Hom-keak onion (Allium cepa var. viviparum) has a high potential to serve as a functional food. This research developed 1) production of Hom-keak onion by tissue culture technique 2) production of concentrated fructooligosaccharide syrup from Hom-kaek onion 3) evaluation of the prebiotic properties of Hom-kaek onion fructooligosacchride syrup in simulating human gut model 4) examination of biological activities of Hom-kaek onion 5) Ethanol production from residue obtained from Hom-kaek syrup processing.
Production of Hom-keak onion by tissue culture technique, initiation phase, onion bulbs were sterilized using 25% Clorox?, 0.1% mercuric chloride, 1% silver nitrate, or 6% hydrogen. cutting the onion bulb into 8 sections, the averages of 1.31 shoots per explant and 6.4 shoots per initial bulb were observed. The modified semi-solid MS medium with 1.0 mg/L indole-3-butyric acid (IBA) was the most efficient for root induction and two weeks of root induction period prior to the plantlet transfer was the most optimal time, yielding an 85.71% survival rate. Additionally, the different planting materials were compared. It was found that the latter formula (1:1:3:3 loam: sand: rice husk ash: peat moss) led to the highest survival rates of the onion plantlets and the highest growth.
Development of the semi-industrial production of fructooligosaccharide syrup (FOS) from onion and study chemical, physical and some biological properties of the developed product. Results showed that the sugar content of onion was 7.5% fresh weight, or 22.8% dry weight, and was rich with oligosaccharides. Bacteria, yeasts and molds were contaminated on onion’s surface, but the growth of microorganisms was controlled by cold temperature (4?C). This project was successfully developing the equipment for cleaning, pressing, and screening. The capacity of cleaning machine with whirlpool system was more than 20 kg/batch. Most of microorganisms were killed in 4 minutes when sodium hypochlorite solution (50 ppm) was associated in cleaning step. The operating rate ofthe pressing and screening machines was 8.3 kg/hr and 6.5 l/hr. Clarity of onion juice was increased (80%) after screening.
Hom-kaek onion fructooligosacchride syrup was used as prebiotic substance and evaluated prebiotic properties in simulating human gut model. The digestibility evaluation results revealed that fructooligosacchride syrup were resistant toward the simulated oral, gastric, and intestinal conditions. Fermentation of the fructooligosacchride syrup in human gut model was conducted using fecal slurry from healthy infant as the representative of natural inoculum. The results found that the most abundance bacteria which were selectively simulated by the fructooligosacchride syrup belonged to phylum Actinobacteria such as Bifidobacterium sp. Moreover, the results revealed that the major fermentative carbon sources were the contaminated glucose, fructose and sucrose, the retained residues after the purification of fructooligosacchride syrup, two different fructooligosacchrides including kestose and an unidentified saccharide with a polarity that is closely related to kestose as judged by TLC technique.
Biological activities of fresh onion extract (F), fructooligosaccharide syrup extract (H), and absorbent fructooligosaccharide syrup extract (HC) were examined. The result found that F extract could inhibit Bacillus cereus. The H extract showed highest total phenolic content and highest antioxidant activity. In an assay for the anti-inflammatory effects, we found that 1,000 ?g/mL of the H extract and the HC extract inhibited the cytokine IL-6 secretion. The cytotoxicity of the onion extract on human skin cells type fibroblasts (WS1) and colon cancer cells (Caco2) were evaluated. The HC extract had the lowest toxicity on both WS1 and Caco2 cells, the F extract had the highest toxicity on WS1. The heated juice was also studied, cytokine IL-6 and cytokine TNF-? secretion was exhibited by the juice. The juice exhibited low toxicity to WS1 and Caco2 cells. The result indicated that the onion can be cooked or subject to heat during food processing without a loss of bioactive compounds.Onion residue is a waste from onion syrup process. Cellulose is a component of the wastes which could be hydrolyzed to fermentable sugar for ethanol production. The optimal conditions for onion waste hydrolysis were 3.0 % HCl with heating at 121 oC for 60 min. After acid hydrolysis, the onion waste was then incubated by cellulase with 12,000 U/ml at 30 oC for 3 hours released reducing sugar 3.75 mg/ml. Fermentation, the reducing sugar was concentrated to 20 oBrix for ethanol fermentation, yeast extract 10 g/ml, urea 6.4 g/ml, KH2PO4 1 g/ml and MgSO4.7H20 10 g/ml were added. Saccharomyces cerevisiae TISTR 5339 with 3.24 ? 106 cell/ml was cultured. Highest alcohol content with 5% (v/v) was produced at day 3 of cultivation.