Luisa Pellegrino - Academia.edu (original) (raw)

Papers by Luisa Pellegrino

Journal of Dairy Research, 1995

SUMMARYThe whole N fraction of six samples of hard and semi-hard pressed cheeses was analysed usi... more SUMMARYThe whole N fraction of six samples of hard and semi-hard pressed cheeses was analysed using PAGE, polyacrylamide gel isoelectric focusing and immuno blotting with polyclonal antibodies against β- and αs1-casein. The origin of some electrophoretic bands corresponding to peptides produced from the enzymic degradation of the casein fractions was established. A number of these peptides were also present in thein vitrohydrolysates of casein with plasmin and chymosin. Thus, it was also possible to determine which casein was the source of each peptide and which enzymes were active in cheese. Compared with the traditional Coomassie staining procedures, immunoblotting is more sensitive and specific, making the interpretation of each electrophoretic profile easy. Thus, it was also possible to obtain a clear picture of the state of each casein fraction in a cheese variety. Two main peptides were isolated from the pH 4·6-insoluble N fraction of Parmigiano-Reggiano using DEAE-cellulose c...

In considerazione delle sovvenzioni previste dalla Comunit\ue0 Economica Europea a sostegno del l... more In considerazione delle sovvenzioni previste dalla Comunit\ue0 Economica Europea a sostegno del latte scremato in polvere (SMP) destinato all\u2019ammasso pubblico, l\u2019aggiunta illecita a questo prodotto di latticello in polvere (BMP), disponibile in abbondanza ed a basso costo negli Stati Membri, si presenta economicamente vantaggiosa ed \ue8 incentivata dalla mancanza di metodi analitici in grado di evidenziarla. Viene proposto un metodo per riconoscere la presenza di BMP nel SMP mediante dosaggio per HPLC della fosfatidilserina (PS) e della fosfatidiletanolammina (PE). L\u2019analisi prevede l\u2019estrazione degli amminofosfolipidi con metanolo, la derivatizzazione automatica con OPA (o-phtalaldeide), la separazione per HPLC in fase inversa su colonna C18 con una corsa di 28minuti e la rilevazione in fluorescenza. Sulla base dell\u2019analisi di numerosi campioni di SMP genuino vengono indicati valori soglia per il contenuto di PS+PE che consentono di riconoscere la presenza \u201csospetta\u201d (P<0.05) o \u201ccerta\u201d (P<0.01) di BMP. Il limite di rilevabilit\ue0 del BMP nel SMP risulta mediamente del 2-3% indipendentemente dalle condizioni di miscelazione utilizzate, solido+solido o liquido+liquido, prima della spraizzazione. Tuttavia causa la variabilit\ue0 del contenuto in amminofosfolipidi, la quantit\ue0 minima rilevabile di BMP pu\uf2 oscillare dall\u20191% al 10% un funzione di origine, condizioni di lavorazione ed et\ue0 dei prodotti utilizzati.Due to the high production of buttermilk in EEC Member States and the aids supported by Community for skimmilk powder (SMP), mixing of buttermilk powders (BMP) with SMP of public storage is economically advantageous and attractive, considering that no analytical methods are available to perform suitable control. A method to recognize buttermilk solids in SMP by quantification of phosphatidylserine (PS) and phosphatidylethanolamine (PE) with HPLC is described. The analysis includes extraction of aminophospholipids with methanol, automatic derivatization with OPA (o-Phtalaldehyde), reverse-phase HPLC on C18 column in a 28 min. run time and fluorescence detection. On the basis of several analyses of pure SMP samples, threshold values for PS + PE content of SMP, allowing to recognize \u201csuspected\u201d (P<0.05) or \u201ccertain\u201d (P<0.01) presence of buttermilk solids are reported. Usually a 2-3% of BMP in SMP is detected in powder samples obtained mixing both solid with solid and liquid with liquid material before drying. However, due to the variability of aminophospholipid content, the minimum detectable amount of buttermilk solids in SMP may range from 1% to 10% according to origin, processing conditions and age of raw material

Molecules

Increasing awareness of balanced diet benefits is boosting the demand for high-protein food and b... more Increasing awareness of balanced diet benefits is boosting the demand for high-protein food and beverages. Sports supplements are often preferred over traditional protein sources to meet the appropriate dietary intake since they are widely available on the market as stable ready-to-eat products. However, the protein components may vary depending on both sources and processing conditions. The protein fraction of five commercial sports supplements was characterized and compared with that of typical industrial ingredients, i.e., whey protein concentrates and isolates and whey powder. The capillary electrophoresis profiles and the amino acid patterns indicated that, in some cases, the protein was extensively glycosylated and the supplemented amino acids did not correspond to those declared on the label by manufacturers. The evaluation by confocal laser scanning microscopy evidenced the presence of large aggregates mainly enforced by covalent crosslinks. The obtained findings suggest tha...

LWT, 2019

Centrifugation is occasionally applied to clean cheese milk, particularly to remove Clostridia's ... more Centrifugation is occasionally applied to clean cheese milk, particularly to remove Clostridia's spores that may cause the "late blowing" of cheese. The sludge separated by centrifugation also contains fat and protein, thus is sterilized and added back to cheese milk. In manufacture of raw milk cheeses, centrifugation shall be performed at temperature below 40 °C and no sterilized sludge can be added to vat milk. Both these limitations negatively affect cheese yield. To evaluate process sustainability, three different centrifugation configurations were tested at a factory producing a traditional raw-milk extra-hard cheese. Either a single or double centrifugation, the latter with two different volumes of discharged sludge, were tested over 3-week periods each. Efficiency of spore removal, decrease of total bacterial count, loss of milk solids and cheese yield were evaluated daily with respect to notcentrifuged milk from the same batch. Double centrifugation with low-volume sludge gave highest efficiency of spore removal, i.e. 98.2 %, while the single process minimized the loss of cheese yield. Impedometric analysis indicated that centrifugation caused a preferential removal of rod-shaped lactic acid bacteria, regardless of configuration. This finding was confirmed by microscopy and suggested that a different bacteria population would operate during cheese ripening.

Journal of Dairy Science, 2019

Automatic milking systems (AMS), first introduced on dairy farms in the 1990s, rapidly spread acr... more Automatic milking systems (AMS), first introduced on dairy farms in the 1990s, rapidly spread across many countries. This technology is based on the voluntary milking of dairy cattle in a completely automated process, which relies on computer management, with a substantial average increase in milking frequency. Compared with conventional milking, AMS significantly alters herd management, with important implications on economic, technical, and social aspects of farming, on animal physiology, health, and well-being. These aspects are explored in an extensive body of research. In contrast, the effects of AMS adoption on milk quality are often overlooked. This review draws together both positive and negative effects of AMS on the milk production chain, particularly emphasizing the variations of hygienic and compositive characteristics of raw milk and their interplay, as compared with milk obtained with conventional milking. Scattered and sometimes conflicting literature exists on whether and how these variations may influence quality and yield of the derived dairy products. Current scientific knowledge on these crucial aspects is thus reviewed, with particular focus on milk technological suitability for being processed into dairy products having the target characteristics in terms of taste, structure, on-storage stability, and sustainability. Provided the managing conditions are optimized, AMS allow increased milk production, mostly due to more frequent milking, without compromising the milk characteristics that are crucial to food industry for processing. Nevertheless, specific biochemical aspects related to the changed milking interval, which determines the duration of enzyme activities and bacterial growth in milk, need further research.

Food Chemistry, 2019

Heat-stable peptidases released in refrigerated raw milk by psychrotrophic bacteria are responsib... more Heat-stable peptidases released in refrigerated raw milk by psychrotrophic bacteria are responsible for UHT milk gelation. K-casein-derived caseinomacropeptides, identified by mass spectrometry, were constantly detected in gelled milk by capillary electrophoresis. Strains of Pseudomonas fluorescens, Ps. poae and Chryseobacterium joostei, selected among aprX-positive strains from raw milk, were incubated in milk up to 6 days at 4 °C before sterilization (98 °C/4 min). Samples were then stored at 25 or 40 °C, visually observed for gelation, and analysed for presence of caseinomacropeptides throughout 90 days of storage. Depending on cold pre-incubation time, caseinomacropeptides accumulated well before gelation onset in milk stored at 25 °C. Caseinomacropeptides were successively degraded, especially in milk stored at 40 °C, due to extensive proteolysis, and an abundant sediment developed instead of a gel. The caseinomacropeptides are here presented as an early indicator of UHT milk gelation and a mechanism explaining this phenomenon is proposed.

Journal of Dairy Science, 2018

Effect of temperature on the microstructure of fat globules and the immunoglobulin-mediated inter... more Effect of temperature on the microstructure of fat globules and the immunoglobulin-mediated interactions between fat and bacteria in natural raw milk creaming D'Incecco, 2017. Natural creaming, the first step of Grana Padano and Parmigiano Reggiano cheese making, can be carried out at varying temperatures to maximize skimming. This work shows how selected temperatures, or successive combinations of temperature, change the microstructure of fat globules, a factor known to affect final cheese microstructure. This study also identifies the immunoglobulin classes that mediate interactions between fat globules and bacteria, helping to explain the naturally occurring variations in milk debacterization during creaming and offering a route to optimize debacterization. Overall, this study will help cheesemakers optimize creaming and decrease late blowing defects in ripened cheese. 2 RUNNING HEAD: INTERACTIONS OF FAT GLOBULES IN RAW MILK CREAMING Effect of temperature on the microstructure of fat globules and the immunoglobulin-mediated interactions between fat and bacteria in natural raw milk creaming

Food Research International, 2018

Consiglio per la ricerca in Agricoltura e l'analisi dell'economia agraria, CREA-ZA Via A.

Istituto Lombardo - Accademia di Scienze e Lettere - Incontri di Studio, 2018

Milk is a complex system where lipids, proteins, sugars and salts are present in different phases... more Milk is a complex system where lipids, proteins, sugars and salts are present in different phases, and thus shows a characteristic behaviour during either technological treatments or storage. Lipids are organized as globules, small drops of triglycerides surrounded by a biological membrane that ensures stability of their emulsion. Casein is the main milk protein and is organized as micelles containing salts and strongly hydrated. This last feature has an important effect on the micelle stability. Furthermore, micelle stability is ensured by glycosylated k-casein fragments. Interaction between fat globules and casein micelles are likely to occur since ~1010 globules e 1014 micelles are present in 1 mL of milk and their reactive surface is approximately 0.07 and 4 m2 respectively. Different milk processes, i.e. mechanic or thermal, are responsible for interactions which may vary in number and chemical nature. Microscopy techniques represent an indispensable tool to study milk microstr...

Food Analytical Methods, 2017

Although free amino acids (FAAs) represent a significant component of ripened cheeses and can pro... more Although free amino acids (FAAs) represent a significant component of ripened cheeses and can provide useful information for their characterization, no inter-laboratory validated analytical method exists which allows a reliable comparison of data obtained by different laboratories and the adoption of quality control schemes based on FAA pattern. The objective of the present work was to test the effectiveness of an analytical protocol for the determination of the FAA composition of cheese and to verify the adequateness of this type of analysis for quality control procedures of Grana Padano PDO cheese as well as for research purposes. After an initial test to compare performances of ion-exchange chromatography (IEC) and HPLC techniques, an inter-laboratory collaborative study (seven laboratories, four samples) was organized to validate an IEC method with post-column ninhydrin derivatization and using L-norleucine as an internal standard. Determined amounts of individual FAA ranged from 8 to over 1380 mg/100 g cheese, with relative standard deviation of repeatability (RSD r) ranging from 0.5 to 4.6%, and relative standard deviation of reproducibility (RSD R) ranging from 1.3 to 9.9% for FAA concentrations over 100 mg/100 g. For lower concentrations, RSD r and RSD R were about thrice as high. On the basis of the results of this investigation, at present, the validated method is adopted as the official method for the determination of FAA patterns in the quality control of Grana Padano PDO cheese.

LWT, 2018

The late blowing defect still represents a problem for hard cheeses. Thus, the behaviour of the c... more The late blowing defect still represents a problem for hard cheeses. Thus, the behaviour of the cheese spoiling bacterium C. tyrobutyricum was studied throughout the cheesemaking and ripening of Grana Padano using an innovative approach. Cells and spores, independently sealed within dialysis tubes, were kept in the vat during the entire cheesemaking and then into cheese until 6-2 month ripening. At each sampling step, morphological changes of cells and spores were monitored by electron microscopy and supported with plate counts. Vegetative cells died during curd cooking and then were no longer cultivable. However, 2 x 10 2 spores appeared at the end of this stage, likely triggered by the exponential growth phase, and were present until 6-month ripening. In cheese, C. tyrobutyricum UC7086 proved to convert free arginine to citrulline and then to ornithine, and to produce γ-aminobutyric acid by glutamate transamination rather than by decarboxylation. Compartmentalization of vegetative cells and spores into dialysis tubes was effective in studying their respective behaviour in a real cheesemaking. This approach allowed to demonstrate that the number of vegetative cells in milk in addition to that of spores should be considered for the eradication of the late blowing defect.

Journal of Agricultural and Food Chemistry, 2016

A set of 191 strains of Streptococcus thermophilus were preliminarily screened for the presence o... more A set of 191 strains of Streptococcus thermophilus were preliminarily screened for the presence of the genes codifying for cell envelope-associated proteinase (prtS), and for glutamate decarboxylase (gadB) responsible for γ-aminobutyric acid (GABA) production. Growth and proteolytic activity of the gadB positive strains (nine presenting the prtS gene and 11 lacking it) were studied in microfiltered pasteurized milk. Degradation of both caseins (capillary electrophoresis) and soluble nitrogen fractions (HPLC), and changes in the profile of free amino acids (FAA, ion-exchange chromatography) were evaluated at inoculation and after 6 and 24 hours incubation at 41°C. None of the strains was capable of hydrolyzing caseins and βlactoglobulin and only two hydrolyzed part of α-lactalbumin, these proteins being present in their native states in pasteurized milk. Contrariwise, most strains were able to hydrolyze peptones and peptides. For initial growth, most strains relied on the FAA present in milk, whereas, after 6 hours, prtS + strains released variable amounts of FAA. One prtS + strain expressed a PrtS-phenotype and two prtSstrains showed a rather intense proteolytic activity. Only five strains (all prtS +) produced GABA, in variable quantities (up to 100 mg/L) and at different rates, depending on the acidification strength. Addition of glutamate did not induce production of GABA in non-producing strains that, however, unexpectedly showed to adopt the degradation of arginine into citrulline and ornithine as an alternative acid resistance system and likely as a source of ATP.

Viene studiata la possibilit\ue0 di creare modelli chemometrica atti a tipizzare il formaggio Pro... more Viene studiata la possibilit\ue0 di creare modelli chemometrica atti a tipizzare il formaggio Provolone, determinandone il quadro in amminoacidi liberi ed elaborando statisticamente I dati. Sono state analizzate complessivamente 53 forme di Provolone, sia di et\ue0 ed origine note che del commercio, e sono stati utilizzati criteri di elaborazione statistica descrittiva ed analisi delle componenti principali. Diversamente a quanto riscontrato per il formaggio Parmigiano-Reggiano, il contenuto quali-quantitativo in amminoacidi liberi del Provolone si dimostra molto variabile anche per forme della medesima et\ue0 e di uguali caratteristiche merceologiche (pezzatura, prodotto dolce o piccante), tanto che non si evidenzia alcun modello chemometrico capace di tipizzare questo formaggio sulla base del suo pattern amminoacidico. S\u2019intravede tuttavia la possibilit\ue0 di valutare il periodo di maturazione di forme della medesima pezzatura e di caratterizzare la produzione di determinati caseifici, sulla base del contenuto totale in amminoacidi liberi espresso sulle proteine totali e del contenuto relativo di alcuni di essi quali Glutammina, Istidine, Arginia e Acido gamma-Amminobutirrico. Analisi statistica descrittiva ed analisi delle componenti principali conducono alle medesin\uecme conclusioni, confermando che la tipizzazione chimico-analitica del formaggio Provolone, e dunque la sua difesa da produzioni similari, sar\ue0 possibile solo quando uno standard di qualit\ue0 preciser\ue0 caratteristiche merceologiche e condizioni di lavorazione di questo tipico formaggio italiano.An attempt was made to create chemometric models characterizing Provolone cheese by determining its free amino acid (aa) pattern and evaluating the data with different statistic criteria. 12 commercial samples sold as \u201cProvolone\u201d and 41 typical Provolone cheeses of known age and origin, obtained from dairies under control of the \u201cConsorzio per la Tutela del Formaggio Provolone\u201d were analyzed for their free aa content. Statistical evaluation of the data and related graphic models are presented Unlike Parmigiano-Reggiano, Provolone cheese, even at a same ripening period, shows great variability both in free aa content and in their relative ratios, due mainly to differences in the commercial quality, but probably also to different processing and ripening conditions. Therefor no analytical models based on free aa composition and capable to characterize Provolone cheese can be presently suggested. Nevertheless, parameters based on the total free aa content, expressed as percentage of total protein, and on the relative contents of single free aa like GLN, HIS, ARG, GABA allow both to estimate approximately the ripening period of Provolone cheeses of the same size and to characterize the production of single dairies

Italian Journal of Food Science

$Research paper thumbnail of Changes in the soluble nitrogen fraction of milk throughout PDO Grana Padano cheese-making$

International Dairy Journal, 2015

The behavior of soluble nitrogen compounds during Grana Padano cheese-making was studied at eight... more The behavior of soluble nitrogen compounds during Grana Padano cheese-making was studied at eight dairies. Raw milk, skimmed milk, sweet whey and the derived natural whey culture, collected from 24 processes, were analyzed for soluble whey proteins (α-La and β-Lg), proteose-peptones (PP), small peptides (SP), caseinomacropeptides (CMPs), and free amino acids (FAA). The PP fraction increased during milk natural creaming, then part of it was selectively retained in the curd and the rest degraded in the first few hours of whey fermentation, together with α-La, CMPs and part of SP. Features outlined for the whey culture have been confirmed on 30 samples collected at six different dairies. A time course study of the whey fermentation showed that degradation of α-La begins when the pH drops below 4, whereas β-Lg content did not change. Uptake of specific FAA is shown to support the initial growth of lactic acid bacteria in whey.

Advanced Dairy Chemistry, 2012

ABSTRACT The first part of this chapter outlines general aspects concerning dietary proteins, i.e... more ABSTRACT The first part of this chapter outlines general aspects concerning dietary proteins, i.e. protein requirements in human diet, role and nutritional quality of proteins and methods for its evaluation (CS, Protein Digestibility Corrected AA Score [PDCAAS]), protein digestibility and efficiency of protein utilisation. The second part specifically focusses on the amino acid composition and nutritional properties of milk proteins, the peptides and amino acids deriving from their digestion (protein turnover, regulation of gastrointestinal function and antibody production, cell signalling) and the effects of milk processing on these properties. This chapter concludes with an overview of functional foods obtained from specific milk proteins.

International Dairy Journal, 2010

Different chemical indices related to proteolysis and ripening time have been investigated in Gra... more Different chemical indices related to proteolysis and ripening time have been investigated in Grana Padano (n ¼ 155) and Parmigiano-Reggiano (n ¼ 27) cheese samples using ion-exchange chromatography and capillary electrophoresis. Levels of intact caseins, g-casein and free amino acids in cheese were not strictly related to the maturation period, varying among samples of the same age. A peptide, identified by HPLC/electrospray ionization-mass spectrometry as pyroglutamyl-g 3-casein, resulted from cyclisation of N-terminal glutamic acid into a pyroglutamic acid residue. Based on the peak area ratio of pyroglutamyl-g 3-casein and g 3-casein, an equation, suitable for determination of the cheese age, is proposed. The commercial classes of Grana Padano ripened over 16 and 20 months can be identified by adopting a minimum threshold value for this peak area ratio.

Le Lait, 1997

A centripetal temperature gradient takes place in Grana Padano (GP) during moulding because of th... more A centripetal temperature gradient takes place in Grana Padano (GP) during moulding because of the slow heat transfer within the cheese and the fast cooling of the outer part. This gradient, in combination with the low pH value, induces a centripetal inactivation of alkaline phosphatase (ALP). Throughout the ripening process, the activity of the enzyme keeps > 3 10 5 mU/kg cheese in the peripheral zones and < 300 mU in the core. The objective of the present study was to determine whether the presence of heat load gradients and ALP inactivation improves the analytical distinction between GP and imitation hard cheeses and affects the ripening behaviour. DifferentIy ripened sampies of traditional GP, grana cheese of reduced size, or made from pasteurized milk following GP technology, or collected at the market were submitted to a stratigraphie study. For each cheese sample, subsequent portions collected from the rind to the core were analyzed for moi sture and water activity, a w ' ALP activity, furosine, free ami no acids (FAA), casein phosphopeptides (CPPs) and free fatty acids (FFA). Regarding cheese characterization, thermal treatments of cheese milk can be recognized in GP only by determining the enzyme activity in the most peripheral portions. When the size of the cheese is reduced, cooling in moulding is faster and ALP inactivation in the core is lower. When the moulded cheese is heated, inactivation of the enzyme also takes place in the outer parts. The furosine values, which describe the extent of heat load in dairy systems, increase from the outer part to the GP core (from 10 mg to 60 mg/lOO g protein). This gradient is unaffected by prolonged ripening, but changes when modifications in technoIogical parameters such as pasteurization of milk, forced heating in moulding and reduction of cheese size are introduced. The distribution of ALP and furosine values within the cheese constitutes a distinctive parameter between GP and its imitation products. Regarding chee se ripening, ail the values of chemical indices adopted for describing the ripening of GP show a progressive increase from the inner to the outer portions of nine-or 15month-old chee se samples. These patterns are more pronounced for most of the FAA, and are marked for free serine which increases in the outer zones up to 50% more than in the core. The amount of 'enzyme resistant' CPP~-CN(f16-22)3P, the accumulation of whieh requires the presence of active phosphatases and aminopeptidases, has the same stratigraphie behaviour as that of FAA. The close Oral communication at the IDF Symposium 'Ripening and Quality of Cheeses',

Scienza e Tecnica …, 1993

... espressa in percentuale relativa, soprattutto per campioni con pari "intensita prote... more ... espressa in percentuale relativa, soprattutto per campioni con pari "intensita proteolitica". Cio consente di individuare un modello chemometrico bidimensionale atto a caratterizzare il GP e basato sullelaborazione matematica del contenuto relativo di alcuni AA LIB. ...

Foods, 2020

Extending ripening of hard cheeses well beyond the traditional ripening period is becoming increa... more Extending ripening of hard cheeses well beyond the traditional ripening period is becoming increasingly popular, although little is known about the actual evolution of their characteristics. The present work aimed at investigating selected traits of Parmigiano Reggiano cheese ripened for 12, 18, 24, 30, 40 and 50 months. Two cheeses per each ripening period were sampled. Although moisture constantly decreased and was close to 25% in 50-month cheeses, with a parallel increase in cheese hardness, several biochemical changes occurred involving the activity of both native and microbial enzymes. Capillary electrophoresis demonstrated degradation of αs1- and β-casein, indicating residual activity of both chymosin and plasmin. Similarly, continuous release of free amino acids supported the activity of peptidases deriving from lysed bacterial cells. Volatile flavor compounds, such as short-chain fatty acids and some derived ketones, alcohols and esters, evaluated by gas chromatography with ...