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

The nitrate contents of some evaporated milks or dry skim milks are sometimes abnormally high. Industrial thermal processings increase the amount of nitrates like. After flash pasteurization the level is two fold higher, after pasteurization and sterilization, the level is four hold higher. After heating during 120 minutes at 90 degrees C of an 2% casein solution the level of the nitrates like increases from 14,7 to 30,8 mg/kg E.S., while, the reactivity of milk proteins to the biuret reagent is enhanced. The dialysis of milk powder containing 106 mg NO3-/kg E.S. shows that more than 95% of the nitrate are in free state. The level of bound nitrates is nearly four times higher in soluble proteins than in casein.

The presence of organochlorated pesticides in foods intended for animal and human consumption is on one hand a real fact and on the other hand, it is known that they could alter some enzymes activities and, consequently, modify, at a larger or lesser extent, the metabolic pathways where they are implicated. According to this, it seemed interesting to study the influence of one of such molecules, dieldrin, on nutrients utilization. The work was carried out on adult quails (Coturnix coturnix japonica) of both sexes; 20 ppm, were mixed in their diets, during a period of 48 days. Dieldrin does not affect food intake in both sexes, but produces a significant weight decrease in the males. Nutritive utilization of protein, judged by digestibility coefficient and nitrogen balance do not suffered any alterations. Furthermore, dieldrin does not affect carbohydrate utilization (nitrogen free extract) and raw fiber. On the contary, fat digestibility decreased in pesticide treated males and was not altered in females and this effect dependend upon the exposition time to the contaminant.

Numerous studies have shown that a limitation of dietary saturated fatty acids and cholesterol associated with an increase in linoleic acid consumption lowers high blood cholesterol level (a risk factor in the development of atherosclerosis). Besides the importance of dietary fatty acid composition in determining blood lipoprotein concentrations, it has been shown that increased intake of dietary linoleic acid influences arterial thrombosis tendency in rats and improves blood platelet function in man. Linoleic acid rich diets also loffer arterial blood pressure in salt loaded rats and in hypertensive men. Moreover, these diets improve heart function in rats as measured by coronary perfusion rate and ventricular work. These favourable effects of linoleic acid on various risk factors of cardiovascular diseases are observed at dietary levels which largely exceed the minimum amount required to prevent or cure the essential fatty acid deficiency syndrome. It is evident that the study of the physiological effects of linoleic acid goes beyond the scope of this syndrome. Essential fatty acids have structural functions as integral part of membrane phospholipids and dynamic functions as precursors of prostaglandins. On account of their structural function, the essential fatty acids influence the fluidity of biomembranes and the activity of membrane-bound enzymes and receptor systems. Certain physiological effects of dietary linoleic acid would be explained via this mechanism. Moreover linoleic acid is known to regulate the endogenous prostaglandin biosynthesis. Though incomplete, the knowledge gained fully justifies the application of preventive measures proposed by numerous expert committees for groups of populations with a high rate of atherosclerosis.

Sodium nitrite and two N-nitroso compounds, N-nitrosomethylurea (NMU) and N-nitrosomethylurethane (NMUT) have been investigated in the adult rat with regard to their in vivo effects on glucose tolerance and insulin response to glucose. Their effects have been compared to the diabetogenic action of streptozotocin (SZ). Glucose challenge (0.5 g/kg) in order to test insulin secretion in vivo gives the same result in the sodium nitrite-treated (25 mg/day during 2 months administered in drinking water) as in the control rats. In the NMU-treated (100 mg/kg i.p.) and in the NMUT-treated (100 mg/kg i.p.) glucose-induced insulin secretion tested 1 or 8 days after drug administration is severely decreased during the second test, especially in the NMUT-treated rats. Rats receiving STZ (35 mg/kg i.v.) exhibit sluggish insulin secretion as soon as the first test. Since in situ formation of nitrites and nitrosamines has been detected in human, one wonders about their role in the aetiology of human diabetes.

Helix aspersa, studied in Brittany, has not a complete uricolytic enzymatic chain. Allantoïnase and allantoïcase are absent, but, in vitro, uricase and urease are very active. A part from uric acid, Helix aspersa shows a high rate of urea and ammonia. The level of these substances is dependant on the age of the snail and on its physiological state.

The aim of the work presented here is to study the effect of different factors on the amount of "free" nitrite in meat products. Two kinds of factors are involved: --factors modifying the amount of "free" nitrite in the product; --factors modifying the amount of nitrite determined as "free". The former are mainly depending on the storage conditions of the products, for instance: low pH, light exposure, high temperature, increase the nitrite losses. The latter are depending on the analysis methodology. A strong physical treatment of the samples, a high temperature during extraction, a long time of extraction, the repetition of the extraction, increase the amount of nitrite determined as "free" by releasing a part of the bound fraction. So, it is very important, for the significance of results in "free" nitrite determination, to know very precisely storage and treatment conditions of the samples.

1 256 french meat products samples belonging to the most popular types: 435 saucissons cuits (course ground cooked sausage); 226 saucisses de Strasbourg and 165 saucisses de Francfort (both finely comminuted Frankfurter type sausages); 430 pâtés de Campagne (country-type meat loafs) were analysed. For each type of product contents in nitrite and nitrate are given respectively for products sent by meat plants, handicraft firms and consumers. The average values lie significantly under permitted levels, but many vary in a wide range, especially as far nitrate is concerned.

Meat is a complex medium in which nitrates and nitrites react by processes which are not well known. We do not know how to determine the quantities added, and estimating the residual doses depends on the analytic techniques studied. The analysis begins with extractions and purifications by various techniques described. A brief description is then given of 13 techniques for determining nitrites, 5 of which were applied successfully to meat products, and 18 techniques for determining nitrates, 12 of them suitable for meats. The references are given. The authors conclude by stressing the need for better knowledge of the effect of extraction and preparation techniques in order to give meaning to the results obtained.

Although genuine gastro-intestinal allergy is sought as the cause of chronic urticaria or repeated vaso-motor headaches, a non-allergic intolerance of one or more ingested substances, additives to foodstuffs (colourants and conserving agents) are likely to be implicated. Dietary histories from such patients often reveal heavy consumption of charcuterie. Oral provocation tests, performed using additives and placebo, can reproduce symptoms reliably. The substance most frequently incriminated is sodium nitrite (E 250): out of 76 tests, 4 were positive and 4 doubtful. In these cases complete avoidance of E 250 led to significant improvement or cure. We discuss various hypotheses on the harmful effects of sodium nitrite, such as denaturation of histamine-binding SH-group rich mucoproteins, direct toxicity on microvilli or inhibition of intestinal histaminase.