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International audience; To meet current societal demand for more sustainable transformation processes and bioresources, these processes must be optimized and new ones developed. The evolution of various systems (raw material, food, or process attributes) can be predicted to optimize the uses of biomass for better quality, safety, economic benefit, and sustainability. Predictive modeling can guide the necessary changes and influence industrials, governmental policies and consumers decision-making. However, achieving good predictive capability requires reflection on the models and model validation, which can be difficult. This review aims to help scientists begin to predict by presenting the techniques currently used in predictive science for food and related bioproducts. First, a guideline helps readers initiate a prediction process along with final tips and a warning about the risks involved, with a particular focus on the crucial validation step. Threebroad categories of techniques are then presented: empirical, mechanistic, and artificial intelligence (or “data-driven”). For each category, the advantages and limitations of current techniques for prediction are explained in light of their current domains of applications, illustrated with literature studies and a detailed example. Thus this article provides engineering researchers information about predictive modeling which is a recent relevant development in optimization of both food and nonfood bioresources processes.Practical applications Predictive modeling is a recent development of much relevance in the optimizationof both food and nonfood bioresources processes. The goal of this article is to guide those in research or industry who would like to start predicting. Therefore, the article is intended as a primer on prediction concepts and predictive techniques for food and non-food bioresources processing. Three categories of techniques commonly used in these fields are illustrated by various examples of current applications and amore detailed example helps to understand the implementation process. An increased ability of the global scientific body to predict the outcome of various decisions, often linked or sequential, will open new avenues for designing food products with circularity in mind: maintaining value and not creating waste in the process.

To move today’s agricultural and urban systems towards tomorrow’s circular economy and respond to climate change, it is imperative to turn organic residues and wastewater into resourceful assets. This article discusses the changes that are needed in research to drive this paradigm shift and to go from a “losses and waste” situation to a “resource and opportunities” ambition. The current lines of research aim to maximise the use and value of biomass or organic residues and wastewater and propose new organisational schemes driven by technical innovations. Exploring the pathways to a sustainable future through many domains let us identify five challenges to structure the research efforts and find circular bioeconomy solutions for organic residues and wastewater: (1) proposing innovative processes and integrated multi-process systems; (2) promoting the emergence of multi-scale and cross-sectoral organisations; (3) developing multi-performance evaluation methods, (4) rethinking research–society intersections, and (5) enhancing research–legislation interactions. We end by outlining prospects for moving forward past current limitations: beyond increasing knowledge, research will continue its own transition. Our responsibility today is not to think about what we could do for a better world but what we should do to make our ever-changing world even better and more sustainable. Graphic Abstract

International audience; AbstractThere is a growing demand for moving towards sustainable agri-food systems which per nature covers a complex network of activities and domains; such systems will benefit from multi-criteria decision analysis (MCDA) methods. Although some reviews on MCDA in agri-food research have been published, none of them covered the whole value chain. In this article, a corpus of 954 articles published by INRA scientists from 2007 to 2017 was used to study the diversity and potentiality of MCDA techniques. For the first time, experts from more than 10 agri-food domains worked altogether to annotate the articles, carry out a multivariate analysis, and finally interpret the statistical results to identify the specificities of certain domains and the complementarities between domains and to suggest avenues for future agri-food research. One-third of the studies were based only on a list of indicators, even when their purpose was to choose, sort, or rank options. Regardless of the scientific discipline in the agri-food sector, MCDA studies rarely considered temporal dynamics, spatial scale changes, or stakeholder contributions. As the agri-food system becomes increasingly sustainable in the near future, the use of MCDA methods will accelerate. To become more effective, they will have to include ecosystem services, even outside the scope of ecological studies. Similarly, MCDA studies will need to include participatory science to involve stakeholders (i.e., public authorities, governmental agencies) and end-users (i.e., farmers, producers, industrials, consumers) in the construction of the multi-criteria evaluation but also in the resulting decisions.

WOS: 000462482100001, PubMed ID: 30886367, Developing a mechanistic understanding of the impact of food structure and composition on human health has increasingly involved simulating digestion in the upper gastrointestinal tract. These simulations have used a wide range of different conditions that often have very little physiological relevance, and this impedes the meaningful comparison of results. The standardized protocol presented here is based on an international consensus developed by the COST INFOGEST network. The method is designed to be used with standard laboratory equipment and requires limited experience to encourage a wide range of researchers to adopt it. It is a static digestion method that uses constant ratios of meal to digestive fluids and a constant pH for each step of digestion. This makes the method simple to use but not suitable for simulating digestion kinetics. Using this method, food samples are subjected to sequential oral, gastric and intestinal digestion while parameters such as electrolytes, enzymes, bile, dilution, pH and time of digestion are based on available physiological data. This amended and improved digestion method (INFOGEST 2.0) avoids challenges associated with the original method, such as the inclusion of the oral phase and the use of gastric lipase. The method can be used to assess the endpoints resulting from digestion of foods by analyzing the digestion products (e.g., peptides/amino acids, fatty acids, simple sugars) and evaluating the release of micronutrients from the food matrix. The whole protocol can be completed in similar to 7 d, including similar to 5 d required for the determination of enzyme activities., COST actionEuropean Cooperation in Science and Technology (COST) [FA1005 INFOGEST26]; French National Institute for Agricultural Research (INRA)Institut National de la Recherche Agronomique (INRA), We acknowledge COST action FA1005 INFOGEST26 (http://www.cost-infogest.eu/) for providing funding for travel, meetings and conferences (2011-2015). We acknowledge the French National Institute for Agricultural Research (INRA, http://www.inra.fr) for its continuous support of the INFOGEST network by organizing and co-funding the International Conference on Food Digestion and workgroup meetings. We thank A.G.F. Lopes (Universidade de Lisboa, Portugal) and V.S.N. Mishra (Teagasc Food Research Centre, Moorepark, Ireland) for their help in the final preparation of the videos. We also acknowledge the many other researchers, mostly associated with the above COST action and subsequent events, who have contributed to the discussion of digestion parameters.

Several studies demonstrated that fermented milks may provide a large number of bioactive peptides into the gastrointestinal tract. We previously showed that beta-casomorphin-7, an opioid-like peptide produced from bovine β-casein, strongly stimulates intestinal mucin production in ex vivo and in vitro models, suggesting the potential benefit of milk bioactive peptides on intestinal protection. In the present study, we tested the hypothesis that the total peptide pool (TPP) from a fermented milk (yoghurt) may act on human intestinal mucus-producing cells (HT29-MTX) to induce mucin expression. Our aim was then to identify the peptide(s) carrying the biological activity and to study its impact in vivo on factors involved in gut protection after oral administration to rat pups (once a day, 9 consecutive days). TPP stimulated MUC2 and MUC4 gene expression as well as mucin secretion in HT29-MTX cells. Among the four peptide fractions that were separated by preparative reversed-phase high-performance liquid chromatography, only the C2 fraction was able to mimic the in vitro effect of TPP. Interestingly, the sequence [94-123] of β-casein, present only in C2 fraction, also regulated mucin production in HT29-MTX cells. Oral administration of this peptide to rat pups enhanced the number of goblet cells and Paneth cells along the small intestine. These effects were associated with a higher expression of intestinal mucins (Muc2 and Muc4) and of antibacterial factors (lysozyme, rdefa5). We conclude that the peptide β-CN(94-123) present in yoghurts may maintain or restore intestinal homeostasis and could play an important role in protection against damaging agents of the intestinal lumen.

Caseinophosphopeptides (CPPs) are bioactive peptides originating from proteolysis of caseins, the main proteins of milk. In this study, the generation of CCPs during Beaufort cheese making and by in vitro simulated gastro-intestinal hydrolysis using pepsin and pancreatin were assessed using selective precipitation and liquid chromatography–electrospray ionisation tandem mass spectrometry. Seventy-two water-soluble CPPs, mainly originating from β-casein, were identified in Beaufort cheese, while 79 CPPs, mainly generated from α s1 -caseins, were obtained from enzymatic hydrolysates. Most of the peptides generated by the action of digestive enzymes were monophosphorylated; however, 17 out of the 23 polyphosphorylated CPPs identified from digested Beaufort cheese still contained the characteristic cluster sequence Ser(P)-Ser(P)-Ser(P)-Glu-Glu, providing calcium-binding properties to CPPs. The content of CPPs in Beaufort cheese before and after the action of digestive enzymes was estimated to be 230 and 275 mg per 100 g of fresh cheese, respectively. The action of proteolytic digestive enzymes on CPPs is discussed.

Caseinophosphopeptides (CPP) are food mineral-rich components that may resist intestinal enzyme hydrolysis. We wondered whether phosphorylation and/or mineral binding induces resistance of CPP to intestinal hydrolysis. We used intestinal brush-border membrane vesicles to digest different forms of the beta-casein (1-25) peptide: unphosphorylated and phosphorylated carrier of varied cations. The results showed that the activity of alkaline phosphatase seems not to be specific to either the phosphorylation degree or the phosphorylation sites whereas phosphorylations limited the action of peptidases. Studying the mechanism and the kinetics of hydrolysis of the different peptides allows understanding how some cations prevent more CPP from hydrolysis than others. The action of both exo- and endopeptidases was limited for the beta-CN (1-25) peptide bound to zinc or copper. Actually the peptide bound to copper was almost not hydrolyzed during the digestion, suggesting that coordination bond of copper to CPP inhibits the action of both phosphatase and peptidases.

We recently reported the identification of a peptide from yoghurts with promising potential for intestinal health: the sequence (94-123) of bovine β-casein. This peptide, composed of 30 amino acid residues, maintains intestinal homoeostasis through production of the secreted mucin MUC2 and of the transmembrane-associated mucin MUC4. Our study aimed to search for the minimal sequence responsible for the biological activity of β-CN(94-123) by using several strategies based on (i) known bioactive peptides encrypted in β-CN(94-123), (ii) in silico prediction of peptides reactivity and (iii) digestion of β-CN(94-123) by enzymes of intestinal brush border membranes. The revealed sequences were tested in vitro on human intestinal mucus-producing HT29-MTX cells. We demonstrated that β-CN(108-113) (an ACE-inhibitory peptide) and β-CN(114-119) (an opioid peptide named neocasomorphin-6) up-regulated MUC4 expression whereas levels of the secreted mucins MUC2 and MUC5AC remained unchanged. The digestion of β-CN(94-123) by intestinal enzymes showed that the peptides β-CN(94-108) and β-CN(117-123) were present throughout 1·5 to 3 h of digestion, respectively. These two peptides raised MUC5AC expression while β-CN(117-123) also induced a decrease in the level of MUC2 mRNA and protein. In addition, this inhibitory effect was reproduced in airway epithelial cells. In conclusion, β-CN(94-123) is a multifunctional molecule but only the sequence of 30 amino acids has a stimulating effect on the production of MUC2, a crucial factor of intestinal protection.

Digestion of proteins leads to the release of numerous peptides in the gastrointestinal tract, among them several bioactive peptides. This review compiles, organises and critically analyses the information available on bioactive peptides present in vivo in the digestive tract of adult humans and animals. It focuses on milk proteins, which are recognised as one of the main sources of bioactive peptides with different biological functions. To date, few studies have been performed on the presence of milk-derived peptides in the intestinal tract in vivo. The diversity of these studies is remarkable in terms of the milk products that have been tested, the animal models selected and the segment of the digestive tract considered. Altogether, 69 bioactive peptides identified in vivo are reviewed. Most of them are released from casein, and especially from β-casein, to which 38 bioactive peptides are attributed. These sequences can be classified mainly as angiotensin-converting enzyme (ACE) inhibitors, opioids and antimicrobial peptides. Particular attention is paid to β-casomorphins and caseinomacropeptide-derived peptides. The function of caseinophosphopeptides as a mineral carrier is also discussed. Few bioactive peptides derive from whey proteins., The authors are involved in the Food and Agriculture COST (European Cooperation in Science and Technology) Action FA1005 “Improving health properties of food by sharing our knowledge on the digestive process” (INFOGEST)

By studying the hydrolysis of -casein during soft cheese manufacture, we demonstrated that this casein was hydrolysed before renneting during milk maturation. The quantitative time course of the peptides -CN (f161-169) and -CN (f162-169) was determined throughout the drainage, and the CMP was sought out within the milk before inoculation and before renneting. In this way, we showed that before renneting, the lactococcal cell envelope proteinase produced the peptide -CN (f161-169) mainly from -casein, if not all, whereas the peptide -CN (f162-169) originated from CMP through the action of chymosin. -casein / lactococcal starter / milk maturation / soft cheese

WOS: 000336842300006, PubMed ID: 24803111, Simulated gastro-intestinal digestion is widely employed in many fields of food and nutritional sciences, as conducting human trials are often costly, resource intensive, and ethically disputable. As a consequence, in vitro alternatives that determine endpoints such as the bioaccessibility of nutrients and non-nutrients or the digestibility of macronutrients (e. g. lipids, proteins and carbohydrates) are used for screening and building new hypotheses. Various digestion models have been proposed, often impeding the possibility to compare results across research teams. For example, a large variety of enzymes from different sources such as of porcine, rabbit or human origin have been used, differing in their activity and characterization. Differences in pH, mineral type, ionic strength and digestion time, which alter enzyme activity and other phenomena, may also considerably alter results. Other parameters such as the presence of phospholipids, individual enzymes such as gastric lipase and digestive emulsifiers vs. their mixtures (e. g. pancreatin and bile salts), and the ratio of food bolus to digestive fluids, have also been discussed at length. In the present consensus paper, within the COST Infogest network, we propose a general standardised and practical static digestion method based on physiologically relevant conditions that can be applied for various endpoints, which may be amended to accommodate further specific requirements. A frameset of parameters including the oral, gastric and small intestinal digestion are outlined and their relevance discussed in relation to available in vivo data and enzymes. This consensus paper will give a detailed protocol and a line-by-line, guidance, recommendations and justifications but also limitation of the proposed model. This harmonised static, in vitro digestion method for food should aid the production of more comparable data in the future., COST actionEuropean Cooperation in Science and Technology (COST) [FA1005]; Biotechnology and Biological Sciences Research CouncilBiotechnology and Biological Sciences Research Council (BBSRC) [BBS/E/F/00044420], COST action FA1005 Infogest22 (http://www.cost-infogest.eu/) is acknowledged for providing funding for travel, meetings and conferences. The many other researchers, mostly associated to the above COST action, which have contributed to the discussion on digestion parameters are also acknowledged.

We have previously estimated the lytic ability of many lactococcal strains as well as their proteinase and global peptidase activities using buffer and pseudo-curd tests. In the present study, we have selected five lactococcal starters having different lytic and proteolytic properties to manufacture semi-hard cheeses. The lytic behaviour of the five strains in cheese correlated with their estimated lytic ability. Cell lysis positively influenced the ripening of cheese: proteolysis was more advanced in cheeses made with the three lytic strains. However, high cell lysis was not sufficient to obtain cheeses with good flavour scores and in particular non-bitter cheeses. The cheeses made with the strain Lactococcus lactis subsp. cremoris RD251, whose cells lysed highly during ripening but whose global peptidase potential was low, were bitter as were the cheeses made with the low lytic strain Lactococcus lactis subsp. lactis RD232 whose cells possessed a high proteolytic potential.

Background: The digestive hydrolysis of dietary proteins leads to the release of peptides in the intestinal tract, where they may exert a variety of functions, but their characterization and quantification are difficult. Objectives: We aimed to characterize and determine kinetics of the formation of peptides present in the jejunum of humans who ingested casein or whey proteins by using mass spectrometry and to look for and quantify bioactive peptides. Design: Subjects were equipped with a double-lumen nasogastric tube that migrated to the proximal jejunum. A sample collection was performed for 6 h after the ingestion of 30 g 15 N-labeled casein (n = 7) or whey proteins (WPs; n = 6). Nitrogen flow rates were measured, and peptides were identified by using mass spectrometry. Results: After casein ingestion, medium-size peptides (750‐1050 kDa) were released during 6 h, whereas larger peptides (1050‐1800 kDa) were released from WPs in the first 3 h. A total of 356 and 146 peptides were detected and sequenced in the jejunum after casein and WP ingestion, respectively. b-casein was the most important precursor of peptides, including bioactive peptides with various activities. The amounts of b-casomorphins (b-casein 57‐, 58‐, 59‐, and 60‐66) and b-casein 108‐113 released on the postprandial window were sufficient to elicit the biological action of these peptides (ie, opioid and antihypertensive, respectively). Conclusions: Clear evidence is shown of the presence of bioactive peptides in the jejunum of healthy humans fed casein. Our findings raise the question about the physiologic conditions under which these peptides can express their bioactivity in humans. This trial was registered at clinicaltrials.gov as NCT00862329. Am J Clin Nutr doi: 10.3945/ajcn.112.055202.

Infant formulas (IFs) are major sources of proteins for the neonate when breast-feeding is not possible. Heat treatments used during IF manufacture affect the structure of milk proteins but the impact of these structural modifications on the digestion of milk proteins and the identity of the bioactive peptides released in the gut have never been studied so far. The objective of this work was to determine the impact of two technological parameters (percentage of dry matter of the milk concentrate prior to heat treatment and intensity of the heat treatment applied to it) considered as essential in IF manufacture on the resistance of milk caseins (CNs) to digestion. Six skim milk powders were manufactured by spray-drying after having submitted 25% or 35% dry matter milk concentrates to three types of heat-treatment traditionally used in industry (80°C/20 s, 85°C/180 s, 105°C/60 s). Those six samples and a reference unheated one were characterised (particle size, composition…) and submitted to an in vitro digestion model mimicking the gastrointestinal digestion of an infant. Digested samples were characterised by SDSPAGE and western-blotting and by ELISA using a collection of 23 αs1, αs2, β and κ-CN-specific monoclonal antibodies. Kinetics of β-CN hydrolysis was studied by antibody arrays. Peptides resisting to digestion were identified using mass spectrometry. Heat-treatment of milk prior to spray-drying was shown to significantly increase the residual CNs immunoreactivity monitored after digestion. Areas showing either post-translational modifications or high hydrophobicities were identified as being the most resistant to digestion whatever the process studied was. Ke

International audience; Caseinphosphopeptides (CPPs) are phosphorylated fragments of caseins, which are found in dairy products. One of their unique features is their ability to bind calcium. There are several published methods to extract CPPs from cheese, but none allows their quantitative evaluation. A chromatographic procedure allowing a semi-quantitative evaluation of cheese CPPs was adapted from a previously published method and tested on Beaufort cheese. Water-soluble peptides were extracted from cheese and purified using cation-exchange chromatography followed by immobilised metal-ion affinity chromatography (IMAC). CPPs were identified using mass spectrometry (LC-ESI-MS/MS). Fifty-five peptides, including 48 CPPs carrying one to three phosphorylations, were identified in Beaufort cheese. It can thus be considered that the selectivity of the chromatographic procedure proposed is sufficient for a semi-quantification of CPPs with a molecular mass ranging from 600 to 10 000 g*mol−1 in cheese. As IMAC fractions contain molecules with a molecular mass

Caseinomacropeptide (CMP) is a peptide obtained from kappa-casein hydrolysis by gastric proteinases and which exhibits various biological activities. The aim of this study was to analyze the intestinal processing of CMP at the brush border membrane (BBM) level. Intestinal BBM vesicles (BBMV) were used to digest glycosylated and unglycosylated CMP. Our results demonstrated that whatever was the glycosylated state of CMP, they were digested by BBMV intestinal enzymes, from macropeptides to free amino acids. The digestion of unglycosylated and glycosylated CMP throughout the action of exopeptidases was similar, but the activity of endopeptideases on glycosylated CMP was limited, certainly due to the attached O-glycosylations. Consequently, much more peptides were identified from the unglycosylated than from the glycosylated CMP. In addition, the glycosylation core as well as the number of the attached glycosylated chain modified the kinetic of digestion; the most heavily glycosylated forms being the slowest digested.

Soft cheese ripening is mainly controlled by proteolytic activities of Geotrichum candidum and Penicillium camembertii. To investigate the proteolytic activities involved in the synergistic effect, pure and mixed cultures of both micro-organisms were performed on Camembert juice. Proteolysis monitored throughout culture using SDS–PAGE and RP-HPLC profiles, as well as free amino acids (FAAs) concentration time-courses showed that G. candidum degrades immediately large and medium peptides in FAAs, which were partly assimilated, while P. camembertii assimilated large peptides but medium and small peptides were less consumed. The similar chromatograms of the mixed and G. candidum cultures tend to demonstrate that the proteolytic activities of G. candidum dominated in the mixed culture up to 112 h. Continuous proteolysis and assimilation of peptides occurred throughout the second part of P. camembertii culture, leading to the production of FAAs. These activities allow G. candidum to have medium and small peptides to hydrolyse during the mixed culture. Because of the rapid degradation of these peptides in FAAs, no more peptides were available for P. camembertii growth, which should therefore assimilate FAAs, leading to a rapid decrease of their concentration. The synergistic effect between G. candidum and P. camembertii was therefore predominant during the second part of culture.

Geotrichum candidum and Penicillium camembertii were cultivated in pure and mixed cultures on Camembert juice. This juice extracted from curd at the demoulding contains the whole substrates available for growth of surface flora in situ. A synergistic effect of G. candidum on P. camembertii growth was clearly shown in mixed culture; the enzymatic activities of G. candidum (low molecular weight peptides hydrolysis) allowed an easier assimilation of peptides and amino acids as carbon sources by P. camembertii, no other carbon sources were needed, or used only at the end of culture for cell maintenance, as was the case for citrate. A lower number of amino acids were convenient carbon sources for P. camembertii compared to G. candidum, resulting in its assimilation of lactose, lactate and citrate during pure culture, while G. candidum assimilated lactate and citrate only at the end of culture for the energy supply for cell maintenance. Peptides and amino acids metabolic behaviour was shown to be the main factor accounting for medium alkalinization, since their assimilation as carbon sources (in addition to nitrogen sources) resulted in ammonium production, which was found to be closely related to proton transfer.

The wide genotypic and phenotypic diversity of Geotrichum candidum strains does not facilitate its classification as yeast or a yeast-like fungus that is still a matter of debate. Whatever its classification, G. candidum possesses many different metabolic pathways that are of particular interest to the dairy industry. G. candidum is of importance in the maturation of cheese, and much is known about its direct contribution to cheese ripening and flavour formation. Its diverse metabolic potential means that G. candidum can play an important role in the ripening of many soft and semi-hard cheeses and make a positive contribution to the development of taste and aroma. It may also influence the growth of other microorganisms, both valuable and detrimental. The significance of the presence of G. candidum in cheese depends on the particular type of production and on the presence of biotypes featuring specific types of metabolism. However, in situ metabolic pathways involved in cheese ripening and their regulations are mainly unknown. The information available provides a good understanding of the potential of G. candidum strains that are used in cheese manufacture, and permits a better choice of strain depending on the characteristics required. The biochemical activities of G. candidum and its application in the dairy industry are presented in this review.

The structure development of a soft cheese curd model has been studied in relationship to its rheological properties and its biochemical characteristics (pH, amount and partition of minerals, casein proteolysis) at different technical steps including cutting, drawing, three turns and demoulding. Scanning electron microscopy was used to observe structural changes during the drainage of a fat-free soft cheese. The micrographs provided visual evidence of changes in the casein matrix from casein particles aggregated in clusters to uniform strands observed at the demoulding. The initial increase of loss tangent and of the exponent of the power law between G′ and G′′ and frequency (that were maximal at the second turn) was related to the solubilization of micellar calcium phosphate, while intact caseins and large casein fragments accumulated in the curd. After the second turn, the strength, Youngs' and loss moduli of the curd increased greatly. The hydrolysis of αs1-casein into αs1-I-CN f(24–199) may facilitate the rearrangement of casein particles within the curd. The pH-induced solubilization of calcium phosphate continued throughout the manufacture process but was unexpectedly incomplete at the end of the drainage. Combination of electron microscopic observations with dynamic rheological measurements and chemical and biochemical assessments provided increased knowledge about the structure of soft cheese during drainage, an important but poorly understood cheese making stage.

We emphasise the role of the lactococcal cell envelope proteinase (lactocepin) on the proteolysis in a curd of soft cheese. During cheese manufacture, proteolysis occurred as soon as the renneting stage with the action of the chymosin, and the level of proteolysis intensified rapidly. The peptides, present within the whey collected throughout the drainage, were identified using tandem mass spectrometry. From the sixteen peptides identified at the first turn, we showed the early predominant action of the lactocepin type III. From the forty eight peptides identified at the end of the drainage, we demonstrated, in addition to the predominant action of lactocepin, other activities that could result from the action of lactococcal peptidases. In addition, this study of proteolysis confirmed that the action of proteinases on casein in solution differed from their action in situ: some sites cleaved in solution were not cleaved in cheese and vice versa.

Proteolysis was considered as a typical biochemical parameter which allows cheese ripening and maturity to be characterised. Owing to methods for peptide sequencing, identification of peptides from cheese has been established as an efficient means to determine which proteolytic enzymes are active within cheese, their specificity, and casein molecular structure accessibility via cleavage site identification. This review is an attempt to determine whether these peptides produced in cheese can give information on the structure of paracasein matrix through the action of the inherent proteolysis (added coagulant, milk endogenous proteinases (plasmin, cathepsin) and proteinases and peptidases of bacterial origin). Some answers will be given with special reference to Emmental cheese of which some data on peptide characterisation are presented here.

Cheese can be considered as a paracasein network including fat and aqueous phases. Changes in the composition of the aqueous phase reflect the enzymatic and physico-chemical phe- nomena that occur in cheese during ripening. For the first time, juice was expressed by pressing from Camembert cheese ripened up to 16 d and analysed in addition to the cheese to evaluate the extent of proteolysis together with the solubilisation of minerais. The amount of expressable juice decreased sharply during ripening, i.e. from 67 to 19 % of the total water content for cheeses ripened 0 and 16 d, respectively. In parallel, the levels of pH 4.6-soluble nitrogen and non-protein nitrogen increased in the whole Camembert cheese; the increase was higher in the juice. Simultaneously, the concentration of organic phosphate in the juice increased with concomitant decreases in the concentrations of cal- cium and inorganic phosphate. This last observation suggests that salt precipitates at the surface of the cheese. The expression and subsequent analysis of juice from Camembert cheeses is an appropriate method for following the sequential action of proteolytic enzymes and minerai transfer that occur dur- ing ripening. © InralElsevier, Paris. soft cheese / aqueous phase / proteolysis / mineral/ ripening

The variations of the autolytic and proteolytic potential of lactococci need to be taken into account because these variations probably influence the development of organoleptic properties during cheese ripening. To predict lytic capacity, proteolytic potential, and specificity of cell surface-associated proteinase, we developed simple tests that were applied to 26 industrial strains and a few reference strains of Lactococcus lactis . The tests allowed us to measure the autolytic capacity of lactococci in a buffer or in a pseudo curd under conditions that were close to those of cheese ripening and to evaluate global peptidase activity, proteinase activity, and specificity using casein or casein hydrolysate as a substrate. We confirmed the variability of the autolytic capacity of lactococci and classified the strains into three groups by low, moderate, or high lytic capacity according to their behavior in the buffer and in pseudo curd tests. Validation of the latter was obtained by the observation of similar lytic behavior in the two reference strains of Lactococcus lactis , AM2 and NCDO763, which were highly autolytic and poorly autolytic, respectively, both in our tests and in previously reported cheese experiments. The global activities of peptidases and proteinase varied from 1 to 6 among the strains. Most of the proteinases that were isolated from the highly proteolytic industrial strains hydrolyzed β -casein preferentially and, consequently, are more like the PI-type proteinase than the PIII-type. We used simple, rapid methods to test a large number of strains to predict their lytic behavior and proteolytic activity in cheese.

Milk proteins are of interest as they contain soluble (SP) and non-soluble (casein) fractions that behave differently during digestion. SP are rapidly evacuated from the stomach whereas gastric emptying of casein is delayed (Boirie et al. 1997). This difference that has been demonstrated in vitro or in vivo in animals and in humans induces differential appearance of derived peptides and amino acids in the blood and postprandial metabolic response. This study aims to assess in humans the intestinal digestion kinetics of both protein fractions. It has been performed on 16 in good health volunteers whose diets were standardized during 9 days. On the 9th day they ingested the meal composed among others of 30 g of either casein or SP. Ileal effluents were continuously collected every 30 min for 6 hours using a double lumen nasogastric tube that migrated to the jejunum. In order to verify whether casein and SP present differential digestion in jejunum, immunoreactive proteins were quantified and peptides were identified using proteomic tools (chromatography coupled on line with mass spectrometry). This study shows that i) immunoreactive proteins and peptides were present in a greater amount during the first hour of digestion for SP meal whereas a two-step digestion was observed for casein meal: a first one at 1.5-2.5 hours and a second one 4-5 hours after meal ingestion, ii) large protein fragments were present within the jejunum for both meals thus demonstrating that proteins digestion was incomplete in the jejunum, and iii) the peptides derived from casein were smaller than the ones from SP. The digestion of casein and soluble proteins differed in both the intestinal kinetics and the molecular weight of the peptides. These differences offer several applications in overweight and elderly people or in patients with wasting disorders

All dietary proteins are potential sources of bioactive peptides, with a large range of beneficial effects on health. However, although technical progress has allowed significant breakthroughs in the identification of peptides issued from in vivo protein digestion, some links in the chain between protein ingestion and the physiological effect of the derived peptides are still lacking. For instance, true quantification of the peptides at each step of the degradation would be useful to explore a potential activity at the gut level. For peptides having peripheral effects, the major uncertainty is on their ability to cross the gut epithelium and to present a sufficiently long half-life in the plasma to be able to trigger a physiologic response. Finally, clear clinical evidence supporting the health effects of food-derived bioactive peptides are still weak. This review article takes stock of current knowledge in this research field.

International audience; The casein micelle is a highly aggregated colloid consisting of phosphoproteins and minerals, in particular calcium and phosphate. Its properties are affected by physico-chemical changes which provide possibilities for the development of new casein aggregates (CAs) with novel functionalities. The aim of this study was to investigate the emulsifying and emulsion-stabilizing capacity of gradually demineralized CAs in model dairy emulsions. Tri sodium citrate (TSC) was used to remove calcium and inorganic phosphate from pure casein micelles in order to produce four suspensions of differently demineralized CAs. Two types of milkfat-in-suspension (30:70 v/v) emulsions were then prepared to study the emulsifying and emulsion-stabilizing capacity of these CAs separately. Casein micelles were progressively demineralized (from 24 to 81% calcium reduction) and dissociated with the increase in TSC concentration. Three distinct populations of particles (micelle-like aggregates, sodium caseinate-like aggregates and casein monomers) were present in every suspension in different proportions. The smaller CAs had better emulsifying capacity and similar surface activity according to interfacial studies. The state of aggregation of the CAs was thus the main factor that controlled their emulsifying capacity. However, the emulsions formed with these smaller aggregates were less stable against creaming and flocculation, but still resisted coalescence under our storage conditions (21 days at 50 °C). The properties of the interfacial casein layers did not depend on the aggregation state of the CAs used to form the emulsions. The differences in instability were attributed to the nature of the non-adsorbed CAs and storage conditions.