH fall, adenosine triphosphate (ATP) and creatine phosphate (CP) breakdown were markedly increased at 35°C compared to 12°C. For both temperatures, no delay phase was observed with regard to the development of shortening. Rigor resulted in higher maximum isometric tension and shortening and in shorter time needed to reach maximum values at 35°C than at 12°C. The results are discussed in connection with pH, ATP and CP data. The extent of ageing from 2 to 4 days post mortem, estimated through myofibrillar length determinations, was higher for 12°C than for 35°C. pH(u) affected significantly most of the traits under study, but its effect depended in some cases upon the rigor temperature. At 12°C, the traits related to the kinetics of rigor development were significantly affected by pH(u), but this was not the case at 35°C. Maximum isometric tension was significantly related to pH(u) at 35°C (r = 0·86, P < 0·001), but such a relationship was not found at 12°C. Myofibrillar lengths were significantly affected by pH(u), but in an opposite manner from one temperature to another. A positive relationship was found at 12°C and a negative one at 35°C. These results illustrate the importance of the interaction between the extent of pH fall and temperature with regard to post-mortem changes in pig muscle.