The Role of Reaction Parameters on the Preparation and Properties of Carboxymethyl Cassava Starch

The role of reaction variables on carboxymethylation of cassava starch was investigated using a statistically experimental design approach. The reaction was carried out in an isopropanol‐water mixture at 40°C for 3 h. The reaction parameters under investigation included water fraction in the reaction medium, the ratio of sodium hydroxide to anhydroglucose unit (AGU) and the ratio of sodium monochloroacetate (SMCA) to AGU. The dependent responses were degree of substitution (DS) of CMS and the reaction efficiency (RE) of the carboxymethylation. Carboxymethyl cassava starches with DS in the range of 0.01 to 0.86 were prepared. The result from regression analysis indicated that the most important factors in controlling the DS of CMS were sodium hydroxide and SMCA contents followed by water content. Response surface plots suggested that the optimal levels of sodium hydroxide and water content to achieve CMS with high DS were at the intermediate values. Similar effects of sodium hydroxide and water content were also observed on the RE while SMCA content had a negative effect; increasing SMCA content resulted in lower RE. The optimal conditions to achieve the highest DS and RE were found to be at a water content of 17–19% with a molar ratio of sodium hydroxide to AGU of 1.8–1.9 and a molar ratio of SMCA to AGU between 1.1–1.5. Carboxymethyl cassava starch with various DS was also prepared. The properties of CMS as affected by the degree of modification were also discussed.     

Characterization of pectin extracted from banana peels of different varieties

Pectins were extracted from banana peels of five different varieties using citric acid solution. The chemical characteristics of banana peel pectins were investigated and compared with citrus peel and apple pomace pectins which were extracted under the same extraction conditions to assess the potential of banana peels as an alternative source of commercial pectin. The yield of banana peel pectins ranged from 15.89 to 24.08%. The extracted banana peel pectins were categorized as high methoxyl pectin with the degree of esterification between 63.15 and 72.03% comparable to those of conventional pectin sources from citrus peel (62.83%) and apple pomace (58.44%). The anhydrouronic acid (AUA) content of banana peel pectins varied from 34.56 to 66.67%. Among various banana varieties being studied, pectin from Kluai Nam Wa variety had the highest AUA content (66.67%) which met the criteria for food additive pectin indicating its commercial significance as an alternative pectin source.     

Tara tannin as active ingredient in electrospun fibrous delivery system

This study evaluated the releasing performance of tara tannin, a cocktail of plant polyphenols, incorporated in submicron fiber, produced by the electrospinning process. Polylactic acid was used as a polymer matrix that carried two loading levels of tara tannin, 14.3 and 22.3% dry weight in the final product. The fiber diameter of composite fibers was in the range 500–700 nm. The release of tara tannin was controlled by material attachment as there was no evidence of chemical bonding between materials. This was further confirmed by FTIR and DSC. From the five combinations of acid that were presented in tara tannin, galloylquinic acid, with the smallest molecular weight composition, was released in the largest proportion (%molar) and exhibited antioxidant activity. This was confirmed by 2,2‐diphenyl‐1‐picrylhydrazyl assay and HPLC‐MS analyses. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43646.     

Physicochemical Properties of Oxidized Cassava Starch Prepared under Various Alkalinity Levels

The physicochemical properties of hypochlorite‐oxidized cassava starch as influenced by the alkalinity levels (pH 8 to 11) during modification process were investigated. Hypochlorite oxidation generally increased the contents of carbonyl and carboxyl groups in starch but decreased starch viscosity. The formation of carbonyl and carboxyl groups was more favorable under the milder alkaline conditions (pH 8 and 9). Oxidation conducted at higher alkalinity levels produced both functional groups at a much slower rate and to a lesser extent. Starch viscosity decreased markedly with increasing reaction time. The alkalinity levels during the modification process greatly influenced the initial viscosity of the oxidized starch paste and the viscosity stability of the paste during storage. Thermal behavior studies by differential scanning calorimetry (DSC) demonstrated that oxidation decreased both gelatinization temperature and enthalpy. The decrease in gelatinization temperature was strongly related to the carboxyl group content. The more carboxyl groups the oxidized starch contained, the lower was the gelatinization temperature. Retrogradation of amylopectin tended to increase slightly after oxidation. While the light transmittance of native starch paste drastically decreased during cold storage, the changes observed in oxidized starch pastes were less pronounced and appeared to depend on carboxyl content. The results from light transmittance studies suggested that carboxyl groups introduced into the starch molecules could effectively prevent retrogradation.