Yuthana Phimolsiripol

Nonthermal plasma for pesticide and microbial elimination on fruits and vegetables: an overview

Summary Nonthermal plasma (NTP) is defined in terms of partly ionised gas which overall temperature is quite low because the stored energy is mostly in free electrons. Applications of NTP have been expanded to new areas of food applications such as the microbial inactivation and also the elimination of pesticide and toxic chemical residues in food such as fruits and vegetables while nutritional content and key characteristics are still preserved. Plasma treatment has successfully decreased the concentrations of pesticides by about 45-71%. In this article, NTP technologies as well as investigations about applying of NTP for removing pesticide residues and improving microbial safety in fresh produce are described. Potential applications of NTP in food processing together with some of their challenges and limitations are also discussed.

Antioxidant and immunomodulatory activities of sulphated polysaccharides from purple glutinous rice bran (Oryza sativa L.)

Summary This research aimed to extract polysaccharides and improve the property of sulphate-modified purple glutinous rice bran, cv. Kum Doi Saket. The effects of temperature, ratio of sulphur trioxide–trimethylamine (STMA) to sample and reaction times were studied. The results showed that the degree of substitution (DS) of sulphated polysaccharides was 0.01–0.53. Low molecular weight sulphated polysaccharides were obtained, and the functional groups of the sulphated polysaccharides were confirmed using FT-IR. No enhancement of the antioxidant activity of the sulphated polysaccharides was observed. Interestingly, immunomodulatory activity, including inducing cytokine production (iNOS, TNF-α, IL-1β and IL-10) via up-regulated mRNA expression, was significantly increased by 10–86% when compared to the crude polysaccharides.

Effect of extraction and concentration processes on properties of longan syrup

Longan (Dimocarpus longan Lour.) syrup is a novel liquid sweetener produced from longan, one of the traditional and economic fruits in the Northern of Thailand. In this research, the effect of extraction and concentration processes on properties of longan syrup was investigated. There were two extraction methods (juice extractor and hydraulic press) and three concentration methods (direct heating, steam heating and vacuum evaporation). Results overall showed that the extraction method had no significant (p ≥ 0.05) effect on longan syrup properties, while concentration resulted in the quality changes of longan syrup. Concentration using direct heating of longan juice caused reduction of sucrose content, and longan syrup dark in color. The headspace volatile compounds of longan syrup were sampled using direct headspace technique and further characterized using gas chromatography-mass spectrometry. The identified volatile compounds could be divided into two groups of aroma characteristics which were (1) floral aroma: 3-methybutyl acetate, (β)-ocimene and 2-phenylethyl alcohol and (2) caramel aroma: butyraldehyde, furfural and benzaldehyde. 2-Phenylethyl alcohol, contributing to floral odor, was retained using vacuum evaporation as a concentration method. Result revealed that the optimal concentration process for longan syrup production was vacuum evaporation, providing the highest floral volatile and lowest caramel volatile. Sensory tests confirmed that longan flavor of the syrup produced from the vacuum evaporation process had significantly higher hedonic scores than other processes.

Response Surface Optimization of Exopolysaccharide Production from Sugarcane Juice by Lactobacillus confusus TISTR 1498

Lactobacillus confusus TISTR 1498, isolated from Thai traditional fermented pork (Nham), could secrete large amounts of exopolysaccharides (EPS). Response surface methodology was applied to optimize the culture condi- tions for EPS production using Central Composite Design (CCD). The effects of three variables including pH (4-7), temperature (20-40°C) and nitrogen source (0.25-1.75 PYB) on EPS yield and biomass were investigated. The 1PYB was the mixtures of 5 g/L peptone (P), 2.5 g/L yeast extract (Y) and 2.5 g/L beef extract (B). Response surface methodology showed that the data were adequately fitted to a second-order polynomial model via quadratic regression relationships. The optimal culture conditions for EPS production in sugarcane juice were pH of 5.55, 29.75°C and 1.22PYB, which was composed of 6.1 g/L peptone, 3.05 g/L yeast extract and 3.05 g/L beef extract. Under the optimum condition, the pre- dicted maximum EPS production was 107.5 g/L and the predicted biomass was 1.92 g/L. In submerged fermentation, sugarcane juice enhanced EPS yield twice as well as the modified MRS sucrose medium. In addition, the cost of medium can be lowered to 0.53 THB/g EPS, which was lower than that of the medium from the mixtures of the PYB (0.78 THB/gEPS).

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.