The selection of raw materials and the roasting process are important aspects that influence the manufacturing and production of high quality peanuts. Over-roasting or under-roasting can significantly affect the color, flavor, texture and shelf-life of the end product. Nowadays, optimization of the roasting process and quality control of peanuts can be easily achieved by differential scanning calorimetry (DSC).
Analyzing the Roasting Process of Peanuts
Peanuts were grated into fine powder and filled into medium pressure crucibles. The same amount of weight in water was added and the crucibles were sealed. Evaluation of DSC curves indicates that temperatures in the range of 149-163 °C for 5 to 8 minutes are required for optimum finishedproduct texture, flavor and color. The optimum temperature and time conditions were established by determining the effect oil-roasting has on the peanut’s levels of residual undenatured arachin and nonarachin protein fractions.
The DSC curves in Figure 1 show evaluations for blanched and roasted peanuts respectively. The heating curves of blanched peanuts exhibit a small starch gelatinization endotherm at 80°C. This indicates that some gelatinization has already occurred during blanching. However, the denaturation peaks for nonarachin and arachin at 98 and 113°C, respectively, suggesting that blanching has not resulted in any significant protein denaturation. In comparison, roasting would result in a smaller residual starch gelatinization peak, the absence of the non-arachin peak and a broadened arachin peak which is significantly reduced in size. This indicates that arachin is partially denatured, due to over-roasting at too high a temperature.
Differential scanning calorimetry is a fast and easy technique that can be used to establish criteria for the optimization of raw material selection and the roasting process of peanuts. The DSC 1 profiles provide valuable information on the temperature and time conditions required for optimum texture, flavor and color as well as determining the effect oil-roasting has on the undenatured nonarachin and arachin proteins of the peanut.
The DSC 1 is an extremely useful instrument for quality control, research and development and, ultimately, for satisfying consumer expectations.
For more information: Quality of Peanuts with Thermal Analysis
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