Effect of Physical Pretreatments on the Hydrolysis Kinetic, Structural, and Thermal Properties of Pinhão Starch Nanocrystals

Abstract

Starch nanocrystals (SNCs) are insoluble platelet particles with multifunctional properties. SNCs production is mainly based on acid hydrolysis of cornstarch with low yield. This study focuses on investigating the effect of pretreatments (heat‐moisture‐treatment [HMT], annealing [ANN], and sonication [SNT]) on unconventional pinhão starch to produce SNCs by acid hydrolysis to improve the yield and SNCs properties. All starches hydrolysis is described by a first‐order model reaction and shown two phases related at k values. The faster hydrolysis is from SNT (k = 0.61 day−1) and the slower one is at ANN (k = 0.40 day−1). Furthermore, the acid hydrolysis is described by a rapid (0–2 days) phase, followed by a slow phase lasing 3–7 days. The HMT increases the yield of the SNCs (14.7%) but promotes losses in the RC (47.34%) as compared with the native starch (yield 10.23%; RC 52.23%). The ANN improves crystallites perfection, protecting them from acid attack. The pretreatments allow pinhão starch to be used as promising feedstock to produce SNCs with good yield and RC. In addition, ANN can be useful to improve the thermal stability and SNT to speeding up the hydrolysis for SNCs production, while HMT can increase the hydrolysis yield.

Physical Pretreatment on Common Bean Starch at Acid Hydrolyzed Nanocrystals Structure and Properties

“…[13] Moreover, pretreatments such as HMT, ANN, and SNT were used in isolated pinhão SNC through H 2 SO 4 hydrolysis, resulting in an increased SNC yield by HMT, speeding up the SNC production by SNT and improving the thermal stability of SNC by ANN. [14] These findings indicate that combining acid hydrolysis and some preliminary physical treatments, such as HMT, ANN, and SNT can enhance the efficiency of SNC production and its properties. [12][13][14] The waxy starch is preferred to produce SNC due to its naturally low amylose content [9][10][11]15,19] although this nanomaterial can be derived from various starch sources, including cereals, pulses, and tubers.…”

“…[14] These findings indicate that combining acid hydrolysis and some preliminary physical treatments, such as HMT, ANN, and SNT can enhance the efficiency of SNC production and its properties. [12][13][14] The waxy starch is preferred to produce SNC due to its naturally low amylose content [9][10][11]15,19] although this nanomaterial can be derived from various starch sources, including cereals, pulses, and tubers. However, it is noteworthy that the SNCs obtained from pulses are not as studied as other types of starch.…”

“…where C f , starch hydrolyzed at the time; C 0 , initial starch hydrolysates (%); t, hydrolysis time (days); k, first-order rate constant (day −1 ) calculated by non-linear regression, using the Levenberg-Marquardt iteration algorithm. The hydrolysis rate constant changes were observed using the Logarithm of Slope (LOS) technique by transforming the first derivative of the first-order equation into the logarithmic form of Equation ( 1) and obtaining a linear model (Equation ( 3)) to depict the various stages in the hydrolysis process [13,14] ln…”

“…Physical treatments and acid hydrolysis combination are promising approaches for SNC production. [12][13][14][15][16][17] For instance, heat-moisture-treatment (HMT), annealing (ANN), and sonication (SNT) are commonly used physical modifications used to improve and expand applications of starches. Both HMT and ANN are hydrothermal modifications able to promote some structural changes, particularly in extending double helical lengths, reducing double helix content, strengthening amylose-amylose and amylopectin-amylopectin interactions, and affecting chains flexibility and the heterogeneity of semi-crystalline lamellae.…”

“…The Carioca bean starch shows a C-type crystallinity pattern and a relative crystallinity (RC) of about 26%. [28] In general, native starches A-or C-type polymorphs display enhanced resistance to acid hydrolysis than the B-type starches [14,23] resulting in different hydrolysis patterns and SNC yield. Moreover, physically treated Carioca bean starches have shown improved thermal resistance and slight decreases in RC dependent on the treatment, [28] which we believe can reflect on SNC properties.…”