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The effect of microwave roasting on protease inhibitor activity and soluble protein content and composition in cracked soybeans was investigated in relation to the duration of treatment. Soybeans of Hodgson var. were cracked to 1/6-1/8 of the size of whole bean, dehulled and were exposed to microwaves at a frequency of 2.450 MHz. Soluble protein content of hexane defatted samples were determined and PAGE, SDS-PAGE and densitometric analyses were used to determine the change of major soybean protein subunits as a function of roasting time. Residual protease inhibitor activities and isoinhibitor composition were also determined.Microwave treatment is an effective way for inactivation of protease inhibitor activity in cracked soybeans. Roasting for only two minutes reduced the trypsin inhibitor activity to 13.33% of the initial value. Both types of inhibitors, Kunitz (KTI) and Bowman-Birk (BBI) were responsible for residual inhibitor activity. The duration of microwave roasting had strong influence on soluble protein content and polypeptide composition. Microwave treated samples were characterized by dominant content of glycinin, and high stability of acidic (-A1,2,3-, -A5-) and basic (-B1,2,3,4-) glycinin subunits were established.

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Increasing the protein and antioxidant content of food products is a constant challenge amongst researchers. Dried pasta products are popular amongst all groups of society. The most important factor in pasta processing is the quality of the flour. Millet (Panicum miliaceum) flour has high nutritional value, enriching it with cricket (Gryllus bimaculatus) flour is good choice to increase the quality of protein composition and antioxidant properties of products. Flour mixtures of millet and insect flours (5% and 10%) were analysed after mixing and pasta processing. Addition of wheat gluten improved both texture and nutrition value of pasta products. Total polyphenol content, antioxidant capacity, total protein content, free and total amino acid composition were studied. Quality analysis of dried pasta products were carried out according to Hungarian standards. Data was analysed with Kruskal-Wallis test, Dunn's pair-wise post hoc test was used with Bonferroni correction. The correlation was determined by Spearman's rank. Addition of cricket flour modified the pH, acid value, moisture content, and colour of the samples, these changes lasted during storage. Enrichment could increase the total phenol content significantly even at the low level of 10%. Heat treatment during pasta processing had negative effect on the antioxidant capacity except at higher cricket flour contents. Cricket flour's high protein content proportionately increased millet flour's, thus pasta products'. Dried pasta products passed all quality norms. Enrichment of millet flour with cricket flour is favourable from both nutritional and quality aspects.

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The protein content, solubility and functional properties of a total protein concentrate prepared from the seeds of Ailanthus excelsa Roxb. were determined. The effects of pH and/or NaCl concentration on some of these functional properties were also investigated. The protein content of the seed protein concentrate was found to be 65.88%. The minimal protein solubility was observed at pH 4 and the maximum was at pH 12. Water- and oil-holding capacities of the seed protein concentrate were 2.77 g g −1 and 5.79 g g −1 , respectively. The emulsifying activity and emulsion stability, as well as foaming capacity and foam stability, were greatly affected by pH levels and salt concentrations. Lower values were observed at slightly acidic pH (pH 4.0) and high salt concentration. Total protein concentrate was highly viscous which depends on concentration and pH levels. The lowest gelation concentration of seed protein concentrate was found to be 14% and 8% when the proteins were dissolved in distilled water and 0.5 M or 1 M NaCl solution, respectively.

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Comparative study of composition and technological quality of amaranth

I. Gross chemical composition, amino acid and mineral content

Acta Alimentaria
Authors: S. Tömösközi, I. Baracskai, R. Schönlechner, E. Berghofer, and R. Läsztity

Eight groups of amaranth grain samples, belonging to the species Amaranthus cruentus and A. hypochondriacus , grown in Austria and Hungary were studied. Gross chemical composition, amino acid content and mineral composition of the whole grain were determined. The effect of heat treatment on amino acid content was also investigated. The range of concentration of main constituents of samples studied corresponded to the average data reported by other researchers. However, the relatively big difference between lowest (14.23%) and highest (17.40%) protein content suggests that genetic potential for increasing the protein content may be realized in breeding. Amino acid composition profile is generally closer to Leguminosae than to cereal grains except for sulphur containing amino acids being present in higher amount in amaranth than in legumes. The concentrations of minerals in seeds varied in a relatively wide range, and the micro-components, like Fe, Cu, Zn, were present in higher amount in amaranth seeds compared to the average values found in wheat. It was confirmed that heat treatment of amaranth grain (e.g. popping) might reduce the available lysine content. Contradictory data published in the literature may be explained by differences in initial sugar and moisture content of grain, which influence the rate of potential Maillard-reaction.

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Fourier transform near infrared spectroscopy (FT-NIR) has been developed for determining the fat and protein contents of hard, semi-hard and processed cheeses. Multivariate calibration models were carried out by partial least squares (PLS) regression. The diffuse reflection spectra of different type of lyophilized cheeses were measured by FT-NIR analyser in the 800–2500 nm spectral range. The calibration set of 62 samples were validated by leave-oneout cross-validation and by prediction set of 31 samples. The optimal result for fat content (root mean square error of cross-validation (RMSECV)=1.0; R2=99.1%, PLS factor= 6) was obtained when the spectra were preprocessed by first derivation (FD) combined with multiplicative scatter correction (MSC) and smoothing. The optimal result for protein content (RMSECV=1.4, R2=97.2%, PLS factor=6) was observed when the first derivation combined with straight line subtraction (SLS) and smoothing spectral preprocessing method was applied.

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The changes in the activity of enzyme polyphenol oxidase, the concentration of total soluble phenolic compounds and soluble protein content in different tobacco cultivars (Virginia and Burley) during cultivation, then in a combined curing model system were studied. The latter was a special combination of air-curing and flue-curing methods followed by a long fermentation period to optimize the treatment of tobacco plants used both as protein sources and starting materials in tobacco industry. The results suggest that a cultivation period of 13–14 weeks could be better for tobacco plants as protein sources, however, for starting materials for industrial use 16–17 weeks are optimal. It was found a four-week curing period could be the best for two tobacco cultivars (Virginia and Burley) in the case of using them both as protein sources and starting materials in tobacco industry.

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In the microflora of sunflower seeds stored in domestic stores the, Alternaria species dominate, while those of Penicillium, Trichoderma, Stemphylium and Absidia spp. are present in lower numbers. During model tests (cca 20% seed moisture content, 25 °C, 4 weeks storage) the Alternaria species were almost completely eliminated and on the seeds mainly Aspergillus species, characteristic of stores, propagated. The moulds significantly deteriorated the quality of the seed and that of the produced oil and meal (reproductive ability, germinating power, oil content, lipoxygenase enzyme activity, acid value, peroxide value, fatty acid composition, UV absorbance, colour, sensorial properties, as well as the protein content, amino acid composition, colour and the smell of the meal), but no aflatoxin production occurred. The findings offer a comprehensive picture on the multiple destructive effects of incorrect storage.

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The effect of heat induced changes on the immunoreactivity of a-lactalbumin (a-la) in whey was evaluated. Whey and acidified a-la solutions were heated for various times at temperatures between 60 and 100 °C. After heating, the samples were clarified and the protein content (by Bradford's method), the quantity of a-la (by FPLC method) and the immune response to an anti a-la probe were determined. The samples heated at 80 °C were characterized by the highest a-la immunoreactivity properties. Raising temperature up to 90 °C and 100 °C caused a marked decrease in a-la immunoreactivity. As was found by FPLC method in the samples heated at 60 and 65 °C, a-la content changes were not statistically significant. A gradual decrease in the content of a-la was observed with increased temperature and duration of heating.

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Pleurotus djamor from Yucatan State, Mexico was compared with a local variety of P. ostreatus , in terms of chemical composition and amino acid profile. No differences were found (P=0.55) in crude protein content of P. djamor and P. ostreatus (20.2±0.15 vs. 20.3±0.16 g/100 g DM., respectively). P. ostreatus had a lower fiber and fat content (P<0.05). No difference was found in ash content (P>0.05). P. ostreatus has a higher proportion (P<0.05) of valine, isoleucine, phenylalanine, aspartate and alanine while P. djamor had higher proportion (P<0.05) of proline and glutamate, no difference was found in the remaining amino acids. Both species had a high proportion of aspartate and glutamate. In general, the human amino acid requirements for adults are satisfied, however, leucine and lysine might become limiting. It was concluded that P. djamor can be included in human diet in similar fashion as P. ostreatus .

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The objective of the study was to determine the effect of grain preparation technology, extrusion cooking conditions, and triticale cultivars on physico-chemical properties of crisp bread. Triticale cultivars used in the experiments differed in protein content, starch content, amylolytic activity, and viscosimetric properties. The type of the twinscrew extruder used has an effect on starch degradation, phenolic contents, and antioxidant activity of the product, but a greater effect on those characteristics is found for grain scouring prior to extrusion. All factors had an effect on volatile compound amounts in crisp bread, but the direction and range of these changes were random in character. Results of this study show that triticale grain can be useful raw material for the production of flat bread.

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