Static in vitro digestion model adapted to the general older adult population: an INFOGEST international consensus.

Understanding the mechanisms of food digestion is of paramount importance to determine the effect foods have on human health. Significant knowledge on the fate of food during digestion has been generated in healthy adults due to the development of physiologically-relevant in vitro digestion models. However, it appears that the performance of the oro-gastrointestinal tract is affected by ageing and that a model simulating the digestive conditions found in a younger adult (<65 years) is not relevant for an older adult (>65 years). The objectives of the present paper were: (1) to conduct an exhaustive literature search to find data on the physiological parameters of the older adult oro-gastrointestinal tract, (2) to define the parameters of an in vitro digestion model adapted to the older adult. International experts have discussed all the parameters during a dedicated workshop organized within the INFOGEST network. Data on food bolus properties collected in the older adult were gathered, including food particle size found in older adult boluses. In the stomach and small intestine, data suggest that significant physiological changes are observed between younger and older adults. In the latter, the rate of gastric emptying is slowed down, the pH of the stomach content is higher, the amount of secretions and thus the hydrolytic activities of gastric and intestinal digestive enzymes are reduced and the concentration of bile salts lower. The consensus in vitro digestion model of the older adult proposed here will allow significant progress to be made in understanding the fate of food in this specific population, facilitating the development of foods adapted to their nutritional needs. Nevertheless, better foundational data when available and further refinement of the parameters will be needed to implement the proposed model in the future.

Review: On-farm and processing factors affecting bovine carcass and meat quality.

This paper reviews the current state of knowledge on beef carcass and meat quality, with particular emphasis on on-farm and processing factors associated with its high and inconsistent variability. The diversity of livestock systems comes from the diversity of breeds (dairy or beef), ages and gender (bulls, steers, heifers, cull cows) used to produce either mainly beef or beef and milk. In addition, there are factors linked to farming practices (including diet, especially grazing) which significantly influence the sensory, nutritional, technological and extrinsic (such as image) quality attributes of meat. These can become factors of positive differentiation when controlled by the application and certification of technical specifications. Finally, preslaughter (such as stress), slaughter (such as the chilling and hanging method of carcasses) and postslaughter (such as ageing, packaging and cooking) conditions have a strong influence on the microbiological, sensory, technological and image quality attributes of beef. In this review, potential synergisms or antagonisms between the different quality attributes are highlighted. For example, finishing cattle on grass, compared to indoor fattening on a high concentrate diet, has the advantage of producing leaner meat with a higher proportion of omega-3 fatty acids while exhibiting superior oxidative stability, but with the consequence of a darker meat colour and lower productivity, as well as higher seasonality and land surface requirements. Moreover, the control of on-farm factors is often guided by productivity (growth rate, feed conversion ratio) and carcass quality attributes (weight, conformation and fatness). Genetic selection has often been oriented in this direction, without taking other quality attributes into account. Finally, the interactions between all these factors (and especially between on-farm and slaughter or processing factors) are not considered in the quality grading schemes in European countries. This means that positive efforts at farm level may be mitigated or even eliminated by poor slaughtering or processing conditions. All these considerations explain why between-animal variability in quality can be high, even when animals come from the same farming system. The ability to predict the sensory and nutritional properties of meat according to production factors has become a major objective of the supply chain.

Review: Quality of animal-source foods.

This article critically reviews the current state of knowledge on the quality of animal-source foods according to animal production and food processing conditions, including consumer expectations-behaviours and the effects of consumption of animal-source foods on human health. Quality has been defined through seven core attributes: safety, commercial, sensory, nutritional, technological, convenience, and image. Image covers ethical, cultural and environmental dimensions associated with the origin of the food and the way it is produced and processed. This framework enabled to highlight the priorities given to the different quality attributes. It also helped to identify potential antagonisms and synergies among quality attributes, between production and processing stages, and among stakeholders. Primacy is essentially given to commercial quality attributes, especially for standard commodity animal-source foods. This primacy has strongly influenced genetic selection and farming practices in all livestock commodity chains and enabled substantial quantitative gains, although at the expense of other quality traits. Focal issues are the destructuration of chicken muscle that compromises sensory, nutritional and image quality attributes, and the fate of males in the egg and dairy sectors, which have heavily specialised their animals. Quality can be gained but can also be lost throughout the farm-to-fork continuum. Our review highlights critical factors and periods throughout animal production and food processing routes, such as on-farm practices, notably animal feeding, preslaughter and slaughter phases, food processing techniques, and food formulation. It also reveals on-farm and processing factors that create antagonisms among quality attributes, such as the castration of male pigs, the substitution of marine-source feed by plant-based feed in fish, and the use of sodium nitrite in meat processing. These antagonisms require scientific data to identify trade-offs among quality attributes and/or solutions to help overcome these tensions. However, there are also food products that value synergies between quality attributes and between production and processing phases, particularly Geographical Indications, such as for cheese and dry-cured ham. Human epidemiological studies have found associations between consumption of animal-source foods and increased or decreased risk for chronic non-communicable diseases. These associations have informed public health recommendations. However, they have not yet considered animal production and food processing conditions. A concerted and collaborative effort is needed from scientists working in animal science, food process engineering, consumer science, human nutrition and epidemiology in order to address this research gap. Avenues for research and main options for policy action are discussed.

Deciphering the protein digestion of meat products for the elderly by in vitro food oral processing and gastric dynamic digestion, peptidome analysis and modeling.

The elderly population will increase sharply in the future, along with an emerging range of specific nutritional needs that include adapted food. We aimed to develop a workflow to study the fate of a food, objectify the bioavailability of nutrients in the case of the digestive physiology of the elderly, and model the fate of proteins in the stomach. Pork frankfurters were subjected to in vitro normal and deficient mastication and gastric digestion, mimicking adult and elderly food oral and digestive processing. Swallowable food boluses were characterized for granulometric and rheological properties. Biochemical analyses were conducted on the bolus and on the digesta. Macronutrients, label-free peptide quantification and identification were performed, and modeling was applied to protein digestion kinetics. After deficient mastication, the food bolus was harder with more large particles, lower free iron release and more protein oxidation. The amount of peptides released in the stomach progressively increased, but to a lower extent for the elderly digestive condition and irrespective of masticatory efficiency. 592 peptides were identified from 67 proteins. Different trajectories were observed for adult and elderly digestive conditions, and two groups of meat proteins were identified based on the rate of hydrolysis. Designing suitable foods requires in vitro tools to evaluate the possible benefit for the elderly. Besides the well-known notion of Food Oral Processing (FOP), our work broadens the concept by extending oral activity to digestion when working in a nutritional context. This new concept is named Food Oral and Digestive Processing, FODP.

Digestion study of proteins from cooked meat using an enzymatic microreactor.

A semi automatic flow procedure with photometric detection was developed for the study of meat protein digestion. This system comprised two independent flow pathways, gathered by two compartments. The gastric compartment was simulated by an ultrafiltration cell fitted with a 10 KDa cut off membrane and the intestinal compartment was simulated by a 1 KDa cut off dialysis membrane. The pathways were filled with solutions simulating digestive conditions. The proposed system was employed in digestion studies of whole protein extracts from raw and cooked (100°C) meat. A mathematical modelling for the determination of the digestive kinetic constants was established. The results show that meat cooking leads to an important decrease of protein digestibility by proteases of the digestive tract.

Use of meat fluorescence emission as a marker of oxidation promoted by cooking.

Accumulation of fluorescent pigments in cooked bovine meat (M. Longissimus thoracis) was studied in relationship with the heating parameters (time and temperature). Muscles were aged at 4°C for 11days under vacuum before cooking. Meat cooking was performed by applying jets of steam. Three different heating treatments were tested: two with constant surface temperatures of 65 and 96°C for 300s, and one with a continuously increasing surface temperature up to 207°C. After extraction in water/dichloromethane/ethanol, fluorescence pigments were distributed between the apolar phase (emission 420-440nm after excitation at 360nm) and the polar phase, where two emission peaks were seen (emission 410-430 and 515nm after excitation at 360nm). Fluorescence in the two phases was little affected by heating at the two constant temperatures while it increased exponentially after 1min of treatment, as the varying temperature reached 141°C. The maximum fluorescence increases, measured in the extreme conditions of cooking (207°C/300s), were of 5000% in the apolar phase and 1700% in the polar phase. Thiobarbituric acid reactive substances (TBARS) and protein carbonyls were measured in parallel. The correlations between these two parameters and the fluorescence emission demonstrated that the interaction between proteins and aldehyde products of lipid peroxidation was mainly involved in the production of fluorescent pigments in cooked meat.

Pig Longissimus lumborum proteome: Part I. Effects of genetic background, rearing environment and gender.

A 2×2×2 factorial experiment on Longissimus lumborum of 24 pigs found that rearing environment (indoors or outdoors), breed of sire (Duroc or Large White), and gender (female or castrated male) influenced 22, 10, and 88 proteins of the soluble fraction, respectively, containing 220 matched spots in total. Some proteins were influenced by more than one main effect. Outdoor rearing resulted in lower levels of enzymes of the glycolytic pathway suggesting a more oxidative metabolism. Breed of sire slightly altered the balance of enzymes of the glycolytic pathway. Gender had profound effects. In particular, different enzyme levels suggest a more lipid oriented energy metabolism, and a higher extractability of myofibrillar proteins suggest altered control of the contractile apparatus, in castrated males. Differences in extractability did not explain the profound gender effects. Glycogen content, ultimate pH, drip and thawing losses showed main or interactive effects of the three treatment factors.

Pig Longissimus lumborum proteome: Part II: Relationships between protein content and meat quality.

Gender, rearing environment and breed of sire influenced 50.5% of the matched protein spots of the soluble fraction and some meat quality traits [Kwasiborski, A., Sayd, T., Chambon, C., Santé-Lhoutellier, V., Rocha, D., & Terlouw, C. (2008). Muscle proteome in pigs: Part I: Effects of genetic background, rearing environment and gender. Meat Science]. Multiple regression analyses determined that 1 or 2 proteins explained between 24% and 85% of variability in Longissimus meat quality. Regression models differed between treatment groups, but relationships between proteins and meat quality traits seemed to be related to common underlying mechanisms. Thus, proteins retained in models for ultimate pH, lightness, drip, thawing and cooking loss were related to the glycolytic pathway, phosphate transfer, or fibre type composition. Another model for thawing loss retained proteins related to denaturation of myofibrils or lipid content. The models for redness involved proteins related to post-mortem oxidative activity. Thus, proteins correlated with meat quality traits were related to biochemical mechanisms known to be involved in meat quality. Relative contributions of these mechanisms may vary according to gender, sire breed or rearing environment.

Role of calpains in postmortem proteolysis in chicken muscle.

Tenderness is governed by postmortem biochemical processes, particularly proteolysis. In mammals, the calpain system is generally accepted as the main system involved in postmortem proteolysis. In poultry, the 2 calpains (mu and mu/m--a form only found in bird tissue) have greater calcium sensitivity. In this study, we quantified by zymography the changes in postmortem calpain system activity. The mu/m-calpain activity remained steady, whereas the mu-calpain activity had disappeared by 6 h after postmortem, showing an activation by calcium. Changes in the electrophoretic pattern of sarcoplasmic and myofibrillar proteins are observed in the first postmortem hours concomitantly to the decrease in mu-calpain activity. The 30-kDa protein, considered as a good marker of postmortem aging in cattle, appeared from 6 h and then steadily increased. In chicken muscle, the rapid maximum tenderness reached could be explained by a greater activation of the calpain system.

Comparison of proteolysis in native, heat-treated and aged proteins from turkey meat.

1. The present study compared the ability of native, heat-treated and aged turkey breast muscle proteins to undergo proteolysis by digestive tract proteases. 2. Domestic turkey toms were slaughtered under laboratory conditions. Breast muscles were excised immediately post mortem; one was placed under conditions to develop exudative meat by maintaining the muscle at 40 degrees C for at least 30 min and the other was refrigerated under commercial conditions. 3. Meat was collected and stored for 7 d at 4 degrees C. Breast samples removed at d 0 and d 7 were frozen and stored at -80 degrees C until used for determination of solubility, protein surface hydrophobicity and protein oxidation through carbonyl content. Measurements of pepsin and trypsin/chymotrypsin activities were performed in vitro on myofibrillar proteins. 4. Storage increased carbonyl content in control samples while the oxidation increase was not significant in heat-treated myofibrillar protein. Hydrophobicity was not affected by storage time or treatment or protein solubility. 5. Storage significantly increased trypsin + chymotrypsin activity only in the control group. The activities of pepsin and trypsin + chymotrypsin were negatively correlated with protein surface hydrophobicity.

Oral declines and mastication deficiencies cause alteration of food bolus properties.

In the elderly, masticatory function often presents failure in certain oral tasks due to impairment such as decline in muscular force, jaw or tongue motility, neuro-muscular coordination, tooth damage, malocclusion and saliva production. Great disparity is observed in the various and potentially cumulative oral declines that occur with ageing. Such difficulties may have an impact on food consumption and nutritional status. To obtain better understanding of the consequences of several oral deficiencies, a series of swallowable boluses were prepared in vitro with the AM2 masticator apparatus with normal and deficient programming. Physiological normal mastication (NM) was simulated using in vivo data from healthy subjects. Chewing deficiencies were reproduced by alteration of NM programming to perform different levels and combinations of force loss, lack of saliva and decrease in the motility of oral elements. Poultry meatballs were used as test-food. Particle size distribution in the food bolus was measured by sieving and rheological features (hardness, cohesiveness and elasticity) were assessed with a TPA test. Compared to the NM outcome, significant and gradual deterioration of the food bolus was observed and associated with alteration in force, saliva and motility. Combinations of several failures led to greater or cumulative deficiencies in swallowable bolus properties. For the elderly presenting a high prevalence of various oral injuries, tailoring textured food cannot be ignored as a solution for remedying deficiencies and favoring the formation of a safe-swallowable bolus, which is an essential vector of nutrients. Knowing the impacts of oral injuries on the food bolus is obviously a requisite for developing diet strategies, including nutritional items for specific populations.

Combined in vivo and in silico approaches for predicting the release of bioactive peptides from meat digestion.

We studied the kinetics of peptide release during the gastric digestion of meat proteins in vivo, in view to predicting the release of bioactive peptides further on in the digestive tract. Six mini pigs fitted with gastric cannulas received a meal with cooked beef as protein source. Digesta was collected at regular time intervals up to 5½â€¯h. The peptides generated by the gastric digestion of meat were identified and quantified using label-free LC MS, thereafter subjected to in silico digestion mimicking the action of intestinal enzymes. Three clusters of proteins presenting similar evolutions according to their dynamic hydrolysis were obtained. This study clearly improves the in silico prediction of the intestinal release of bioactive peptides by mapping meat protein degradation in the stomach in an in vivo model. Knowledge of the conformation of the peptides released in the stomach further improves this prediction.

Quantification of peptides released during in vitro digestion of cooked meat.

We aimed to identify and quantify the peptides generated during in vitro digestion of cooked meat by liquid chromatography coupled with high resolution mass spectrometer. A total of 940 non-redundant peptides in the gastric compartment and 989 non-redundant peptides in the intestinal compartment were quantified and identified. Among the 71 different proteins identified, 43 meat proteins were found in the two digestive compartments, 20 proteins were specific to the gastric compartment and 8 proteins to the intestinal compartment. In terms of estimation, the proteins involved in muscle contraction and structure were preferentially enzymatically hydrolyzed in the small intestine. The effect of cooking provided different but less clear patterns of digestion. To the best of our knowledge, this constitutes the highest number of peptides identified in beef meat digests and provides a comprehensive database for meat protein digestion associated with cooking conditions. Such quantitative and qualitative differences may have important nutritional consequences.

Digestion of cooked meat proteins is slightly affected by age as assessed using the dynamic gastrointestinal TIM model and mass spectrometry.

In humans, meat ensures the supply of proteins with high nutritional value and indispensable amino acids. The main goal of the present study was to compare the degradation of meat proteins in adult and elderly digestive conditions. Cooked meat was subjected to in vitro digestion in the dynamic multi-compartmental TIM (TNO gastroIntestinal Model) system. Digestibility and bioaccessibility were determined using nitrogen balance and digestion products were identified using mass spectrometry. The TIM model was adapted according to in vivo data to mimic the specific digestive conditions of elderly people. Meat protein digestibility and bioaccessibility were around 96 and 60% respectively and were not influenced by age (P > 0.05). As much as 800 peptides were identified in the duodenal and jejunal compartments issued from 50 meat proteins with a percentage of coverage varying from 13 to 69%. Six proteins, mainly from the cytosol, were differentially hydrolyzed under the adult and elderly digestive conditions. Pyruvate kinase was the only protein clearly showing a delay in its degradation under elderly digestive conditions. This study provides significant insights into the understanding of meat protein dynamic digestion. Such data will be helpful to design in vivo studies aiming to evaluate dietary strategies that can attenuate muscle mass loss and more generally maintain a better quality of life in the elderly population.

Application to proteomics to understand and modify meat quality.

The use of proteomics in the field of meat science has gained in robustness and accuracy. This is consistent with the genomic and bioinformatic tools. Its application to sensorial and technological meat quality traits is discussed as well as the emergence of sanitary and nutritional issue which will grow in a next future.

Muscle composition slightly affects in vitro digestion of aged and cooked meat: identification of associated proteomic markers.

Meat is an appropriate source of proteins and minerals for human nutrition. Technological treatments modify the physical-chemical properties of proteins, making them liable to decrease the nutritional potential of meat. To counteract this damage, antioxidants and chaperone proteins in muscle cells can prevent oxidation, restore the function of denatured proteins, and thus prevent aggregation. This study aimed to explore the impact of indoor vs outdoor-reared meat protein composition on digestion and to associate protein markers to in vitro digestion parameters. Indoor-reared meat tended to show less oxidation and denaturation than outdoor-reared meat and was characterised by an overexpression of contractile and chaperone proteins. Outdoor-reared meat showed amplification of antioxidant and detoxification metabolism defending against oxidised compounds. Impacts on digestion remained minor. Several protein markers of in vitro digestion parameters were found for aged and cooked meat, linked to the detoxification process and to muscle contraction.

PRKAG3 and CAST genetic polymorphisms and quality traits of dry-cured hams--III. Associations in Slovenian dry-cured ham Kraski prsut and their dependence on processing.

The aim of the present study, the third in a series of three papers, is to show the effects of PRKAG3 and CAST gene polymorphisms on the quality traits of the Slovenian dry-cured ham "Kraski prsut" and their interaction with ham producers. Significant interaction of polymorphisms with producer in the case of salt content, lipid oxidation (PRKAG3 Ile199Val), proteolysis index (CAST Arg249Lys) and pastiness (CAST Ser638Arg) indicated that genotype manifestation was reliant on the manufacturing practice. PRKAG3 Ile199Val polymorphism affected several physico-chemical, rheological and sensory traits. The Ile/Ile genotype yielded less salty and softer hams, indicating beneficial effects on dry-cured ham quality. The effect of CAST polymorphisms was less pronounced, although the observed associations with pastiness, proteolysis index and several free amino acid concentrations indicate its possible influence on proteolysis, with haplotype CAST 249Arg/638Ser being associated with a higher degree of proteolysis.

Higher drip loss is associated with protein oxidation.

The study aimed to investigate the mechanisms underlying drip loss in meat other than those related to post mortem energy metabolism. The study was carried out on M. longissimus thoracis assessing carcass and meat quality traits plus metabolic parameters and drip loss. Based on the data obtained, three drip loss groups were established: low, medium and high. Heat treatments were performed at 100°C for 30 min. Physicochemical protein modifications were assessed before and after cooking. IMF and L* were higher in the high drip loss group, whereas b* was higher in the medium drip loss group. Residual glycogen, glucose and glycolytic potential were higher in LT muscle from the high drip loss group. Before cooking, protein surface hydrophobicity and carbonyl levels were similar in the three groups. However, after cooking, carbonyl, oxidized actin and oxidized aggregates were higher in the high drip loss group, suggesting that protein oxidation may affect the water holding capacity of meat.

Effect of heat treatment on protein oxidation in pig meat.

We investigated the oxidative mechanisms and identified the target protein induced by heat treatment. The study was carried out on M. longissimus thoracis from Galia and Redone pigs. Post mortem metabolic parameters and drip loss were determined. Heat treatment was performed at 100 °C for 10 and 30 min. Physicochemical state of the protein, TBA-RS and Schiff bases were assessed. Protein aggregates were evaluated and the protein target of oxidation studied. Muscles from Galia had higher residual glycogen and drip loss. Heat treatment increased surface hydrophobicity, carbonyl, protein aggregate and Schiff bases and TBA-RS whatever the treatment time. Immunoblotting revealed oxidized myosin, oxidized actin and high molecular weight proteins after 30 min cooking. Oxidation products were significantly correlated with drip loss, suggesting a possible reduced ability of oxidized proteins to retain water. Moreover, residual glycogen was positively correlated with oxidized myosin, suggesting a possible role of glycogen as a glucose donor.

PRKAG3 and CAST genetic polymorphisms and quality traits of dry-cured hams--II. Associations in French dry-cured ham Jambon de Bayonne and their dependence on salt reduction.

This study aimed to evaluate the effects of PRKAG3 Ile199Val and CAST Arg249Lys and CAST Ser638Arg polymorphisms on the quality traits of the French dry-cured ham Jambon de Bayonne and their interaction with salt reduction. Significant (p<0.05) and suggestive associations (p<0.10) between the polymorphisms and several quality traits of dry-cured ham, mainly related to processing and textural properties, were found. PRKAG3 Ile/Val and CAST 249Lys/638Arg presented the highest scores for sensory and processing properties, whatever the salt content.