Thunnop Laokuldilok

Protease Treatment for the Stabilization of Rice Bran: Effects on Lipase Activity, Antioxidants, and Lipid Stability

ABSTRACT Rice bran lipid is rapidly made rancid by endogenous lipase enzymes. To inactivate rice bran lipase, an enzymatic hydrolytic method was developed and then compared with the thermal method. The efficiency of five proteolytic enzymes including trypsin, chymotrypsin, papain, bromelain, and Flavourzyme enzyme to stabilize rice bran was investigated. Moreover, the antioxidant content and storage stability of enzymatically stabilized rice bran (ESRB), thermally stabilized rice bran (TSRB), and raw rice bran (RRB) were studied. Trypsin, chymotrypsin, and papain showed a higher rate of hydrolysis than bromelain and Flavourzyme enzyme. After 120 min of hydrolysis, rice bran hydrolyzed by trypsin, chymotrypsin, and papain inactivated 80, 86, and 79% of lipase activity, respectively, whereas lipase activity of rice bran hydrolyzed by bromelain and Flavourzyme enzyme was higher than the initial rice bran. With a similar lipase inactivation level, the cheaper papain was used to produce ESRB. Total phenolics c...

Effect of Milling on the Color, Nutritional Properties, and Antioxidant Contents of Glutinous Black Rice

ABSTRACT Dehulled glutinous black rice (cv. Kam Doi Saket) was abrasively milled (0–60 s) to make a degree of milling (DOM) curve. The curve showed a nonlinear relationship between milling time and DOM. The slope sharply increased in the first 20 s; after this point, the increase was moderate. The redness of grain and flour surprisingly increased after milling, and the highest value was found at 20 s of milling. Protein, fat, and crude fiber were not uniformly distributed in the dehulled rice kernel. The rice retained only 76.95, 32.79, 20.24, and 36.57% of protein, fat, crude fiber, and ash, respectively, after milling for 60 s. Anthocyanins, γ-oryzanol, and α-tocopherol decreased by 74.49, 55.35, and 70.36%, respectively, after 10 s of milling. The scavenging activity decreased sharply when milling was carried out for longer than 30 s. The methanolic extract from rice milled for 60 s showed the lowest activity, which was 21.1 times lower than that of the dehulled rice extract. It was concluded that mill...

Effects of Spray-drying Temperatures on Powder Properties and Antioxidant Activities of Encapsulated Anthocyanins from Black Glutinous Rice Bran

The objective of this study was to determine the effects of spray drying temperature on the powder properties and antioxidant activities of encapsulated black glutinous rice (BGR) bran anthocyanins. The anthocyanins in BGR bran was extracted using acidified ethanol. The extract was encapsulated with malto - dextrin (DE10) using spray drying at various inlet air temperatures (IAT; 140, 160 and 180°C). The results revealed that increasing IAT enhanced productivity with lower energy consumption, encapsulation efficiency, solubility, disper- sibility, wettability, flowability and surface smoothness of the microcapsules. In contrast, total anthocyanin content (TAC), bulk density and color values (a*, C* and h°, respectively) of the microcapsules were decreased by increasing the IAT. Reducing power and DPPH radical scavenging activity of anthocyanin powders were not significantly different. In addition, anthocyanin powder produced using 180°C IAT showed the greatest encapsulation efficiency (96.72 ± 0.61%), solubility (87.42 ± 1.26%), dispersibility (86.45 ± 0.93%) and repose angle (23.50 ± 0.61 degree).

Deacetylation of Chitin and the Properties of Chitosan Films with Various Deacetylation Degrees

The degree of deacetylation is the proportion of glucosamine monomer residues in chitin. It affects many properties of chitosan. The objectives of this research were to study the deacetylation of chitin by alkaline and to investigate chitosan film properties with different degrees of deacetylation. Chitin was deacetylated by boiling (95°C) in concentrated sodium hydroxide (50%) solution for 120-300 minutes. The degree of deacetylation of chitosan was determined by potentiometric titration method. Chitin possessed a degree of deacetylation of 7.74%. The alkaline deacetylation produced chitosan with a degree of deacetyl- ation of 15.24-70.19%. We found a linear relationship between the degree of deacetylation and deacetylation time (degree of deacetylation = 2.476 + 0.230t, R 2 = 0.915). The deacetylation time had no effect on the yield and whiteness of the obtained chitosans. Film was formed from the obtained chitosan at each deacetylation time and their properties investigated. Increasing the deacetylation time increased the tensile strength, elongation and water vapor transmission rate of the films. In contrast, redness (a*) and yellowness (b*) of the films decreased.

Optimization of simultaneously enzymatic fructo- and inulo-oligosaccharide production using co-substrates of sucrose and inulin from Jerusalem artichoke

ABSTRACT Prebiotic substances are extracted from various plant materials or enzymatic hydrolysis of different substrates. The production of fructo-oligosaccharide (FOS) and inulo-oligosaccharide (IOS) was performed by applying two substrates, sucrose and inulin; oligosaccharide yields were maximized using central composite design to evaluate the parameters influencing oligosaccharide production. Inulin from Jerusalem artichoke (5–15% w/v), sucrose (50–70% w/v), and inulinase from Aspergillus niger (2–7 U/g) were used as variable parameters for optimization. Based on our results, the application of sucrose and inulin as co-substrates for oligosaccharide production through inulinase hydrolysis and synthesis is viable in comparative to a method using a single substrate. Maximum yields (674.82 mg/g substrate) were obtained with 5.95% of inulin, 59.87% of sucrose, and 5.68 U/g of inulinase, with an incubation period of 9 hr. The use of sucrose and inulin as co-substrates in the reaction simultaneously produced FOS and IOS from sucrose and inulin. Total conversion yield was approximately 67%. Our results support the high value-added production of oligosaccharides using Jerusalem artichoke, which is generally used as a substrate in prebiotics and/or bioethanol production.

Optimization of the Production Conditions of Glutinous Rice Bran Protein Hydrolysate with Antioxidative Properties

Glutinous rice bran (GRB) is a byproduct of milling rice. Because of its high protein content, GRB can be used to produce protein hydrolysate with antioxidative properties. The antioxidant activity of protein hydrolysate depends on hydrolysis conditions. In this study, protein from GRB cv. RD6 was prepared and then subjected to proteolytic hydrolysis by alcalase. The hydrolysis conditions were optimized using response surface methodology (RSM). We investigated two independent variables: the enzyme to substrate (E/S) ratio (0.59-3.41%, w/w) and the time taken for hydrolysis to occur (45-555 minutes). The E/S ratio and hydrolysis time significantly affected the yield, DPPH radical scavenging activity, metal chelating activity, degree of hydrolysis (DH), and average molecular weight (MW) of the protein hydrolysates. The optimum conditions for hydrolysis were an E/S ratio of 2.84% and 480 minutes for hydrolysis, which obtained a yield of 40.73 ± 0.44%, an IC50 value of 0.87 ± 0.02 mg/ml in the DPPH assay, a metal chelating activity of 72.80 ± 1.79%, a DH of 22.18 ± 0.42% and a MW of 3.07 ± 0.14 kDa. GRB protein hydrolysate, produced using alcalase, could have potential applications as an ingredient in functional food products due to its high antioxidative properties.