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The study of the stability of anthocyanins in food colorant powder is important to predict the quality changes occurring as the food products are processed, to prevent and control the degradation of the anthocyanins. The objectives of this study were to identify anthocyanin components in natural food colorants obtained from black rice bran, and investigate their thermal stability at 60, 80, and 100°C, pH stability from 2.0 to 5.0 and also their correlation with visual color, L * , C * , and h°. Results showed that only six types of anthocyanins, cyanidin-3-O-glucoside, cyanidin-3-O-rutinoside, delphinidin, cyanidin, pelargonidin and malvidin were present in raw black rice bran (BRB) and black rice bran colorant powder (BCP). The thermal degradation of both the visual color and the anthocyanin content in the BCP followed a first-order kinetic reaction model. The temperature-dependent degradation was adequately fitted to the Arrhenius equation. In terms of the pH stability, increasing pH values resulted in lower activation energies (E a ) and higher half-life (t 1/2 ) values for both color parameters and individual anthocyanins when heating from 60 to 100°C. Moreover, the degradation rate constant (k) increased with increasing temperature and pH value. The degradation of cyanidin-3-O-glucoside and total anthocyanins showed a strong positive correlation with C * . The changes in visual color may be used as an on-line quality control indicator during thermal processing of food products containing rice bran colorants which have high anthocyanin content.

Resistant Starch (RS) is one of nature's most interesting bioactive compounds. There is a wide variety of starchy food plants in Thailand that are good sources of RS, but they have not been well studied. As such, this study was carried out to investigate the potential food source of RS. Twenty-two promising food plants were selected. The samples included (1) cereals comprised of five long grain rice of O. sativa L. and sweet corn, (2) six species of root and tuber crops, (3) green banana fruits (Musa sapientum L.) composed of ABB group, AAB group and AAA group at the first stage of ripening and (4) legume seeds included cowpea seeds (3 different cultivars), red bean, red kidney bean and mung bean. All food plants were determined for chemical compositions, resistant starch, non-resistant starch, total starch and amylose content. The study found that the starchy foods varied in their chemical compositions. The major composition of all foods was carbohydrate ranging between 58.19 (in black speck cow pea) and 87.21% (in cassava root), whilst the fat, ash and fiber were observed only in small quantities. The protein content was highest in legume seeds (20.78 to 27.22%). For the study on starch compositions, green bananas contained highest amount of resistant starch ranging between 35.14 and 45.87%, indicating that more than a half of total starch in banana RS content varying from 35.14 to 45.87%, whereas the RS content of legumes ranging from 2.33 to 10.63% and 1.16 to 4.85% in cereal grains. Most of the starchy food plants contained moderate to high level of amylose (11.45-34.85%), except the waxy rice (2.72%).