Maillard reaction in mild-based foods: nutritional consequences.

Chemical reactions occurring during industrial treatments or storage foods can lead to the formation of epsilon-deoxyketosyl compounds, the Amadori products. Food protein value can be adversely affected by these reactions, and in particular lysine, an essential amino acid having on its side chain a free amino group, can be converted to nonbioavailable N-substituted lysine or blocked lysine. by acid hydrolysis of epsilon-deoxyketosyl compounds, furosine is formed. In this paper furosine prepared from milk-based commercial products has been evaluated by use of a recently developed HPLC method using a microbore column and phosphate buffer as the mobile phase at controlled temperature. Furosine levels have been used, together with protein, total amino acids, and lysine content, as an estimate of protein quality of a few different products such as cooked-cream dessert, yogurt mousse, white chocolate, milk chocolate, milk chocolate with a soft nougat and caramel center, milk chocolate with a whipped white center, chocolate spread, part-skim milk tablets, milk-based dietetic meals, and baby foods. The protein content of the analyzed products ranged from 34.3 gxkg(-1) (milk nougat) to 188.4 g x kg(-1) (milk tablets). The Maillard reaction caused a loss in available lysine that varied from 2.5% (cooked cream) to 36.2% (condensed milk). The contribution to the lysine average daily requirement is heavily affected by this reaction and varied from 13% (milk tablets and soft nougat) to 61% (dietetic meal). Variable results were also obtained for the other essential amino acids.

Analysis of epsilon-N-2-furoylmethyl-L-lysine (furosine) in dried milk by capillary electrophoresis with controlled electroosmotic flow using N,N,N',N'-tetramethyl-1,3-butanediamine in the running electrolyte solution.

The electrophoresis of epsilon-N-2-furoylmethyl-L-lysine (furosine) was studied in an attempt to develop a method for the identification and quantitation of this compound in processed food. The effect of pH and composition of electrolyte solution on both the electrophoretic migration of furosine and the electroosmotic flow in a bare fused-silica capillary of 75 mu m internal diameter was investigated. We demonstrate that the addition, to the running electrolyte solution, of N,N,N',N'-tetramethyl-1,3-butanediamine (TMBD) at concentrations ranging from 20 to 80 mM improves peak efficiency and can be used to modulate the migration time of furosine by controlling the electroosmotic flow which is reversed from cathodic to anodic. In a sample of dried milk subjected to a long period of storage under controlled conditions, furosine could be efficiently and reproducibly separated and quantitated by employing as the running electrolyte 60 mM TMBD titrated to pH 2.5. Capillary electrophoresis is a promising technique for the rapid identification and quantitation of furosine in processed food.

Comparative study on microwave and conventional methods for protein hydrolysis in food.

A rapid microwave hydrolysis procedure was developed for amino acid determination in food. The hydrolysis was performed with 6M HCl in sealed vessels using a microwave digestion system.Bovine Serum Albumin was chosen as a model protein to compare its theoric amino acid sequence with the experimental results obtained after hydrolysis by both the traditional oven heating and the microwave methods. Furthermore the selected microwave methods were carried out on different food matrices (cheese and durum wheat) and the obtained data were compared with the traditional method results.This comparative study shows that the rapid microwave hydrolysis is as accurate and precise as the traditional hydrolysis for determining amino acids in food.