Structure and genetic regulation of starch formation in sorghum (Sorghum bicolor (L.) Moench) endosperm: A review

This review focuses on the structure and genetic regulation of starch formation in sorghum (Sorghum bicolor (L.) Moench) endosperm. Sorghum is an important cereal crop that is well suited to grow in regions with high temperatures and limited water resources due to its C4 metabolism. The endosperm of sorghum kernels is a rich source of starch, which is composed of two main components: amylose and amylopectin. The synthesis of starch in sorghum endosperm involves multiple enzymatic reactions, which are regulated by complex genetic and environmental factors. Recent research has identified several genes involved in the regulation of starch synthesis in sorghum endosperm. In addition, the structure and properties of sorghum starch can also be influenced by environmental factors such as temperature, water availability, and soil nutrients. A better understanding of the structure and genetic regulation of starch formation in sorghum endosperm can have important implications for the development of sorghum-based products with improved quality and nutritional value. This review provides a comprehensive summary of the current knowledge on the structure and genetic regulation of starch formation in sorghum endosperm and highlights the potential for future research to further improve our understanding of this important process.

Rapid Ultrasound-Assisted Starch Extraction from Sago Pith Waste (SPW) for the Fabrication of Sustainable Bioplastic Film

The present study was conducted to optimize the extraction yield of starch from sago (Metroxylon sagu) pith waste (SPW) with the assistance of ultrasound ensued by the transformation of extracted starch into a higher value-added bioplastic film. Sago starch with extraction yield of 71.4% was successfully obtained using the ultrasound-assisted extraction, with the following conditions: particle size <250 µm, solid loading of 10 wt.%, ultrasonic amplitude of 70% and duty cycle of 83% in 5 min. The rapid ultrasound approach was proven to be more effective than the conventional extraction with 60.9% extraction yield in 30 min. Ultrasound-extracted starch was found to exhibit higher starch purity than the control starch as indicated by the presence of lower protein and ash contents. The starch granules were found to have irregular and disrupted surfaces after ultrasonication. The disrupted starch granules reduced the particle size and increased the swelling power of starch which was beneficial in producing a film-forming solution. The ultrasound-extracted sago starch was subsequently used to prepare a bioplastic film via solution casting method. A brownish bioplastic film with tensile strength of 0.9 ± 0.1 MPa, Young’s modulus of 22 ± 0.8 MPa, elongation at break of 13.6 ± 2.0% and water vapour permeability (WVP) of 1.11 ± 0.1 × 10⁻⁸ g m⁻¹ s⁻¹ Pa⁻¹ was obtained, suggesting its feasibility as bioplastic material. These findings provide a means of utilization for SPW which is in line with the contemporary trend towards greener and sustainable products and processes.

The Food-Materials Nexus: Next Generation Bioplastics and Advanced Materials from Agri-Food Residues

The most recent strategies available for upcycling agri-food losses and waste (FLW) into functional bioplastics and advanced materials are reviewed and the valorization of food residuals are put in perspective, adding to the water-food-energy nexus. Low value or underutilized biomass, biocolloids, water-soluble biopolymers, polymerizable monomers, and nutrients are introduced as feasible building blocks for biotechnological conversion into bioplastics. The latter are demonstrated for their incorporation in multifunctional packaging, biomedical devices, sensors, actuators, and energy conversion and storage devices, contributing to the valorization efforts within the future circular bioeconomy. Strategies are introduced to effectively synthesize, deconstruct and reassemble or engineer FLW-derived monomeric, polymeric, and colloidal building blocks. Multifunctional bioplastics are introduced considering the structural, chemical, physical as well as the accessibility of FLW precursors. Processing techniques are analyzed within the fields of polymer chemistry and physics. The prospects of FLW streams and biomass surplus, considering their availability, interactions with water and thermal stability, are critically discussed in a near-future scenario that is expected to lead to next-generation bioplastics and advanced materials.

Sonication increases the porosity of uncooked rice kernels affording softer textural properties, loss of intrinsic nutrients and increased uptake capacity during fortification

This work investigates the effect of sonication on brown and milled rice grains of both waxy and non-waxy varieties. We report herein the microstructural analysis of uncooked rice kernels under sonication and its effect on the textural properties. X-ray computed tomography results showed the formation of microporous surfaces and the creation of cracks and fissures. Sonication increased the % porosity of the rice samples allowing for easy penetration of water during the cooking process and promotes softer texture. Moreover, the effect of sonication in brown rice resulted to the decrease in endogenous iron and phosphorus contents but increased its capacity for iron uptake through fortification when sonicated rice is soaked in the mineral solution.

Optimization of Sorghum Kafirin Extraction Conditions and Identification of Potential Bioactive Peptides

The interest in extracting kafirins (KAF), the main storage protein from sorghum grain has recently increased due to its gluten-free content and the significant scientific evidence showing the health benefits of the bioactive peptides from cereal grains in human diets. The objectives were to obtain the highest percentage of KAF extraction using amyloglucosidase as pretreatment to increase the extraction yield and predict the bioactive peptides in the KAF. In this study, pretreatments with amyloglucosidase increased the extraction yield of KAF compared with extraction methods using only ethanol and sodium metabisulfite. Two protein fragment sequences were identified from KAF extract and were evaluated for potential bioactive peptide using the BIOPEP-UWM database, which suggest that KAF proteins from white sorghum may be considered as good precursors of dipeptidyl peptidase-inhibitor, angiotensin-converting enzyme inhibitor, antioxidant and hypotensive peptides following chymotrypsin, thermolysin, and subtilisin and their combination. Average scores aligned using PeptideRanker confirmed KAF proteins' potential sources of bioactive peptides with over 5 peptides scored over 0.8. In addition, 31 unexplored peptide sequences that could have biological activity were identified. Our results suggest that KAF can be used in the peptide productions with potential biological activity and beyond.

Extraction of high-amylose starch from Radix Puerariae using high-intensity low-frequency ultrasound

High-amylose starch is in great demand in the food industry due to its unique functional properties but has very limited source. In this study, high-amylose starch was successfully extracted from Radix Puerariae using ultrasound extraction. The effects of ultrasound intensity (15.29, 20.38, 22.93, 24.46 and 25.38 kW/m²) and frequency (20 and 45 kHz) on extraction kinetics, and chemical compositions, crystallinity, in vitro digestion behaviour and gelling properties of starches were investigated. It was shown that with the increasing intensity, the extraction rate and content of amylose increased, but for starch the extraction rate increased initially until reached a plateau at an intensity of 24.46 kW/m². With the increasing low-frequency, the extraction rate and content of amylose increased, but the extraction rate of starch decreased. Based on statistical tests, the Logistic model was found to fit well to the extraction kinetics of amylose, and the Peleg model fit well to that of starch. The extraction yield of starch was not significantly affected by ultrasound conditions. The obtained starch has a high-purity with a content of more than 99% dry basis and an unchanged crystallinity. Moreover, the increased amylose content resulted in an increase of the content of slowly digestible starch, resistant starch, and gelling hardness. This study demonstrates that high-amylose starch can be obtained using ultrasound extraction from Radix Puerariae at high-intensity low-frequency.

Development of a 96-well plate iodine binding assay for amylose content determination

Cereal starch amylose/amylopectin (AM/AP) is critical in functional properties for food and industrial applications. Conventional methods of AM/AP are time consuming and labor intensive making it difficult to screen the large sample sets necessary for evaluating breeding samples and investigating environmental impact on starch development. The objective was to adapt and optimize the iodine binding assay in a 96-well plate format for measurement at both λ 620 nm and λ 510 nm. The standard curve for amylose content was scaled to a 96-well plate format and demonstrated R(2) values of 0.999 and 0.993 for single and dual wavelengths, respectively. The plate methods were applicable over large ranges of amylose contents: high amylose maize starch at 61.7±2.3%, normal wheat starch at 29.0±0.74%, and a waxy maize starch at 1.2±0.9%. The method exhibited slightly greater amylose content values than the Concanavalin A method for normal type starches; but is consistent with cuvette scale iodine binding assays.

Effect of nitrogen fertilization and cover cropping systems on sorghum grain characteristics

Cover crop treatments and nitrogen (N) fertilization rates were investigated for their impact on sorghum grain quality attributes. Sorghum was planted in field plots treated with differing cover cropping systems and fertilization rates. The size (weight and diameter) and hardness of the kernels were influenced by both the cover crop and N rates. The protein content increased as the N rate increased and also with the addition of cover crops to the system. The protein digestibility values and starch granule size distributions were not affected by N rate or the cover cropping treatments. Soil properties were tested to determine relationships with grain quality attributes. The utilization of cover crops appears to increase the protein content without causing a deleterious effect on protein digestibility. The end-product quality is not hampered by the use of beneficial cropping systems necessary for sustainable agriculture.

Sorghum proteins: the concentration, isolation, modification, and food applications of kafirins

Celiac disease is a serious condition affecting millions of individuals. Those afflicted with this illness are resigned to a lifelong avoidance of products containing the storage prolamin proteins found in cereal grains wheat, rye, and barley. Since many food products are based on these cereals, especially wheat, celiac patients have very limited food choices, and those that are available to them are generally poor in quality, often nutritionally deficient, and expensive. Furthermore, this condition also indirectly affects their families and friends with whom they share meals. Thus, a burgeoning need exists to develop nutritious, palatable, and affordable foods, especially staples like bread and pasta, for these individuals and their families and friends who are accustomed to wheat based products. Grain sorghum and its proteins are safe for celiac patients and individuals with varying levels of gluten intolerances. However, the main sorghum proteins, kafirins, are resistant to digestion. They are also difficult to extract and modify in an industrial-scale process and with food-compatible chemicals, thus limiting their use in foods. This review describes studies on kafirin extraction and methods for modifying sorghum proteins for improved nutrition and functionality, as well as food applications. Armed with this knowledge, scientists and technologists will be in a better position to identify opportunities that will further enhance the nutritional and functional value of sorghum proteins.

Fractionation of hairless canary seed (Phalaris canariensis) into starch, protein, and oil

Canary seed is an important specialty crop in Canada. The current market for this true cereal (i.e., belonging to the family Poaceae as wheat) is limited to feed for caged birds. However, canary seed holds a promise for many food and industrial applications based on its composition. Three wet milling procedures based on ethanol (E), water (W), and alkaline (A) extractions used in different order were investigated to determine extraction efficiency and purity of starch, protein, oil, and fiber separated from hairless canary seed, a variety developed for human consumption. Highest extraction efficiencies were obtained when canary seed was defatted with ethanol and then extracted with alkali and water (EAW process). Using this process, approximately 92% pure starch, 75% pure protein, and oil were recovered from canary seed groats. The highest purity of protein, however, was obtained when canary seed was fractionated by the EWA process, that is, defatted and then extracted with water followed by alkali. Fiber component separated prior to alkaline extraction contained high amounts of nonfiber components as indicated by its yield. The EAW extraction process seems to be more promising in canary seed fractionation based on recovery and purity of components.

Vessel wall vibrations: trigger for embolism repair?

Xylem embolism repair is preceded by starch depolymerisation in vessel-associated cells (VAC) of Laurus nobilis L. (laurel) twigs, but the primary signal triggering such a process is still unknown. We tested the hypothesis that conduit wall vibrations during cavitation may be sensed by VAC inducing starch-to-sugar conversion. Twigs of laurel from watered or stressed plants were exposed to ultrasound for 60 min to simulate acoustic waves emitted by cavitating conduits. Preliminary tests showed that ultrasound caused no damage to cell membrane integrity nor did they cause xylem embolism. The number of VAC with high starch content (HSC-cells) was estimated microscopically by counting the cells with more than 50% of their lumen filled with starch granules. Sonication had no effect on HSC-cells in twigs from watered plants while it induced a drop in the percentage HSC-cells from 80 to 40% in twigs from stressed plants, at the ultrasound source location. No effect was recorded in these twigs 20 mm from the ultrasound source. Sonication was a good simulator of cavitation in inducing starch depolymerisation which suggests a possible bio- physical nature for the signal initiating embolism repair.