The present study aimed to evaluate the digestion rate and nutritional quality of pig muscle proteins in relation to different meat processes (aging, mincing, and cooking). Under our experimental conditions, aging and mincing had little impact on protein digestion. Heat treatments had different temperature-dependent effects on the meat protein digestion rate and degradation potential. At 70 °C, the proteins underwent denaturation that enhanced the speed of pepsin digestion by increasing enzyme accessibility to protein cleavage sites. Above 100 °C, oxidation-related protein aggregation slowed pepsin digestion but improved meat protein overall digestibility. The digestion parameters defined here open new insights on the dynamics governing the in vitro digestion of meat protein. However, the effect of cooking temperature on protein digestion observed in vitro needs to be confirmed in vivo.

Several cultivars of apples (Malus domestica) were chosen for their variable concentrations and compositions in phenolic compounds. Cubed samples (1 cm3) were subjected to osmotic dehydration, and the effect of temperature was studied at 45 and 60 degrees C. Water loss, sucrose impregnation, and the evolution of some natural components of the product were followed to quantify mass transfer. Ascorbic acid and polyphenols were quantified by HPLC for several osmotic dehydration times and regardless of the quantity of impregnated sugar. Changes in antioxidant components differed as a function of the nature of molecules. Their concentrations decreased in line with temperature, and few differences were observed between cultivars. Processing at a lower temperature (45 degrees C) caused a total loss in ascorbic acid but allowed the retention of between 74 and 85% of initial polyphenols, depending on the cultivar. Cultivars containing highly polymerized procyanidins (such as Guillevic) experienced less loss. Hydroxycinnamic acids and monomeric catechins displayed the most marked changes. Leaching with water into the soaking solution was the principal mechanism retained to explain these losses.

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A regular consumption of fresh or processed fruits can contribute to preventing cardiovascular diseases and cancer. Polyphenols, which are naturally present in fresh apples (Malus x domestica), are widely acknowledged as antioxidants. Cider apples contain high concentrations of polyphenols, but their composition differs markedly as a function of cultivar. Two of which were studied in this respect. The first cultivar was Marie Menard, which is highly concentrated in polyphenols and has a standard profile showing high levels of hydroxycinnamic acids and monomeric catechins, widely involved in oxidation reactions catalyzed by the polyphenol oxidase; the second one was Guillevic, which has an atypical phenolic profile for a cider apple, with highly polymerized procyanidins and no monomeric catechins, which thus induces a low sensitivity to enzymatic browning. Both cultivars were subjected to osmotic dehydration at two temperatures (45 and 60°C) or to convective air-drying, and a combination of the two processes was also tested. Phenolic compounds were quantified by high performance liquid chromatography for various processing times and regardless of the quantity of impregnated sugar. The results revealed different behaviors depending on the polyphenolic groups of compounds. Procyanidins were better preserved by the processes than hydroxycinnamic acids or monomeric catechins. Indeed, these latter groups of polyphenols were first of all involved in enzymatic browning but could also diffuse more easily as their molecular weight was lower. Polyphenol retention was also dependent on the process applied. Polyphenols were better retained by convective drying than by osmotic dehydration, and when soaking was applied as a pretreatment, polyphenol losses were limited during subsequent drying. Moreover, the level of sucrose impregnation could mask the astringency of procyanidins.

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