Acid Thinning Research Articles

Influence of chemical modifications on dynamic rheological behaviour, thermal techno-functionalities, morpho-structural characteristics and prebiotic activity of banana starches

Banana starch is explored for its use in food and pharmaceutical applications. In this study, in order to improve the techno-functional properties of native banana starch (NS), different chemical modifications namely acid thinning (AT), oxidation (OX), sodium-trimetaphosphate method (STMP), cross linking phosphorylation (CLP), hydroxypropylation (HYP) were employed. Among the modified starches, amylose content was higher in CLP starch and the least was observed in AT. Resistant starch (RS) of HYP (65.38 %) and CLP starches (62.76 %) were significantly higher than other modified starches. Lesser amylose, higher water solubility and lower swelling of AT starch resulted in inferior paste clarity and inability to make a firm gel. Non-Newtonian behaviour of starch gels were observed from static viscosity observations. The dynamic rheological behaviour of the starch gels affirmed the higher gel strength of STMP (0.46) and CLP (0.56) starches. Imperfection and exo-corrosion in starch morphology was observed through SEM and influence of chemicals on the starch structure was elucidated through FTIR and XRD analyses. Except AT starch, modified starches with higher RS resulted in lowering glycemic index (57–69 %). STMP starches recorded highest prebiotic activity score of 0.88. Chemical modifications enable to enhance the functionalities of banana starch and offers potential industrial uses.

Modification of Starches with Different Amylose/Amylopectin Ratios Using the Dual Approach with Hydroxypropylation and Subsequent Acid Thinning—III: Impacts on Gel Characteristics

AbstractStarches with different amylose (AM)/amylopectin (AP) ratios (waxy potato: WxPS, regular potato: PS, high AM corn: HACS) are subjected to hydroxypropylation (HP, two levels) and subsequent acid‐thinning (AT) to produce dual modified samples. Pastes of the starch samples (native; single modification: HP and AT, respectively; dual modification) are prepared by pressure cooking to two different starch concentrations (C) (6% and 9% w/w) and systematically investigated especially in terms of light transmittance (T) and specific gel characteristics after long‐term cold storage (168 h at 5.5 ± 1.5 °C). The data are evaluated statistically (i.a. analysis of variance, ANOVA) and significant effects are identified. Indeed, the gel strength correlates positively with the AM content of the starch and C, but the HP eliminates the ability of the starch to gel in most cases. The improved Tgel due to HP is accompanied by extensive loss of mechanical strength in most cases, which is not compensated by the partial molecular degradation via AT. Hence, a synergistic effect of both modifications is not revealed. The synergistic implementation of a starch with the desired properties by preparing mixtures is not revealed during the present examinations.

The supporting effect of ultrasound on the acid hydrolysis of granular potato starch

The modification of starch owing to acid-thinning (AT) is intensified by a concomitant ultrasound (US) treatment, but the specific effect of the US on molecular changes, and the respective contribution of the single impacts are still unknown. The present study investigates the supporting effect of the US via examination and comparison of the single modifications [general conditions: starch slurry (40 % w/w), 40 °C, stirring; US: gradation of amplitude (50 and 100 %), cycle (0.50 and 0.75) and sonication time (20 and 60 min); AT: 0.36 M HCl, reaction time of 4 h] with the corresponding US assisted AT modified starches (US-AT) in terms of granular, molecular and functional properties. The US induced essentially a molecular degradation (debranching) of the amylopectin (AP), whereas chain cleavage within the amylose (AM) wasn’t excluded completely. Altogether, the US was estimated to be a separate and assisting modification rather than an AT accelerating component.