Saiyavit Varavinit

A Study of Some Physicochemical Properties of High-Crystalline Tapioca Starch

Tapioca starch was partially hydrolyzed in hydrochloric acid solution at room temperature for various lengths of time to obtain high-crystalline starches. RVA viscoamylograms of acid-modified starches demonstrated a very low viscosity as compared to that of native tapioca starch. The relative crystallinity of native and acid-modified tapioca starches were measured by X-ray diffraction ranging from 39.53% to 57.75%. The native and acid-modified tapioca starches were compressed into tablets using various compression forces. The % relative crystallinity of starch increased with the increase in hydrolysis time and the crushing strength of the tablet was also increased in line with the crystallinity while the amylose content decreased when the crystallinity increased. These results suggested that the erosion of amylose might cause the rearrangement of starch structure into a new more tightly packed form, which provided the higher crushing strength for the tablets.

Characterization and utilization of acid-modified cross-linked Tapioca starch in pharmaceutical tablets

Tapioca starch was cross-linked in the presence of alkaline sodium trimetaphosphate solution. The cross-linked tapioca starch was hydrolyzed by 6% (w/v) HCl solution at room temperature for 192 h. The final product was dried by centrifugal spray dryer to obtain agglomerated acid-modified cross-linked tapioca starch. Spray-dried native tapioca starch, cross-linked tapioca starch and acid-modified tapioca starch were also studied parallel with that of acid-modified cross-linked tapioca starch. It was found that cross-linking didnt increase the relative crystallinity or the melting enthalpy of tapioca starch. Compression of both native and cross-linked tapioca starches gave tablets with a very low crushing strength. Acid hydrolysis introduced to remove the amorphous regions in order to increase the crystallinity of both types of starches, resulting in tablets with a higher crushing strength. In this respect tablets prepared from acid-modified cross-linked tapioca starch were better than those prepared from acid-modified tapioca starch.

Increasing Slowly Digestible Starch Content of Normal and Waxy Maize Starches and Properties of Starch Products

ABSTRACT Changes in the digestibility and the properties of the starch isolated from normal and waxy maize kernels after heat-moisture treatment (HMT) followed by different temperature cycling (TC) or isothermal holding (IH) conditions were investigated. Moist maize kernels were heated at 80°C for 2 hr. The HMT maize kernels were subjected to various conditions designed to accelerate retrogradation of the starch within endosperm cells. Two methods were used to accelerate crystallization: TC with a low temperature of –24°C for 1 hr and a high temperature of 20, 30, or 50°C for 2, 4, or 24 hr for 1, 2, or 4 cycles, and IH at 4, 20, 30, or 50°C for 24 hr. The starch granules were then isolated from the treated kernels. The starch isolated from HMT normal maize kernels treated by TC using –24°C for 1 hr and 30°C for 2 hr for 2 cycles gave the greatest SDS content (24%) and starch yield (54%). The starch isolated from HMT waxy maize kernels treated by TC using –24°C for 1 hr and 30°C for 24 hr for 1 cycle had ...

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.

A study of annealing and freeze-thaw stability of acid-modified tapioca starches by Differential Scanning Calorimetry (DSC)

Tapioca starch was partially hydrolyzed by 6% (w/v) hydrochloric acid at room temperature for various lengths of time. Annealing and freeze-thaw stability of the acid-modified starches were studied using Differential Scanning Calorimetry (DSC). In the annealing study, as the hydrolysis time increased, the effect of annealing on narrowing and shifting the endothermic peak to a higher temperature was decreased. The endothermic transition of annealed 48-h acid-modified tapioca starch showed a narrow peak and a broad shoulder, corresponding to the melting of the amylopectin double helices (crystalline regions) and the retrograded partially hydrolyzed amylose, respectively. This effect of annealing on the sharpening of the endotherm was less pronounced on acid-modified tapioca starches annealed for 192 h and 768 h, respectively. These results indicated that annealing leads to more homogeneous crystallites and this effect is enhanced when the material contains more amorphous and homogeneous domains. In the case of the freeze-thaw stability study, the melting endotherm of recrystallized amylopectin became larger with increasing hydrolysis time. The first detectable endotherm of native tapioca retrograded gel was observed after five cycles, while all acid-modified retrograded gels showed the melting endotherm after only one cycle. Increasing hydrolysis time may increase the proportion of short chain amylose and amylopectin molecules, which are able to form double helices, resulting in an increase in the enthalpy and a higher retrogradation rate of the gel.

Production of 6-Aminopenicillanic Acid by an Enzymatic Process

6-APA can be produced by converting penicillin-G into 6-APA and phenylacetic acid with penicillin acylase (PA) enzyme. The genes encoding PA were cloned from Escherichi a £2li and Bacillus megaterium. £. £2li transformants containing the £. CQli PA gene produce around 10 times higher enzyme activity than the parent cells. £. sutililis transformants containing the fi. megaterium PA gene produce around twice the enzyme activity of the parent cells. Restriction maps and sizes of the two PA genes are different. Attempts to increase gene expression by using strong promoters were partially successful. The £. cfili transformant (pMLV6) has been Immobilized on cotton threads with calcium alginate, resulting in a relatively small loss in enzymatic activity. The immobilized cells were quite stable when kept at 4°C and/or occasionally used (with less than 10% loss in activity) over a period of 5 months. When used for converting penicillin-G (15 liters of 6-8% commercial crude penicillin-G), 5 Kg of immobilized cells were needed to give a conversion of around 98% in 3-4 hours at 35°C. Crystallization of the 6-APA produced was achieved by using 3350% methanol, lowering the pH to 4.2 and cooling to -5°C. Percent recovery of the crystallized 6-APA obtained was around 70-80%.