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Peptide-bound advanced glycation end-products (peptide-bound AGEs) can be formed when peptides are heated with reducing saccharides. Pyrraline is the one of most commonly studied AGEs in foods, but the relative importance of the precursor peptide structure is uncertain. In the present study, model systems were prepared by heating peptides with glucose from 60˝C to 220˝C for up to 65 min, and the amounts of peptide-bound pyrraline formed were monitored to evaluate the effect of the neighboring amino acids on the peptide-bound pyrraline formation. The physico-chemical properties were introduced to explore the quantitative structure-reactivity relationships between physicochemical properties and peptide bound formation. 3-DG content in dipeptide-glucose model system was higher than that in the corresponding tripeptide-glucose model systems. Dipeptides produced higher amounts of peptide-bound pyrraline than the corresponding tripeptides. The peptide-bound pyrraline and 3-DG production were influenced by the physico-chemical properties of the side chain of amino acids adjacent to Lys in the following order: Lys-Leu/glucose > Lys-Ile/glucose > Lys-Val/ glucose > Lys-Thr/glucose > Lys-Ser/glucose > Lys-Ala/ glucose > Lys-Gly/glucose; Lys-Leu-Gly/glucose > Lys-Ile-Gly/glucose > Lys-Val-Gly/glucose > Lys-Thr-Gly/glucose > Lys-Ser-Gly/glucose > Lys-Ala-Gly/glucose > Lys-Gly-Gly/glucose. For the side chain of amino acids adjacent to Lys in dipeptides, residue volume, polarizability, molecular volume and localized electrical effect were positively related to the yield of peptide bound pyrraline, while hydrophobicity and pK b were negatively related to the yield of peptide bound pyrraline. In terms of side chain of amino acid adjacent to Lys in tripeptides, a similar result was observed, except hydrophobicity was positively related to the yield of peptide bound pyrraline.

The effects of perforated film packages (PFP) with different oxygen partial pressures (5, 8 and 10 kPa) and a barrier package (BP) at 21 kPa of O 2 on the quality of fresh-cut cabbages were studied at 5 and 20• C. The microbial growth, appearance, flavor, ascorbic acid content and polyphenol oxidase activity were determined during storage. The results indicated that fresh-cut cabbages had better color retention and quality in PFP. Oxidation of ascorbic acid (AA) and browning of fresh-cut cabbage were inhibited effectively using a PFP and an initial oxygen partial pressure equal to 5 kPa. Analysis of microbial growth also showed that the total count on fresh-cut cabbage was relative lower in PFP with an initial low O 2 content. Loss of total ascorbic acid was much lower in PFP than that in BP by suppressing AA oxidation. The results of sensory evaluation showed that flavor and appearance were maintained effectively at 5• C and significant differences in flavor were found between PFP and BP both at 5 and 20• C, while significant differences in appearance were found between PFP and BP only at 20• C.

Pyrraline, an advanced glycation end product (AGE), is related to some chronic diseases and can be employed as an indicator for heat damage in food processing. In this study, the impact of changing the reactant concentration and ratio on the kinetic parameters describing peptide-bound pyrraline (pep-pyr) formation and elimination was evaluated in the Lys-Gly/glucose model systems, with microwave heating treatment ranging from 120 to 200 °C. The maximum pep-pyr concentration increased as follows: 200 °C ˂ 180 °C ˂ 160 °C ˂ 120 °C ˂ 140 °C. First, the pep-pyr formation and elimination was modeled by using a single-response modelling. The formation rate constant (k ) of pep-pyr was independent of the initial concentration of the reactants and ratios. However, the elimination rate constant of pep-pyr (k ) increased with increasing reactant concentrations. Second, a multiresponse modelling was performed to illustrate the pathways of pep-pyr formation and elimination. Two adapted models can fit to the experimental data with the goodness-of-fit ranging from 0.663 to 0.920. Glucose-to-fructose isomerization rather than glucose-to-mannose epimerization was detected in an equimolar model system and the model system with an excess of any of the reactants. The caramelization reaction was negligible in the equimolar systems and the model systems with an excess of peptide. The reaction rate constant of glucose-to-fructose isomerization was independent of the initial reactant ratios. It was more difficult for pep-pyr elimination in the model system with an excess of peptide than that in the other 2 model systems (the equimolar system and the system with an excess of glucose), whereas a reverse result in pep-pyr formation was obtained.

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