Manop Suphantharika

Preparation of spent brewer’s yeast β-glucans with a potential application as an immunostimulant for black tiger shrimp, Penaeus monodon

Spent brewers yeast was autolysed and the insoluble yeast cell wall fraction obtained was used as a raw material for the preparation of brewers yeast beta-glucan (BYG). A simple alkaline extraction was applied and optimized. The BYG with significantly (P</=0.05) high carbohydrate and glucan contents of 92% and 51% (w/w), respectively and with a low protein content of 1.6% (w/w) was obtained by a single alkaline extraction using 5 volumes of 1.0 N NaOH at 90 degrees C for 1 h. In vitro, this glucan significantly (P</=0.05) enhanced phenoloxidase (PO) activity of black tiger shrimp hemolymph as compared to controls without added glucan. Also in vivo, an oral administration of 0.2% (w/w) in diets for 3 days significantly (P</=0.05) increased the PO-activity of the shrimp. The potential immunostimulating properties of a commercial and other yeast-derived products were also evaluated for comparative purposes.

Bacteria Interface Pickering Emulsions Stabilized by Self-assembled Bacteria–Chitosan Network

An oil-in-water Pickering emulsion stabilized by biobased material based on a bacteria-chitosan network (BCN) was developed for the first time in this study. The formation of self-assembled BCN was possible due to the electrostatic interaction between negatively charged bacterial cells and polycationic chitosan. The BCN was proven to stabilize the tetradecane/water interface, promoting formation of highly stable oil-in-water emulsion (o/w emulsion). We characterized and visualized the BCN stabilized o/w emulsions by scanning electron microscopy (SEM) and laser scanning confocal microscopy (LSCM). Due to the sustainability and low environmental impact of chitosan, the BCN-based emulsions open up opportunities for the development of an environmental friendly new interface material as well as the novel type of microreactor utilizing bacterial cells network.

Glucan from spent brewer's yeast: preparation, analysis and use as a potential immunostimulant in shrimp feed

Spent brewers yeast was autolysed and the residual solids were further treated with hot alkali to produce a fraction containing 95% (w/w) carbohydrate, with a glycogen content of 42% and an apparent glucan content of ca. 53% (w/w). FTIR and solid state C-NMR spectra basically showed a spectrum characteristic for an impure β-glucan. In vitro, this glucan induced release of prophenoloxidase from intact black tiger shrimp haemocytes. When fed to shrimp at 0.2% (w/w of the feed) for 3 days, significant increases in phenol oxidase, the number of haemocytes and the bacterial killing activity against the pathogen Vibrio harveyi were observed. Furthermore, this feeding resulted in the appearance of an inducible β-(1,3)-glucanase in the liver. Methods to analyse the fractions are discussed and a number of commercial products with potential immune stimulating properties have been included for comparative purposes.

Effect of cross-linking on physicochemical properties of tapioca starch and its application in soup product

Physicochemical properties of cross-linked tapioca starch (CLTS) with different cross-linking levels and their application as a thickening agent in soups were studied. The CLTS was prepared by cross-linking native tapioca starch suspended in alkaline solution (41.67% (w/w), pH 11) using a mixture (99:1 (w/w) ratio) of sodium trimetaphosphate (STMP) and sodium tripolyphosphate (STPP) at different concentrations ranged from 0.25% to 6.0% (w/w of starch) at 45°C for 3h. Starch paste clarity decreased with increasing concentration of STMP/STPP mixture. Variations of swelling power, solubility, pasting, gelatinization, and rheological properties of the CLTS were found. Thermogravimetric analysis exhibited higher thermal stability for the CLTS granules compared to the native one. Among the samples, the CLTS prepared using 1.0% STMP/STPP (1.0%-CLTS) and soup containing the 1.0%-CLTS exhibited the strongest gel characteristic and the greatest shear resistant properties. The 1.0%-CLTS improved the textural properties and sensory quality of soups.

Slow glucose release property of enzyme-synthesized highly branched maltodextrins differs among starch sources

Seven types of starch (waxy corn, normal corn, waxy rice, normal rice, waxy potato, normal potato, and tapioca) were selected to produce slowly digestible maltodextrins by enzymatic modification using a previously developed procedure. Branching enzyme (BE) alone and in combination with β-amylase (BA) were used to increase the amount of α-1,6 branching points, which are slowly hydrolyzed by mucosal α-glucosidases in the small intestine. The enzymatic treatments of all starches resulted in a reduction of the debranched linear chain length distribution and weight-average molecular weight. After α-amylolysis of the enzymatically synthesized-maltodextrins, the proportion of branched α-limit dextrins increased, and consequently a reduction in rate of glucose release by rat intestinal α-glucosidases in vitro. Among the samples, enzyme-modified waxy starches had a more pronounced effect on an increase in the slow digestion property than normal starches. These enzyme-modified maltodextrins show potential as novel functional foods by slowing digestion rate to attain extended glucose release.

Characterization of Modified Tapioca Starch in Atmospheric Argon Plasma under Diverse Humidity by FTIR Spectroscopy

Tapioca is economical crop grown in Thailand and continues to be one of the major sources of starch. Nowadays, tapioca starch has been widely used in industrial applications, however the native form of starch has limited the applications. Thus scientists try to modify the properties of starch for increasing the stability of the granules, pastes to low pH, heat, and shear during the food process. We modify the tapioca starch by plasma treatment under an argon atmosphere. The degree of modification is determined by following water content in the starch granules. The tablet samples of native starch are also prepared and compared with the plasma treated starch. Before plasma treatment, the starch tablets are stored under three different relative humilities (RH) including 11%, 68%, and 78%RH, respectively. The samples are characterized using FTIR spectroscopy associated with the degree of cross-linking. The results show that the water molecules are engulfed into the starch structure in two ways, a tight bond and a weak absorption of water molecules which is represented at two wave number of 1630 cm−1 and 3272 cm−1, respectively. The degree of cross-linking can be identified from the relative intensity of these two peaks with the C—O—H peak at 993 cm−1. The results show that the degree of cross-linking increase in the plasma treated starch. The degree of cross-linking of the treated starch with high relative humidity is less than that of the treated starch with low relative humidity.

Application of a simple yeast extract from spent brewer's yeast for growth and sporulation of Bacillus thuringiensis subsp. kurstaki: a Physiological Study

The suitability of using a simple brewers yeast extract (BYE), prepared by autolysis of complete beer slurry, for growth and sporulation of Bacillus thuringiensis kurstaki was studied in baffled shake flasks. In a standard buffered medium with 2.5% (w/v) glucose and 1% (w/v) brewers yeast extract, growth of B. t. kurstaki resulted in a low biomass production with considerable byproduct formation, including organic acids and a concomitant low medium pH, incomplete glucose utilization and marginal sporulation, whereas growth in the same medium with a commercial laboratory-grade yeast extract (Difco) resulted in a high biomass concentration, complete glucose utilization, relatively low levels of byproducts and complete sporulation (2.6 × 109 spores/ml). When glucose was left out of the medium, however, growth parameters and sporulation were comparable for BYE and commercial yeast extract, but absolute biomass levels and spore counts were low. Iron was subsequently identified as a limiting factor in BYE. After addition of 3 mg iron sulphate/l, biomass formation in BYE-medium more than doubled, low byproduct formation was observed, and complete sporulation occurred (2.8 × 109spores/ml). These data were slightly lower than those obtained in media with commercial yeast extract (3.6 × 109spores/ml), which also benefited, but to a smaller extent, from addition of iron.

Modification of tapioca starch by non-chemical route using jet atmospheric argon plasma

Non-chemical modification of tapioca starch was investigated using jet atmospheric argon plasma treatment. Two forms of starch slurry, i.e. granular starch (G) and cooked starch (C), were jet-treated by argon plasma generated by supplying input power of 50 W (denoted as G50 and C50 samples) and 100 W (denoted as G100 and C100 samples) for 5 min. Physical, rheological, and structural characteristics of the modified starch were investigated. The G50 and C100 samples had lower paste clarity but higher thermal stability and performed stronger gels (G50 only) compared to their control counterparts. On the other hand, the analyzed properties of the G100 and C50 samples showed the opposite trend. FTIR and (1)H NMR results revealed that the relative areas of COC and OH peaks were changed after the treatment. Cross-linking reaction seemed to predominantly take place for the G50 and C100 samples, whereas depolymerization predominated for the G100 and C50 samples.

Preparation of 5′-GMP-rich yeast extracts from spent brewer's yeast

Spent brewers yeast was autolysed and used as a raw material for the preparation of 5′-GMP-rich yeast extracts. Malt rootlets were used as a source of 5′-phosphodiesterase. The crude enzyme was extracted from malt rootlets and pretreated to inactivate 5′-nucleotidase. The optimum pretreatment conditions were heating at 65 °C for 30 min or 70 °C for 7 min. The effects of autolysis time, phosphodiesterase concentration and incubation period on 5′-GMP content were examined. The suitable autolysis time was 8 h. The preferable enzyme treatment period was in the range of 8–14 h. Longer autolysis and enzyme incubation periods caused a decrease in the 5′-GMP content from 0.7–0.9% (w/w) to 0.2–0.4% (w/w). The 5′-GMP content in extracts from debittered and non-debittered yeast was similar. The highest 5′-GMP content in yeast extract was 0.93% (w/w), obtained with a phosphodiesterase concentration of 1.6unit/ml of yeast extract (5% solids content).

Effect of high pressure homogenization and papain on the preparation of autolysed yeast extract

The effect of high pressure homogenization (600 and 1000 bar) prior to autolysis of a commercial pressed bakers yeast was examined. High pressure homogenization released a maximum of 30% of the solids and 34% of the total nitrogen (TN). After autolysis of the whole homogenized slurry, high yields of solids and TN (up to 81 and 85%, respectively) were obtained. Autolysis of non-homogenized controls yielded much lower yield values (30 and 39%, respectively), whereas autolysis in the presence of papain but without prior disruption gave intermediate values (50 and 61%, respectively). The various treatments led to changes in the extract composition: standard autolysates had the highest total nitrogen and true protein weight contents and the lowest carbohydrate content, whereas this trend was reversed when cells were first disrupted before autolysis. In contrast to controls obtained by standard autolysis without or with papain, centrifuged autolysates from pre-homogenized fractions were not clear. Treatment with a combination of a flocculation and a weighting agent clarified the extracts but resulted in a loss of solids (approximately 20%), including nitrogen and carbohydrates.