Les modifications chimiques des proteines alimentaires sont realisees dans le but d'ameliore ... more Les modifications chimiques des proteines alimentaires sont realisees dans le but d'ameliore leurs proprietes fonctionnelles. Elles sont egalement pratiquees pour des etudes fondamentales de relations structure/fonction des proteines. Les principales modifications chimiques des proteine alimentaires sont presentees ainsi que leurs incidences sur les proprietes fonctionnelles telles le proprietes emulsifiantes, moussantes, visqueuses, d'hydratation et de gelification.
L'incidence des modifications chimiques des proteines du lait par acylation et amidation a et... more L'incidence des modifications chimiques des proteines du lait par acylation et amidation a ete etudiee sur les proprietes fonctionnelles des caseines et plus particulierement sur leur aptitude a coaguler. Ainsi, cette etude a permis de mettre en evidence que l'acetylation et la succinylation des proteines du lait conduit a une augmentation de la charge nette negative des caseines a l'origine de modifications de la structure micellaire se traduisant par une solubilisation des caseines et des mineraux colloidaux. L'acylation des caseines micellaires provoque un retard dans la formation des gels obtenus par voie acide ou enzymatique. Ce retard semble etre correle a une charge nette elevee des caseines acylees qui diminue la reactivite des micelles au cours de ces processus de coagulation. L'amidation des proteines du lait provoque une diminution de l'aptitude a la coagulation par voie acide du lait. L'augmentation des forces de repulsion d'hydratation entre micelles pourrait aussi etre responsable de ce phenomene.
Journal of photochemistry and photobiology. B, Biology, Jan 30, 2015
The effect of the alternation of light/dark periods (AL) (16/8min light/dark cycles and a photosy... more The effect of the alternation of light/dark periods (AL) (16/8min light/dark cycles and a photosynthetic photon flux density (PPFD) of 50μmolphotonsm(-2)s(-1) for three days) to clarify the mechanisms involved in the clomazone tolerance of tobacco plantlets primed with AL was studied. Clomazone decreased PSII activity, the net photosynthetic rate (Pn), and the ascorbate and total polyphenol contents and increased H2O2 and starch grain accumulation and the number of the cells that underwent programmed cell death (PCD). The pretreatment with AL reduced the inhibitory effect of clomazone on the PSII activity and photosynthesis, as indicated by the decreases in the H2O2 and starch grain accumulation and the PCD levels, and increased the content of ascorbate and certain phenolic compounds, such as chlorogenic acid, neochlorogenic acid and rutin. The AL treatment could promote photorespiration via post-illumination burst (PIB) effects. This alternative photorespiratory electron pathway ma...
Depending on the position of the fruit in the tree, mango fruit may be exposed to high temperatur... more Depending on the position of the fruit in the tree, mango fruit may be exposed to high temperature and intense light conditions that may lead to metabolic and physiological disorders and affect yield and quality. The present study aimed to determine how mango fruit adapted its functioning in terms of fruit water relations, epicarp characteristics and the antioxidant defence system in peel, to environmental conditions. The effect of contrasted temperature and light conditions was evaluated under natural solar radiation and temperature by comparing well-exposed and shaded fruit at three stages of fruit development. The sun-exposed and shaded peels of the two sides of the well-exposed fruit were also compared. Depending on fruit position within the canopy and on the side of a well-exposed fruit, the temperature gradient over a day affected fruit characteristics such as transpiration, as revealed by the water potential gradient as a function of the treatments, and led to a significant decrease in water conductance for well-exposed fruits compared to fruits within the canopy. Changes in cuticle thickness according to fruit position were consistent with those of fruit water conductance. Osmotic potential was also affected by climatic environment and harvest stage. Environmental conditions that induced water stress and greater light exposure, like on the sunny side of well-exposed fruit, increased the hydrogen peroxide, malondialdehyde and total and reduced ascorbate contents, as well as SOD, APX and MDHAR activities, regardless of the maturity stage. The lowest values were measured in the peel of the shaded fruit, that of the shaded side of well-exposed fruit being intermediate. Mango fruits exposed to water-stress-induced conditions during growth adapt their functioning by reducing their transpiration. Moreover, oxidative stress was limited as a consequence of the increase in antioxidant content and enzyme activities. This adaptive response of mango fruit to its climatic environment during growth could affect postharvest behaviour and quality.
Les modifications chimiques des proteines alimentaires sont realisees dans le but d'ameliore ... more Les modifications chimiques des proteines alimentaires sont realisees dans le but d'ameliore leurs proprietes fonctionnelles. Elles sont egalement pratiquees pour des etudes fondamentales de relations structure/fonction des proteines. Les principales modifications chimiques des proteine alimentaires sont presentees ainsi que leurs incidences sur les proprietes fonctionnelles telles le proprietes emulsifiantes, moussantes, visqueuses, d'hydratation et de gelification.
L'incidence des modifications chimiques des proteines du lait par acylation et amidation a et... more L'incidence des modifications chimiques des proteines du lait par acylation et amidation a ete etudiee sur les proprietes fonctionnelles des caseines et plus particulierement sur leur aptitude a coaguler. Ainsi, cette etude a permis de mettre en evidence que l'acetylation et la succinylation des proteines du lait conduit a une augmentation de la charge nette negative des caseines a l'origine de modifications de la structure micellaire se traduisant par une solubilisation des caseines et des mineraux colloidaux. L'acylation des caseines micellaires provoque un retard dans la formation des gels obtenus par voie acide ou enzymatique. Ce retard semble etre correle a une charge nette elevee des caseines acylees qui diminue la reactivite des micelles au cours de ces processus de coagulation. L'amidation des proteines du lait provoque une diminution de l'aptitude a la coagulation par voie acide du lait. L'augmentation des forces de repulsion d'hydratation entre micelles pourrait aussi etre responsable de ce phenomene.
Journal of photochemistry and photobiology. B, Biology, Jan 30, 2015
The effect of the alternation of light/dark periods (AL) (16/8min light/dark cycles and a photosy... more The effect of the alternation of light/dark periods (AL) (16/8min light/dark cycles and a photosynthetic photon flux density (PPFD) of 50μmolphotonsm(-2)s(-1) for three days) to clarify the mechanisms involved in the clomazone tolerance of tobacco plantlets primed with AL was studied. Clomazone decreased PSII activity, the net photosynthetic rate (Pn), and the ascorbate and total polyphenol contents and increased H2O2 and starch grain accumulation and the number of the cells that underwent programmed cell death (PCD). The pretreatment with AL reduced the inhibitory effect of clomazone on the PSII activity and photosynthesis, as indicated by the decreases in the H2O2 and starch grain accumulation and the PCD levels, and increased the content of ascorbate and certain phenolic compounds, such as chlorogenic acid, neochlorogenic acid and rutin. The AL treatment could promote photorespiration via post-illumination burst (PIB) effects. This alternative photorespiratory electron pathway ma...
Depending on the position of the fruit in the tree, mango fruit may be exposed to high temperatur... more Depending on the position of the fruit in the tree, mango fruit may be exposed to high temperature and intense light conditions that may lead to metabolic and physiological disorders and affect yield and quality. The present study aimed to determine how mango fruit adapted its functioning in terms of fruit water relations, epicarp characteristics and the antioxidant defence system in peel, to environmental conditions. The effect of contrasted temperature and light conditions was evaluated under natural solar radiation and temperature by comparing well-exposed and shaded fruit at three stages of fruit development. The sun-exposed and shaded peels of the two sides of the well-exposed fruit were also compared. Depending on fruit position within the canopy and on the side of a well-exposed fruit, the temperature gradient over a day affected fruit characteristics such as transpiration, as revealed by the water potential gradient as a function of the treatments, and led to a significant decrease in water conductance for well-exposed fruits compared to fruits within the canopy. Changes in cuticle thickness according to fruit position were consistent with those of fruit water conductance. Osmotic potential was also affected by climatic environment and harvest stage. Environmental conditions that induced water stress and greater light exposure, like on the sunny side of well-exposed fruit, increased the hydrogen peroxide, malondialdehyde and total and reduced ascorbate contents, as well as SOD, APX and MDHAR activities, regardless of the maturity stage. The lowest values were measured in the peel of the shaded fruit, that of the shaded side of well-exposed fruit being intermediate. Mango fruits exposed to water-stress-induced conditions during growth adapt their functioning by reducing their transpiration. Moreover, oxidative stress was limited as a consequence of the increase in antioxidant content and enzyme activities. This adaptive response of mango fruit to its climatic environment during growth could affect postharvest behaviour and quality.
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