Annales de la nutrition et de l'alimentation最新文献

Ethanolic extracts containing soluble sugars were prepared from four foods : cassava, peanut, coconut and papaye. Six-month-old rats were given by stomach tube 10 mM CaCl2 solution (+ 45Ca) containing a carbohydrate. Depending on the group, the carbohydrate was glucose or melibiose or raffinose at 200 mM concentration, or one ethanolic extract. Blood samples were taken at different times after the administration and plasma radioactivity was measured. Rats were sacrificed at 24 hours; femur radioactivity was used as a measure of calcium absorption. Extracts of cassava, peanut, and papaye were the more patent in promoting calcium absorption. Extracts of coconut were less effective. This physiological activity of the extracts was correlated with the nature of sugars, identified by paper chromatography. Cassava contained raffinose, peanut included fructose, raffinose and stachyose. Fructose was abundant in papaye but in little quantity in coconut. The present experiments or earlier works had showed that these sugars enhanced calcium utilization.

Encephalomacia is a vitamin E deficiency syndrome which affects the cerebellum of young chicks. The lesion includes degenerative alterations of cellular and fibrillar elements, apparently as the result of the ischaemia caused by thrombotic events in the microvascular system. A supply of linoleic acid, as fatty acid methyl esters prepared from safflower oil (Carthamus tinctorius), caused a high incidence of encephalomalacia. On the other hand, linseed oil esters, rich in alpha-linolenic acid, did not induce any symptoms and protected the chicks to a large extend against the development of signs produced by linoleic acid. Fatty acid esters of cod liver oil, rich in long-chain derivatives of alpha-linolenic acid, exerted a relatively weak protective effect. The analytical results show that a supply of alpha-linolenic acid led to an accumulation of eicosapentaenoic acid, 20:5 omega 3, and a reduced concentration of arachidonic acid in the phospholipds of liver and plasma. The results suggest that, under the conditions leading to encephalomalacia, the prostacyclin-thromboxane balance is shifted in direction of an excessive production of TXA2, causing thrombus formation in the capillaries of the cerebellum, alpha-linolenic acid, by modifying the PUFA profile, exerts a multiple action the main result of which appears to be an antithrombotic effect at the level of the microvascular system of the cerebellum.

In chalky Champagne, nitrogen balance is study to adjust availability to plant response. For this, it is necessary to know some parameters whose measurement is obtained progressively; plants exportation, nitrogen transformations in terms of transport processes in soil system, kinetic of mineralization of soil organic nitrogen, plants residus and agricultural waste waters. Lysimeters with rotation of Champagne (wheat, sugarbeet, potatoes...) are used to measure losses of nitrogen and follow transport of nitrates by mean of soil solution captors. Comparisons with field results, lysimeters results and laboratory experimentations are used to adjust an experimental model. Two examples show: 1) Nitrogen fertilizer requirement for wheat. 2) Possibility of maximum application for agricultural waste waters.

From essential results have been obtained since 1971 in collaborative studies with E.N.S.A.I.A. de Nancy, F.N.I.E. et I.N.R.A. d'Antibes. If you have a nitrates low level in carrots, with average lower than 250-300 mg/kg; its necessary to choose ground with poor amount of organic matter (about less than 2%). Otherwise the practice of a strong irrigation, 15 days before the harvest, can lower nitrate level in quantity.

It is accepted that polyunsaturated fatty acids (PUFA) and vitamin E are interrelated, but the nature of the relationship is still highly controversial. There is non unanimity of opinion with respect to methods for detecting moderate deficiencies in vitamin E. The methods vary depending on the species studied due to inter-species variations on the physiological consequences of PUFA and vitamin E consumption. Studies on man are rare, but have permitted to identify groups which are particularly sensitive to a disequilibrium in PUFA and vitamin E intake, notably as a function of age or nutritional state. The effectiveness of PUFA and vitamine E varies in pathological conditions. Recommended allowances values can only be temporary because of the limits of our knowledge. In man PUFA and vitamin E are of interest primarily for disease prevention and secondarily for therapy. Vitamin E acts both to limit the peroxydation of fats and an antitoxic substance. The concentrations of PUFA and vitamin E are different in blood and tissue, and vary from one tissue to another. Vitamin E is supplied by a number of food sources, but certain oils have the advantage of providing simultaneously vitamin E and PUFA in biologically adequate proportions for man.

The toxic action of nitrates and nitrites has often been summarized by methemoglobinemia and nitrosation of amines inducing carcinogenic effects; these two impacts are spectacular, but they hide varying more or less insidious actions recently studied and perceived. In the NO3/NO2 couple, it is accepted that especially nitrite ion lays down a toxicological problem, probably because of its particular chemical reactivity: nitrite ion, which is the base of nitrous acid HNO2 (pKa = 3.36) can react with many functional groups from dietary or endogenous origin; it is also a reducing agent, only oxidable by chemical oxidants or adequate enzyme systems; at the same time it is an oxidant for many reduced substrates. These different possibilities explain the chemical complexity of these compounds and almost their reactivity in biological various media with toxicological implications (modification of the redox state). In man, the presence of nitrates in the digestive tract may result in nitrite formation, because nitrate-reductase from bacterial or enterocyte origin; more particularly in stomach, nitrites are characterized by a great instability imputable to the low pH of gastric juice and to secreted factors which accelerate phenomena; at the same time, nitrates and nutrites exercise opposite effects on gastric secretion (volume, acidity, pepsin) and on gastric mucosal irrigation: while nitrates increase these different parameters, nitrites reduce secretory activity but correlations between secretion and irrigation show that nitrates induce a deep modification of hydric compartment whereas nitrites rather react through cellular anoxy. In intestine, nitrates and chiefly nitrites are very quickly absorbed by a passive mechanism and they are characterized by an extrahepatic cycle; nitrates and nitrites are also eliminated in large quantities by kidneys, and nitrates have a very high diuretic effect: these NO3- ions move Cl- ions, inducing a Na+ waste, a decrease in extracellular space and an alkalosis; this diuretic action of ionic origin is moreover increased by a rise in glomerular blood flow facilitating filtration; these compounds therefore present vasomotor effects, probably by an action on catecholamines whose metabolism is modified. Last, nitrates are suspected to be responsible for reproduction troubles, thyroid dysfunction, perturbances of vitamins availability and nutritional effects. Most of the impacts of nitrates and nitrites are now well known, but their cellular of molecular action is not clear, and as a result there is a suspicion in regard to these products very widely present in food.

Different methods for nitrites and nitrates determination are described. Each step is considered separately, extraction, purification, determination of nitrate. During the last step, we examine the different analytical possibilities. Expecting for electrochemical methods, especially polarography, give satisfaction, the retained methods is that used as reference method for nitrate determination in meat and meat based products: Norme Afnor V04 - 409 et 410.

Analytical methods for volatile nitrosamines in foods and beverages are described. The possibilities of loss and formation of these compounds are discussed for each analytical step. The validity of the gas chromatographic and high performance liquid chromatographic determinations is evaluated for each detector type.