การผลิตไมโครแคปซูลแอนโทไซยานินจากรำข้าวเหนียวดำ โดยวิธีทำแห้งแบบพ่นฝอยและแช่เยือกแข็ง

Abstract

The objectives of this thesis were to study the effects of process condition of anthocyanin microcapsule production from black glutinous rice by spray and freeze drying on the properties and storage stability of the obtained microcapsules, and to compare the efficiency of both processes. The bran from black glutinous rice (BGR) cv Kum Doi Saket were used as a raw material for preparation of anthocyanin extracts. Various conditions (solvent, acid content, solid/ solvent ratio, temperature and time) for anthocyanin extraction from BGR bran were studied to find the best condition with the highest anthocyanin content. The result shows that the extraction with 70 % ethanol acidified by 1.0 N HCl, 1 : 20 solid/solvent ratio (w/v), 90 min and 30 °C was the condition provided the highest anthocyanin content (2817.04 ± 67.50 mg/100 g DM). Anthocyanin extracted from this condition was prepared to 5 °Brix anthocyanin solution which was a core material. The milled rice fraction from milling process was produced to maltodextrin (used as wall materials) with different dextrose equivalent (DE) at 10, 20 and 30 (MD-10, MD-20 and MD-30, respectively) using a heat stable alpha-amylase (Termamyl®). In the experiment of spray drying, the condition of spray drying was varied as three inlet air temperatures (140, 160 and 180 °C) and three wall materials (MD 10, MD-20 and MD-30). The result shows that interactions between inlet air temperature and DE value have significantly (P ≤ 0.05) influenced to moisture content, aW, color parameters, solubility, dispersibility, wettability, surface anthocyanin content, microencapsulation efficiency and DPPH radical scavenging activity. While process yield, bulk density, angle of repose, total anthocyanin content and antioxidant activity by reducing power assay have been significantly (P ≤ 0.05) influenced by main factors. Morphology analysis by SEM shows that the higher inlet air temperature caused the bigger and smoother microcapsules, and MD-20 provided the largest number of microcapsule with smooth surface. Spray drying of anthocyanin at 180 °C inlet air temperature with MD-20 was the best microencapsulation condition which provided microcapsule with the best properties in most analysis. For the production of microcapsule by freeze drying, the wall materials were varied as three DE (MD-10, MD-20 and MD-30). The results show that the best wall material for microencapsulation by freeze drying was MD-20 that gave the best properties in most analysis. Morphology analysis of freeze dried microcapsule by SEM shows that all samples had the similar microcapsule surface. Comparative study found that freeze drying was microencapsulation process suitable for thermal sensitive core material. Freeze dried microcapsules provided overall properties better than spray dried micro-capsules. However, spray drying can remove more moisture and produces microcapsules with lower aW. For the storage stability study of anthocyanin microcapsules, the increasing of storage temperature (4, 25 and 45 °C) accelerated anthocyanin degradation. The best storage temperature in this study was 4 °C, which gave the highest stability of both spray dried and freeze dried micro-capsules. Spray dried microcapsule produced by MD-10 and dried at 180 °C inlet air temperature shows the highest stability with the lowest degradation rate constant (0.0017 day-1) and the highest half-life (407.73 day). While freeze dried microcapsule produced by MD-10 had the lowest degradation rate constant (0.0034 day-1) and the highest half-life (203.87 day) which was the most stable for freeze dried microcapsule. In conclusion, production of anthocyanin microcapsule by spray drying retarded anthocyanin degradation during storage better than freeze drying.