The relationship between amylose to amylopectin ratio and functional properties of maize starch blends (system I) and "model mixtures" (system II) made of waxy and high amylose maize starch were investigated using the Rapid Visco Analyser (RVA). A 4-5% difference in amylose content caused significant difference in RVA curves and their first derivatives. Based on the first derivative of the RVA curves four different parameters (Peak 2, Peak Time 2, Peak 3, Peak Time 3) were defined. Peak viscosity and parameters were negatively correlated with amylose content confirming that amylopectin is mainly responsible for water uptake. The final viscosity of starch was very high and decreased as amylopectin or amylose was added, indicating that this parameter is the most sensitive to interactions in starch. In system II amount and characteristics of amylopectin seemed to primarily determine the pasting properties. Traditional RVA curves and parameters proved to be feasible to detect the differences between gel properties of the two systems after cooling. First derivative viscograms and alternative parameters seemed to be suitable to demonstrate the importance of interactions between the starch components during gelatinization. Our results confirmed that the Rapid Visco Analyser is a sensitive rheological tool for evaluating effects of starch structure and chemical composition on functional properties providing valuable help for food technologists.
Resistant starches (RS) can be used in food industry to enhance the dietary fiber content of different cereal based products such as pasta and bread. The aim of present study was to develop and evaluate the physical and functional properties of starch-based products enriched with RS. The in vitro enzymatic digestibility, cooking properties, and viscometric characteristics (using rapid visco analyzer= RVA) of the pasta products were determined. The results showed that the addition of resistant starches (RS-s) influenced the quality of both the raw and cooked pastas. Enzymatic digestibility and five RVA parameters (peak viscosity, trough, breakdown, setback, and final viscosity) were significantly reduced (p<0.05) in pasta products with added RS. Cooking quality characteristics were unaffected by RS addition. The results also indicated that interactions between RSs and other flour components may influence the in vitro digestibility of pasta products. According to the sensory evaluation of products, RS-s did not alter the sensory properties of pastas. However, the type of flour had significant effect on the sensory preference.
Cereal Chem. 86(4):398-404Importance of β-glucan in human nutrition is mirrored in numerous approval applications registering β-glucan containing products as health beneficial products in accordance with forthcoming EU Health Claims Regulation. In comparison to other cereals, barley contains considerable amounts of β-glucan. Naked barley is of particular interest because it circumvents the costs and loss of beneficial substances related to dehusking. In this study, the potential of near-infrared spectroscopy as an accurate, fast and economic method of determination of β-glucan in naked barley was appraised. Four different near-infrared instruments were used to analyze 107 barley samples, in both whole grain and milled form. Importantly, both black and purple pericarp samples, which are of addi-tional nutritional interest due to high anthocyanin content, and waxy samples, which show an extraordinary high β-glucan content could be analyzed within the same calibration set as the normal samples. All tested dispersive near-infrared reflection instruments showed suitability for supervision of breeding experiments and β-glucan monitoring in food industries (R 2 > 0.78). Common, industrially used near-infrared transmission instruments also provided reasonable results, although only suitable for rough selection according to β-glucan levels. On the other hand, the Fourier transform near-infrared reflection instrument was able to perform analytical analyses (R 2 = 0.96-0.98).
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