Structure of faba bean, black bean and pinto bean starches at different levels of granule organization and their physicochemical properties

Understanding Starch Structure: Recent Progress

Starch is a major food supply for humanity. It is produced in seeds, rhizomes, roots and tubers in the form of semi-crystalline granules with unique properties for each plant. Though the size and morphology of the granules is specific for each plant species, their internal structures have remarkably similar architecture, consisting of growth rings, blocklets, and crystalline and amorphous lamellae. The basic components of starch granules are two polyglucans, namely amylose and amylopectin. The molecular structure of amylose is comparatively simple as it consists of glucose residues connected through α-(1,4)-linkages to long chains with a few α-(1,6)-branches. Amylopectin, which is the major component, has the same basic structure, but it has considerably shorter chains and a lot of α-(1,6)-branches. This results in a very complex, three-dimensional structure, the nature of which remains uncertain. Several models of the amylopectin structure have been suggested through the years, and in this review two models are described, namely the “cluster model” and the “building block backbone model”. The structure of the starch granules is discussed in light of both models.

C-type starches and their derivatives: structure and function

The C-type starches are widely distributed in seeds or rhizomes of various legumes, medicinal plants, and crops. These carbohydrate polymers directly affect the application of starchy plant resources. The structural and crystal properties of starches are crucial parameters of starch granules, which significantly influence their physicochemical and mechanical properties. The unique crystal structure consisting of both A- and B-type polymorphs endows C-type starches with specific crystal adjustability. Furthermore, large proportions of resistant starches and slowly digestible starches are C-type starches, which contribute to benign glycemic response and proliferation of gut microflora. Here, we review the distribution of C-type starches in various plant sources, the structural models and crystal properties of C-type starches, and the behavior and functionality relevant to modified C-type starches. We outline recent advances, potential applications, and limitations of C-type starches in industry, aiming to provide a theoretical basis for further research and to broaden the prospects of its applications.

Impact of molecular structure on the physicochemical properties of starches isolated from different field pea (Pisum sativum L.) cultivars grown in Saskatchewan, Canada

The objective of this study was to determine the molecular structure and properties of recently released cultivars of field peas [CDC Golden (CDCG), Abarth (ABAR), CDC Patrick (CDCP) and CDC Amarillo (CDCA)] grown at different locations in Saskatchewan, Canada. Starch yield (on whole seed basis), apparent amylose, total lipid and specific surface area were in the range 34-37%, 38.2-42.6%, 1.07-1.38% and 0.31-0.38m2/g, respectively. The proportion of short (DP 6-12) amylopectin chains, amylopectin branching density, molecular order, crystallinity, crystalline heterogeneity, gelatinization transition temperatures, pasting temperatures, peak viscosity, extent of acid hydrolysis, and resistant starch content were higher in CDCG and ABAR. However, amylopectin long chains (DP 13-26), average chain length and thermal stability were higher in CDCP and CDCA. The results of this study showed that differences in physicochemical properties among cultivars were mainly influenced by amylopectin chain length distribution, amylopectin branching density and co-crystallization of amylose with amylopectin.

Catalytic Transesterification of Starch with Plant Oils: A Sustainable and Efficient Route to Fatty Acid Starch Esters

The transesterification of maize starch with olive oil or high oleic sunflower oil was studied under homogeneous conditions in the presence of 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) as catalyst. Most importantly, this method used two renewable resources directly, without any pretreatment or derivatization, for the synthesis of polymeric materials with desirable properties. Moreover, the solvent, oils, and catalyst could be recovered through facile work-up and reused for further modifications. The obtained fatty acid starch esters (FASEs) were highly soluble in common organic solvents and were thoroughly characterized. Degrees of substitution (DS) were calculated using ³¹ P NMR spectroscopy, and DS values of approximately 1.3 were obtained. Differential scanning calorimetry analysis revealed thermal transitions of the modified starches at approximately 80-90 °C. Films were produced from these FASEs, and their hydrophobic surfaces were characterized using contact-angle measurements. Furthermore, mechanical properties were examined using tensile strength measurements and showed approximately 40 and 80 % elongation at break for modified maize starch and modified amylose from maize, respectively.

Recent progress in chemical modification of starch and its applications

Starch has received much attention as a promising natural material both in biomedical fields and waste water treatment due to its unique biological and adsorptive properties.

Starch chain interactions within the amorphous and crystalline domains of pulse starches during heat-moisture treatment at different temperatures and their impact on physicochemical properties

Pulse (faba bean [FB], black bean [BB] and pinto bean [PB]) starches were heat-moisture treated (HMT) at 80, 100 and 120°C for 12h at a moisture content of ∼23%. Structural changes on HMT were monitored by microscopy, HPAEC-PAD, ATR-FTIR, WAXS, DSC and susceptibility towards acid and enzyme hydrolysis. Amylopectin chain length distribution remained unchanged in all starches on HMT. In all starches, HMT increased crystallinity and gelatinisation temperatures. The gelatinization enthalpy remained unchanged in some starches, whereas it decreased slightly in other starches on HMT. Slowly digestible starch content decreased at all temperatures of HMT, whereas resistant starch content increased at HMT80 and HMT100 (HMT80>HMT100), but decreased at HMT120. Birefringence, B-type crystallites and acid hydrolysis decreased on HMT. The extent of the above changes varied amongst starch sources and genotypes. HMT altered the X-ray pattern from A+B→A. The results of this study showed that structural reorganisation of starch chains during HMT temperature was influenced by starch chain flexibility, starch chain interactions and crystalline stability of the native granules.

Physicochemical and functional characteristics of lentil starch

The physicochemical properties of lentil starch were measured and linked up with its functional properties and compared with those of corn and potato starches. The amylose content of lentil starch was the highest among these starches. The crystallinity and gelatinization enthalpy of lentil starch were the lowest among these starches. The high amylose: amylopectin ratio in lentil starch resulted into low crystallinity and gelatinization enthalpy. Gelatinization and pasting temperatures of lentil starch were in between those of corn and potato starches. Lentil starch gels showed the highest storage modulus, gel strength and pasting viscosity than corn and potato starch gels. Peleg's model was able to predict the stress relaxation data of these starches well (R(2)>0.98). The elastic modulus of lentil starch gel was less frequency dependent and higher in magnitude at high temperature (60 °C) than at lower temperature (10 °C). Lentil starch is suitable where higher gel strengthened pasting viscosity are desired.