การสกัดแอนโทไซยานินจากรำข้าวก่ำโดยใช้คลื่นเสียงความถี่สูงและการกักเก็บสารสกัดในไมโครแคปซูล

Abstract

Black glutinous rice bran contains many antioxidants. One of them is anthocyanin, which is gaining popularity and interest in many areas. Since free radicals occur within the body are the main cause of deterioration of the body, many companies have applied antioxidant in health food supplements. There are efforts to extract antioxidants for commercial use. Ultrasonic extraction is a new method for extracting antioxidants from rice bran with high yield and shorter extraction time. However, anthocyanins are limited in their color stability. Therefore, encapsulation techniques were used to help protect anthocyanin. The objectives of this thesis were to study the optimum conditions for anthocyanin extraction from black rice bran using ultrasound and reduces extraction time and to study the effect of encapsulating agents on anthocyanin microcapsules produced by spray drying method. Five solvents were studied: distilled water, 50% ethanol, 70% ethanol, 50% ethanol acidified with 1% (v/v) acetic acid, and 70% ethanol acidified with 1% (v/v) acetic acid were studied and found that the best solvent was 50% ethanol acidified with 1% (v/v) acetic acid. It was found that the extraction using 50% ethanol acidified with 1% acetic acid, controlling the ratio of solvent to solid, temperature and extraction time of 20: 1 (volume/weight), 30 °C, and 90 minutes, respectively, gave the highest amount of anthocyanin, total phenolics and DPPH radical scavenging activity. (4,710.38 mg C3G equivalent/g dry weight, 13,271.96 mg gallic acid equivalent/100g dry weight, 152.39 mg Trolox equivalent/100 g dry weight, respectively). The extracted solvent was used in the study of ultrasonic extraction. Four process parameters were studied by using the central composite design as follows: solvent to solid ratio (12.93 – 27.07 ml/g), extraction time (15.86 – 44.14 min), amplitude (23.79% – 66.21%) and pulse duration (2.17 – 7.83 s). It was found that the optimum conditions for the extraction of antioxidants from black rice bran were solvent to solid ratio of 22.91 mg/g, extraction time of 34.18 min, amplitude of 58.27% and pulse duration of 3 s that provided the highest responses including anthocyanin content 6,902.52 mg C3G equivalent/100 g dry weight, total phenolic content 20,453.85 mg gallic acid equivalent/100 g dry weight and DPPH radical scavenging activity 287.48 mg Trolox equivalent/100 g dry weight. In addition, the ultrasonic extraction process at optimal conditions provided anthocyanin content, total phenolic content and DPPH radical scavenging activity higher than the conventional extraction method (shaking) by 20.06%, 20.69% and 16.76%, respectively. This result suggests that ultrasound extraction is an effective method for the extraction of antioxidants from black rice bran and it could be good information for the development of nutraceuticals in the food and pharmaceutical industry. Effects of 8 encapsulating agents on quality of microcapsules were studied: maltodextrin (MD), maltodextrin-gelatin (MD–GE), maltodextrin-whey protein isolate (MD–WPI), maltodextrin-gum Arabic, (MD–GA), modified starch (Sodium starch octenyl succinate, Hi), modified starch-gelatin (Hi–GE), modified starch-whey protein isolate (Hi-WPI) and modified starch-gum Arabic (Hi-GA). MD, MD–GA and MD-GA were found to be the potential encapsulating agents due to the highest encapsulation efficiency, low moisture content and low aw value. Except for the WPI-added samples, all microcapsules showed high water solubility and dispersibility with the highest values in MD sample. From the morphological study using the scanning electron microscope, it can be seen that all microcapsules were hollow spherical, small, scattered, and not clumped together.