Maillard reaction products (MRP) were obtained by refluxing solutions containing either arginine and xylose (AX) or histidine and glucose (HG). The solutions were tested either unfractionated or partly purified by dialysis through a Spectra/Por (R)-6 membrane with a molecular weight cutoff at 1OOO. The bacteria tested were both pathogenic and spoilage bacteria frequently found in food. The effects of the AX and HG added were assessed on the basis of the growth curves and the MIC (minimum inhibitory concentration) values recorded. The MIC values obtained show that the inhibitory effect of MRP is dependent on the type of MRP and type of bacteria used. As can be seen from the growth curves, the lag phase of the growth was prolonged with increased concentrations of MRP. The results of the dialysis show that the high molecular weight fraction (MI >1OOO) was more inhibitory than the low molecular weight fraction (MI

Three different methods to evaluate antioxidative effect using assay systems consisting of emulsified linoleic acid are described. Oxygen consumption was measured by a polarographic technique using hemin to accelerate the lipid oxidation. The formation of conjugated diene compounds during oxidation at 37° C was determined by spectrophotometric measurement of absorption at 234 nm. A sensitive gas chromatographic procedure was used for direct recording of the development of different volatile compounds by analyzing the headspace gas over the reaction medium. In the latter case denatured horseradish peroxidase was used as the catalyst. The advantages and limitations of the different methods are discussed.

Maillard reaction products (MRP) obtained by reaction o f glucose, fructose or xylose with arginine, cysteine, glutamic acid, histidine, lysine or valine were studied with regard to their antioxidative properties. Model systems consisting of emulgated linoleic acid were used to evaluate the antioxidative effect o f the MRP. The antioxidative effect was found to be strongly dependent on the choice o f reactants, especially the amino acid. While MRP from glutamic acid with glucose or fructose showed no antioxidative properties, potent antioxidative products were obtained from, for example, histidine or lysine with any of the three sugars, or from arginine with xylose only.the influence o f p H and o f the molar ratio o f amino acid t o sugar o n the antioxidative effect of the MRP formed. Neutral or slightly basic initial pH was found to favor the production o f antioxidative products. Furthermore, the antioxidative effect was found t o be more favored by a high histidine concentration than by a high glucose concentration.The reaction between histidine and glucose was studied with regard t o

The structural changes of potato starch granules, caused by hydroxy‐propylation, were studied using light microscopy. The starch samples used consisted of a native potato starch, hydroxypropyl potato starches with varying molar substitution (M. S.) and a hydroxypropyl and cross‐linked potato starch. The structural characteristics of the samples were evaluated by comparing the colour intensities of thin sections of samples stained with iodine and Schiff's reagent. The manner of loss of birefringence of samples in 5 M aqueous urea under polarized light was observed as well. The results obtained by three different methods were found to be similar to each other, suggesting that the central region of the potato starch granule is where hydroxy‐propylation mainly takes place or where hydroxypropyl groups are mainly distributed. The results can provide an explanation for the altered pasting properties of hydroxypropyl potato starches depending on their M. S.

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Purified catalase and peroxidase were denatured by heat, acid and urea. Denaturation resulted in up to 22-fold increase in nonenzymatic lipid oxidation activity concomitant with loss of enzymatic activity. It is proposed that the increased nonenzymatic activity is due to increased exposure of the heme group. Acid-splitting of the hemoproteins into apoprotein and heroin had the greatest influence on both of the catalytic activities and recombination reversed the effect. Urea-denatured hemoprotein possessed increased nonenzymatic activity due to increased exposure of the protein-bound heine, however, peroxidase increased less than catalase which is consistent with the fact that peroxidase is the more heat stable enzyme. Nonenzymatic activity of the heat denatured hemoproteins was maximum when catalase was treated at 90 C for 2 min and peroxidase at 100 to 125 C for 5 to 30 min.

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