Morphological, Structural, Thermal, and Rheological Characteristics of Starches Separated from Apples of Different Cultivars

Abstract

The starches were separated from unripe apples of five cultivars (Criterion, Ruspippum, Red Spur, Skyline Supreme, and Granny Smith) and evaluated using scanning electron microscopy (SEM), gel permeation chromatography (GPC), X-ray diffraction, differential scanning calorimetry (DSC), and dynamic viscoelasticity. SEM showed the presence of round granules as well as granules that had been partially degraded, probably by amylases. The starch granules in different apple starches ranged between 4.1 and 12.0 mum. Debranching of starch with isoamylase and subsequent fractionation of debranched materials by GPC revealed the presence of an apparent amylose, an intermediate fraction (mixture of amylose and amylopectin), long side chains of amylopectin, and short side chains of amylopectin in the range of 28-35.2, 3.6-4.4, 20-21.3, and 39.9-47.1%, respectively. The swelling power of starches ranged between 14.4 and 21.3 g/g. X-ray diffraction of apple starches showed a mixture of A- and B-type patterns. All apple starches showed peak intensities lower than that observed for normal corn and potato starch, indicating the lower crystallinity. The transition temperatures (onset temperature, T(o); peak temperature, T(p); and conclusion temperature, T(c)) and enthalpy of gelatinization (deltaH(gel)) determined using DSC ranged between 54.7 and 56.2 degrees C, between 57.1 and 59.1 degrees C, between 60.2 and 63.5 degrees C, and between 3.3 and 4.2 J/g, respectively. The viscoelastic properties of starch from different cultivars measured during heating and cooling using a rheometer differed significantly. Red Spur and Criterion starches with larger granule size showed higher G' and G' ' values, whereas those containing smaller size and amylolytically degraded granules showed lower G' and G' '.

Impact of the Soak and the Malt on the Physicochemical Properties of the Sorghum Starches

“…At temperatures between 90 and 70 °C, traces of G′ and G″ remained relatively flat, consistent with what has been reported for cultivars of rice and apple [28]. All samples of malted sorghum exhibited low peaks in shear modulus, in contrast, the corresponding traces for RG and 24hSG were relatively steep forming a sigmoidal pattern of modulus development.…”

Structure and Physicochemical Properties of Starches from Sieve Fractions of Oat Flour Compared with Whole and Pin‐Milled Flour

“…The shorter average amylopectin branch chain lengths observed for pin-milled oat starch compared with starch from entire kernels, corroborates analysis of amylopectin density that pin-milling may degrade exterior chains that have longer polymerization. Presence of long side chains in amylopectin have been reported (Reddy et al 1993;Takeda et al 1993Takeda et al , 1999Singh et al 2005), although Matheson (1996) found amylopectin density can increase by lengthening ci-glucan chains in the external, internal, or core molecular regions. Repeated, lengthy ball-milling of the wheat starch converted some amylopectin to low molecular weight fragments that were derived from shearing glycosidic bonds in the long 132, 133, and 134 internal chains (Morrison and Tester 1994).…”

Isolation and physicochemical characterisation of starch from cocoyam (Colocasia esculenta) grown in Malawi

“…Size distributions of the starch granules were estimated by classifying the size of starch granules into four groups: large (>25 µm), medium (10-25 µm), small (5-10 µm) and very small (<5 µm). 14 Reducing capacity, iodine absorption spectra and blue value The starch samples for the determination of reducing capacity were prepared according to the method of Singh et al 15 and the reducing capacity of the starch samples was determined (as glucose equivalent) using the modified Park and Johnson method. 16 Iodine spectra of the native starches were determined following the dimethyl sulfoxide-urea method 17 and the blue value (BV) was measured as absorbance at 680 nm.…”