Effects of Reheating Methods on Rheological and Textural Characteristics of Rice Starch with Different Gelatinization Degrees

An overview on the dry heat treatment (DHT) for starch modification: Current progress and prospective applications

Starch plays a pivotal role in numerous applications, making the enhancement of its functionality through physical processes increasingly important. Dry heat treatment (DHT) is a straightforward and eco-friendly technique that significantly improves starch characteristics and boosts food quality. This method has emerged as a focal point in starch modification research in recent years. This paper reviews current studies on the DHT of starches from various botanical sources, presenting key concepts and methodologies while delving into the impacts and mechanisms of DHT on the structural and physicochemical properties of starches. Furthermore, it elaborates on how additional components, such as ionic gums, amino acids, and sugars, can enhance the functionality of starches modified by DHT. Additionally, this review discusses the practical applications of dry heat-modified starches in the food industry, aiming to offer valuable insights for ongoing research and potential applications in enhancing food quality and functionality through innovative starch modifications.

Glutinous rice gel as all-natural ink supply for extrusion-based food 3D printing - the chemical basis of gel printability

In this study, four varieties of glutinous rice were screened out of 18 varieties as representative model inks. Gel prepared using variety WN9612 of high amylose content displayed high viscosity and large overall print deviation (OPD = 17.4 ± 0.4 %) due to difficulties in extrusion. Printed item by variety 19415 of medium amylose content showed good printability (OPD = 4.4 ± 0.4 %) and highest hardness (197.5 ± 7.3 N). Similarly good printability was demonstrated by variety 19416 (OPD = 4.1 ± 0.2 %) containing low amylose content but abundant protein and bound-water. Variety WN9446 lacking protein and moisture created item with fluid structure, lowest gel strength (738.5 ± 20.9 Pa) and standing ability. Therefore, low to medium amylose content rendered suitable viscosity, extrudability and printability of rice gel while non-starchy components predominated water mobility and texture of 3D printed items. This study for the first time establishes theoretical groundwork of selecting glutinous rice varieties with appropriate chemical composition as all-natural materials in 3D printing and food customization.

Morphological, physicochemical, and pasting properties of pre-gelatinized starch prepared by high-pressure homogenizer: A comparative study on starches from different resources

Pre-gelatinized starch, a physically modified starch known for its ability to swell in cold water, has wide applications across various industries. This study assesses the feasibility of high-pressure homogenization (HPH) in producing pre-gelatinized starches and compares their morphological, physicochemical, and pasting properties from different sources. Starches from eleven sources, including mung bean, pea, wheat, sweet potato, cassava, corn, non-waxy rice, waxy rice, chickpea, lentil, and chestnut, were processed using HPH at 150 MPa for three cycles. The resulting pre-gelatinized starch granules exhibited disrupted surface structures, increased water absorption and solubility, decreased crystallinity, and altered gelatinization temperatures. Results showed that waxy rice pre-gelatinized starch had the highest degree of pre-gelatinization (90.27%) and water absorption index (61.95%), while chestnut pre-gelatinized starch had the highest water solubility index (21.58%) and lentil pre-gelatinized starch demonstrated the highest gel strength (2178.00 g). X-ray diffraction analysis revealed a significant reduction in crystallinity, with values ranging from 13.96% to 18.29%. Additionally, the study observed variations in pasting properties, with cassava pre-gelatinized starch exhibiting the highest peak viscosity (5458 cP), trough viscosity (3864 cP), and final viscosity (6536 cP). These findings indicate that HPH is an effective method for producing pre-gelatinized starch with enhanced functional properties, enriching the scientific understanding of pre-gelatinized starches from different sources and promoting their application in the food industry and other sectors.

Three nonconventional starch: Comparison of physicochemical properties and in vitro digestibility

Extraction of starch from waste is also an effective way to recover resources and provide new sources of starch. In this study, starch was isolated from white kidney bean residue, chickpea residue, and tiger nut meal after protein or oil extraction, and the morphology of starch particles was observed to determine their physicochemical properties and in vitro digestibility. All these isolated starches had unique properties, among which white kidney bean starch (KBS) had a high amylose content (43.48%), and its structure was better ordered. Scanning electron microscopy revealed distinct granular morphologies for the three starches. KBS and chickpea starch (CHS) were medium-granular starches, whereas tiger nut starch was a small granular starch. Fourier transform infrared spectroscopy analysis confirmed the absence of significant differences in functional groups and chemical bonds among the three starch molecules. In vitro digestibility studies showed that CHS is more resistant to enzymatic degradation. Overall, these results will facilitate the development of products based on the separation of nonconventional starches from waste.

Research on rice starch gel preparation and crosslink network structure-rheological property based on direct-writing 3D printing

Amylopectin and amylose components are natural polymers within rice starch granules, intertwined in specific conditions to form gel polymerized with pore crosslink network, has potential printing properties. In this study, a rice starch gel preparation scheme is proposed for stable properties, and starch granule phase transition mechanism is analyzed based on RVA test during preparation, it can be divided into four-stage, swelling, reacting, homogenizing and self-assembling stages. Gel surface tension and contact angle tested with starch concentration effect, a correlation is developed, reflecting a competition result to gel droplet macro-morphology between the intermolecular cohesion and crosslink network. SEM is used to reveal typical crosslink structures of different starch molecular component proportions, providing objective support for starch gel rheologic property change. Results indicate gel interior crosslink network formed under concentration 12 %, the gel with amylose 4.475 % presents better printing accuracy. Gel shear modulus positively correlated with amylose proportion. Japonica gel under 20 % is of higher viscosity and rapid reassembly ability after interior crosslink network is broken. Max dynamic viscosity is positively correlated with starch concentration. The study aims to provide theoretical and practical support for in-depth analysis of rice starch material application in direct-write 3D printing.