Historical perspective of the Maillard reaction in food science.

Maillard's paper of 1912 describing the reaction between amino acids and sugars is both innovative and visionary. It provides original and still-valuable data on the chemistry of a new reaction and foresees its involvement in many scientific and biological domains, even in human pathology. This paper was ignored by the scientific community until 1941.

The absorption and metabolism of modified amino acids in processed foods.

The chemical reactions involved in the modifications of amino acids in processed food proteins are described. They concern the Maillard reaction, reaction with polyphenols and tannins, formation of lysinoalanine during alkaline and heat treatments, formation of isopeptides, oxidation reaction of the sulfur amino acids, and isomerization of the L-amino acids into their D-form. Information on the digestion, absorption, and urinary excretion of the reaction products obtained by using conventional nutritional tests is given.

Short-term dietary conjugated linoleic acid supplementation does not enhance the recovery of immunodepleted dexamethasone-treated rats.

Background: Conjugated linoleic acid (CLA) has been reported to decrease fat deposition, and increase lean body mass. This has been broadly inferred to mean that CLA alters protein turnover. However, data to test the effects of CLA on protein turnover are lacking.

Development of a rapid and convenient method to purify mucins and determine their in vivo synthesis rate in rats.

The intestinal mucoprotein synthesis rate was measured in vivo for the first time. For this, a rapid, reproducible, and convenient method to purify mucoproteins from large numbers of intestinal samples at the same time was developed. The method takes advantage of both the high mucin resistance to protease activities due to their extensive glycosylations and the high mucin molecular size.

Nutritional and metabolic consequences of the early Maillard reaction of heat treated milk in the pig. Significance for man.

Background: During the processing of foods, the Maillard reaction may occur contributing to altering the nutritional value of proteins. In dairy products the formation of lactuloselysine reduces the availability of lysine but the effects on the other nutrients are not very well known.

Aim Of The Study: Determination of the consequences of a high level of lactuloselysine in milk on the bioavailability of skim milk nutrients and the kinetics of their appearance in the portal blood and of their urinary and faecal excretions and extrapolation to lower heat treatments and to man, using the pig model.

Free and protein-bound glutamine have identical splanchnic extraction in healthy human volunteers.

The objectives of the present study were to determine the splanchnic extraction of glutamine after ingestion of glutamine-rich protein ((15)N-labeled oat proteins) and to compare it with that of free glutamine and to determine de novo glutamine synthesis before and after glutamine consumption. Eight healthy adults were infused intravenously in the postabsorptive state with L-[1-(13)C]glutamine (3 micromol x kg(-1) x h(-1)) and L-[1-(13)C]lysine (1.5 micromol x kg(-1) x h(-1)) for 8 h.

Effect of glutamine supplementation of the diet on tissue protein synthesis rate of glucocorticoid-treated rats.

Although glutamine status in the critically ill patient can be improved by nutritional means, the most effective way of effecting such supplementation has received little attention. We evaluated two different ways of supplementing clinical nutrition products with glutamine, either with free glutamine or by providing a glutamine-rich protein source, in acute glucocorticoid-treated (intraperitoneal dexamethasone, 120 mg/kg) rats. During the recovery period, the animals received isonitrogenous and isoenergetic diets containing either casein, mixed whey proteins with or without glutamine, or carob protein plus essential amino acids.

Neither glutamine nor arginine supplementation of diets increase glutamine body stores in healthy growing rats.

The aim of the work was to resolve whether glutamine and arginine supplemented diets affect plasma and tissue (muscle, liver and intestinal mucosa) glutamine concentrations, as well as glutaminase and glutamine synthetase specific activities. The trial was performed in growing rats fed 10% protein diets for 3 weeks. Protein sources were: whey proteins (W); whey proteins+free glutamine (WG); whey proteins+arginine (WA); and casein+wheat protein hydrolysate+acid whey (39:39:22), as source containing protein-bound glutamine (CGW).

Role of glutamine on the de novo purine nucleotide synthesis in Caco-2 cells.

Background: The body's nucleotide pool derives from three potential sources: de novo synthesis, salvage of preformed-nucleosides/bases or the diet. The relative contributions of these pathways of assimilation are poorly understood in vivo. Dietary nucleotides have been suggested to have beneficial effects an the development and repair of the gastrointestinal tract.

Effects of diet-induced hyperthreoninemia. II). Tissue and extracellular amino acid levels in the brain.

Growing rats were fed graded levels of threonine (Thr, 0.4, 0.8, and 3.

Stearidonic acid, an inhibitor of the 5-lipoxygenase pathway. A comparison with timnodonic and dihomogammalinolenic acid.

Leukotrienes have been shown to play an important role as mediators in various disease processes, including asthma and inflammation; thus, their synthesis is tightly regulated. The major precursor of leukotrienes is arachidonic acid (20:4n-6). Fatty acids which are structurally similar to 20:4n-6, such as eicosatrienoic acid (20:3n-6; dihomogammalinolenic acid) and eicosapentaenoic acid (20:5n-3; timnodonic acid) have been found to inhibit leukotriene biosynthesis.

Effects of diet-induced hyperthreoninemia. I). Amino acid levels in the central nervous system and peripheral tissues.

Rats were fed four levels of threonine (Thr, 0.4, 0.6, 0.

Effects of 9, 12, 15-octadecatrien-6-ynoic acid on the metabolism of arachidonic acid in platelets and on platelet aggregation.

An acetylenic fatty acid: 9,12,15-octadecatrien-6-ynoic acid (dicranin) was extracted from Dicranum Scoparium and preincubated with platelets which were then stimulated by exogenous arachidonic acid (20:4 n-6). This molecule at 10(-4) M weakly inhibited the cyclooxygenase activity as assessed by measurement of 12-hydroxy-heptadecatrienoic acid (HHT) In contrast, the 12-hydroxy-eicosatetraenoic acid (12-HETE) synthesized by the 12-lipoxygenase was strongly increased by about 650%. The same effects were observed with 10(-5) M and with 10(-6) M of dicranin but to a lesser extent.

Effects of 9,12,15-octadecatrien-6-ynoic acid on the metabolism of arachidonic acid in platelets and on the platelet aggregation.

An acetylenic fatty acid: 9,12,15-octadecatrien-6-ynoic acid (dicranin), extracted from Dicranum Scoparium was preincubated with platelets stimulated by exogenous arachidonic acid (20:4 n-6). Dicranin (10(-4) M) weakly inhibited the cyclooxygenase activity as assessed by measurement of 12-hydroxy-heptadecatrienoic acid (HHT) In contrast, the 12-hydroxy-eicosatetraenoic acid (12-HETE) synthesized by the 12-lipoxygenase was strongly increased by about 650%. The same effects were observed with 10(-6) M of dicranin but to a lesser extent.

Maillard reaction products and lysinoalanine: urinary excretion and the effects on kidney function of preterm infants fed heat-processed milk formula.

Heat processing is essential for the preservation of milk-based infant formulas. Heating, however, induces a number of chemical changes during which lysine in the milk proteins reacts with reducing sugars to form Maillard reaction products (MRPs) and also reacts with the dehydroalanine resulting from cystine degradation to form lysinoalanine (LAL). Both products have been reported to induce histological changes in the straight portion of the proximal tubule in the rat kidney.

Improvement in the nutritional quality of bread.

To assess whether the dipeptide N-epsilon-(gamma-L-glutamyl)-L-lysine (glutamyl-lysine) can serve as a nutritional source of lysine, we compared the growth of mice fed (a) an amino acid diet in which lysine was replaced by six dietary levels of glutamyl-lysine; (b) wheat gluten diets fortified with lysine; (c) a wheat bread-based diet (10% protein) supplemented before feeding with lysine or glutamyl-lysine (0, 0.75, 1.50, 2.

Effects of foods rich in polyphenols on nitrogen excretion in rats.

The extent to which tea, cocoa and carob (foods rich in polyphenols) influence fecal nitrogen (N) excretion was investigated in rats. The studies took into account the methylxanthine contents of tea and cocoa as well as the poor digestibility of cocoa nitrogen. Balance measurements indicated that all three food sources significantly increased fecal nitrogen excretion relative to methylxanthine-matched control diets (p less than 0.

The effect of Maillard reaction products on zinc metabolism in the rat.

The effect of giving Maillard reaction products (MRP) on zinc metabolism was investigated in the rat. In Expt 1, MRP were prepared by incubating casein with either glucose or lactose under controlled reaction conditions, and were quantified as either 'early' or 'advanced' after estimation of lysine loss and lysine destruction respectively. In Expt 2, the effect of the purified early MRP fructose--lysine (FL) on Zn metabolism was studied.

Black currant seed oil feeding and fatty acids in liver lipid classes of guinea pigs.

Guinea pigs were fed one of three diets containing 10% black currant seed oil (a source of gamma-linolenic (18:3 n-6) and stearidonic (18:4 n-3) acids), walnut oil or lard for 40 days. The fatty acid composition of liver triglycerides, free fatty acids, cholesteryl esters, phosphatidylinositol, phosphatidylserine, cardiolipin, phosphatidylcholine and phosphatidylethanolamine were determined. Dietary n-3 fatty acids found esterified in liver lipids had been desaturated and elongated to longer chain analogues, notably docosapentaenoic acid (22:5 n-3) and docosahexaenoic acid (22:6 n-3).

Metabolic transit and toxicity of Maillard reaction products.

The feeding of Maillard reaction products (MRP) has been reported to lead to a variety of effects on metabolism which may be classed as "anti-nutritional" or "anti-physiological", depending on whether they are due to the loss of essential nutrients or to the presence of the MRP per se. This paper describes the sensitivity of essential nutrients in the "early" and "advanced" stages of the Maillard reaction, the metabolic transit of Amadori compounds, premelanoidins, melanoidins, hydroxymethyl-furfural, carboxymethyl-lysine, as well as the effects of MRP on pancreatic amylase and on urinary zinc excretion.

Lysinoalanine: absence of mutagenic response in the Salmonella/mammalian-microsome mutagenicity assay.

Lysinoalanine (N epsilon-(DL-2-amino-2-carboxyethyl)-L-lysine) was tested for mutagenicity in the Ames Salmonella/mammalian-microsome mutagenicity assay. No mutagenic response was detected at doses up to 5 mg/plate when samples were pre-incubated without S-9 mix, nor when they were pre-incubated with S-9 mix prepared from Aroclor 1254-induced rat liver or kidney. The results indicate that the stereoisomers of lysinoalanine likely to be present in the greatest proportions in processed foods are not mutagenic in the Ames assay.