No abstract

Maillard products arise from condensation reactions between amino acids or proteins with reducing sugars during food processing. As ubiquitous components of human food, these early or advanced glycation products may be subject to intestinal absorption. The present study was performed to investigate the intestinal uptake of Maillard products and to determine whether they are substrates for peptide and amino acid transporters expressed at the apical membrane of Caco-2 cells. At a concentration of 10 mM, H]leucine by more than 15 %. We also studied the transepithelial flux of Maillard products across Caco-2 cell monolayers cultured on permeable filters. The flux rates of Maillard products ranged from 0·01 to 0·3 %/cm 2 per h and were shown to be much lower than those of carrier substrates such as glycylsarcosine, L-proline and the space marker [ 14 C]mannitol. We conclude that the Maillard products investigated in the present study are neither transported by PEPT1 nor by carriers for neutral amino acids. The low transepithelial flux measured for these compounds most probably occurs by simple diffusion.

Forty-four boneless, cured hams were assigned to treatment groups to study the effect of tumbling, tumbling time (18 hr intermittent, 9.5 hr intermittent, 3 hr continuous), tumbling temperature (5°C and lS"C), sodium tripolyphosphate (TPP) pickle level (0 and 3.3%), and trim (lean, regular, and fat) on the quality and yield of canned hams. Tumbling significantly improved ham external appearance, color, sliceability, taste and aroma, and yield. Three-hour continuous tumbling resulted in less improvement in product quality and yield than did the 18-hr intermittent tumbling. Significant improvements in external appearance, color, sliceability, taste and aroma, and yield resulted from TPP treatments. Hams trimmed to 3 mm fat cover or less before tumbling had significantly better sliceability and yield.

Although the Maillard reaction between proteins and carbohydrates is of central importance for food processing and in vivo processes, only little is known about changes of the metal-binding properties induced by protein glycation. The purpose of this study was to examine the complex formation of the quantitatively important peptide-bound Maillard reaction products (MRPs) N(epsilon)-fructoselysine and N(epsilon)-carboxymethyllysine with the biologically relevant metal ions copper(II) and zinc(II). The MRPs were synthesized as the N(alpha)-hippuryllysine derivatives in order to block the coordination function of the alpha-amino group. Stability constant measurements were performed in aqueous solution using pH potentiometry. N(alpha)-Hippuryl-N(epsilon)-fructoselysine forms moderate Cu(II) complexes (Log(10) K(1) = 5.8; Log(10) K(2) = 4.0) but fails to form any complexes with Zn(II). N(alpha)-Hippuryl-N(epsilon)-carboxymethyllysine gives slightly stronger complexes with Cu(II) (Log(10) K(1) = 7.3; Log(10) K(2) = 6.3), but again no complexation with Zn(II) was observed. These results show that post-translational modification of proteins by carbohydrates leads to the formation of new coordination centers for metal ions within a protein chain. Further studies are necessary to clarify the consequences of this phenomenon in terms of protein quality and physiological processes.

The reaction of the Nalpha-hippuryllysine (BzGK) with fructose was investigated in two model systems to obtain an insight in fructose-induced modification of lysine in bakery products. After BzGK and fructose had been heated in a buffered low-moisture model system (80 degrees C, 60 min, aW = 0.86, pH 7.4), formation of epimeric Heyns compounds Nalpha-hippuryl-Nepsilon-glucosyl-lysine (BzGGlcK) and Nalpha-hippuryl-Nepsilon-mannosyl-lysine (BzGManK) was clearly demonstrated using RP-HPLC with UV as well as MS detection. The Amadori compound Nalpha-hippuryl-Nepsilon-fructosyl-lysine (BzGFruK) was formed in glucose-containing samples. When BzGK was added to the dough of fructose-containing biscuits, the Heyns compounds were detectable after baking at 175 degrees C for 7 min. The yields of the Heyns compounds in the fructose-containing biscuits and the yield of the Amadori compound in the glucose-containing biscuits were determined to 33 and 63%, pointing to the fact that formation of substantial amounts of Heyns products is very likely in fructose-containing bakery products.