Purple rice (Oryza sativa L.) is popular for planting and consuming in North and Northeast Thailand. The important pigment on the purple rice grain is anthocyanin which has high antioxidant activity. This research studied the effect of applying a pulse electric field (PEF) technique on the extraction of the total anthocyanin content, and the antioxidant activity of purple rice. The extraction treatment was divided into two levels of PEF [low and high PEF]. The low PEF treatment condition used low pulse numbers (0, 100, 300, and 500) at three levels of electric field intensity (2, 3, and 4 kilovolts / centimetres (kV cm–1) in 1 Hz). The high treatment condition used an electric field intensity of 6 kV cm–1 in 1 Hz with the pulse numbers of 1,000, 3,000, 4,000, and 5,000. The results indicated that a sample extracted with low PEF showed low anthocyanin content but high % of DPPH inhibition. In contrast, a high level of anthocyanin content and low % of DPPH inhibition were found in the high PEF extraction treatment. The result demonstrated that PEF technology did not cause a chemical change to anthocyanin but affected antioxidant activity. This effect was due to high energy and temperature generated in the high PEF treatment. The PEF technique has a benefit in decreasing the time required for the extraction process and does not negatively affect the anthocyanin extracted. The appropriate PEF extraction condition for purple rice was obtained at 6 kV cm–1 with 3,000 pulses, which provided an acceptable total anthocyanin content (2.50 ± 0.09 mg l–1) and was consistent with a percent inhibition of DPPH (60.97 ± 0.64). The results of this study have implications for the ongoing development and use of food-based products.
The objective of this research is to develop a new product of bamboo shoots, which is a seasoned deep fried shredded bamboo shoot. The study was divided into three parts which were the assessment of pre-treatment process for seasoned deep fried bamboo shoot prior to frying, the frying conditions and the consumer acceptability of the seasoning and flavour of the final product. Three pre-treatment processes assessed were freezing, vacuum drying and freeze drying. Three frying temperature levels were 160, 170, and 180°C for 3 and 5 seconds. Two seasoning flavours, corn cheese and paprika, were chosen in this study for a consumer acceptance evaluation. The results showed that the appropriate pre-treatment and frying conditions were the vacuum drying at 60°C for 3 hours and frying at 180°C for 3 second. This condition provided the good characteristics of inflated light golden yellow of the product with a low moisture content of 3.40±1.08% wet basis (w.b.), crispness value of 7.58 N and colour value in L* a* b* term were 51.57±0.91, 6.44±0.19 and 21.96±1.09, respectively. The consumer acceptability of the product was evaluated by sensory test using 9-points hedonic scale, it was found that the overall acceptability on corn cheese and paprika flavours of the product were moderate to much with the score of 7.08±1.44 and 7.18±1.25, respectively. It can be concluded that the bamboo shoots processed in this way have the potential to be developed into a new product.
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