Changes of starch during thermal processing of foods: Current status and future directions

Control of the oil content of fried dough sticks through modulating structure change by reconstituted gluten fractions

In our study, we explored how gluten's role during dough formation and thermal processing can mitigate the adverse effects of physical factors on product quality. We discovered that a gluten network with a gliadin/glutenin ratio of 5:5 effectively limits oil penetration into the dough's core. This particular ratio is found to reduce the exposure of hydrophobic groups due to the presence of hydrated β-sheet structures. In contrast, gluten networks with higher gliadin proportions than typical wheat gluten tend to be looser, leading to increased chromophore exposure and facilitating more oil absorption. These observations highlighted the complex link between changes in gluten structure, varying protein compositions, and oil content in fried dough sticks. This research provided a foundation for developing specialized low-fat wheat flour and improving the quality of fried dough products.

Enhanced B-type starch granules proportion modulates starch-gluten interactions during the thermal processing of reconstituted doughs

This work investigated structure-properties changes of reconstituted wheat A/B starch doughs under different ratios during dynamic thermal processing. Results indicated that a change in spatial conformation and aggregation structure of the starch-gluten system was induced with heating (30 °C-86 °C). Moderately increased B starch ratio can effectively fill the gluten network and improve starch-protein interactions, which promotes the free sulfhydryl group oxidation and results in the formation of more glutenin macropolymer; this contributes to a higher degree of cross-linking and stability to the gluten network matrix. This improvement is enhanced as the heating temperature is increased. Notably, the B starch ratio requires to be controlled within a suitable range (≤ 75%) to avoid aggregation and accumulation on the gluten matrix triggered by its excess. This work may provide insights and optimization for clarifying the on-demand regulation strategy of A/B starch in dough processing.

Effects of heat treatment at different moisture of mung bean flour on the structural, gelation and in vitro digestive properties of starch

Effects of heat treatment (100 °C) at different moisture content (13-70 %) on the structural, gelation and digestive properties of starch in real mung bean flour (MBF) systems are investigated. The results showed that the structural destruction of the starch, the starch-lipid complexion and starch-protein interaction were promoted with increasing moisture content. The starch-protein interaction was mainly driven by hydrophobic interaction forces, leading the increase of total phase transition enthalpy. Even though starch retained ordered structure after heating at 50 %-70 % moisture, the typical pasting curve almost disappeared. The less leached amylose to construct the continuous phase, and more flexible amylopectin swollen granules dispersed in the matrix may weakened the viscoelasticity of the gels. As a result, two distinct gel textures were presented: soft solids with good water-binding capacity (below 30 %) and pasty fluids (above 40 %). Starch-lipid/protein interactions were demonstrated to retard the digestion rate of starch during MBS gelatinization according to the two-stage first-order kinetic and LOS (logarithm of the slope) models.

New insights into how freeze-drying and cryo-milling affects the fine structure and digestibility of gelatinized starch

Freeze-drying (FD) and cryo-milling (CM) are common methods for preparing powder gelatinized starch samples. This study investigates the structural characterization of raw/gelatinized maize starches and digestibility after FD/CM processes to elucidate their effect on starch digestibility determination. Results showed that FD slightly increased digestibility, while higher initial glucose content in CM samples, especially for gelatinized samples. Only FD retained the granular morphology and relative crystallinity (RC), while gelatinized-FD decreased RC by 75%. CM decreased RC by 12%, while gelatinized-CM decreased it by 97%. Combined with short-range and chain structural results, FD tended to disrupt internal connected chains through volume stress, while CM cleaved glycosidic bonds in external chain. Stretched chains in gelatinized starch promoted the breakage of chains during shearing and their efficient binding with digestive enzymes. These findings would provide a basis for pre-treatment of powder samples and processes of starch- rich foods.

Comparative study on the structure characterization and activity of RS5 made from Canna edulis native starch and high-amylose corn starch

In this study, the high amylose corn starch and Canna edulis native starch were compounded with lauric acid and fermented by human fecal inoculation in vitro. Changes in beneficial metabolite profile and microbiota composition were evaluated. The structural properties showed that both NS-12C and HAMS-12C formed V-shaped crystals under the same preparation method, but NS-12C had a higher composite index and resistance content than HAMS-12C. At the end of fermentation, the starch-lauric acid complexes prepared from the two types of starch significantly promoted the formation of short-chain fatty acids and the contents of acetic acid, butyric acid and valeric acid produced by NS-12C were higher than those of HAMS-12C(p>0.05). HAMS-12C and NS-12C both increased the relative abundance of Blautia. Notably, NS-12C also increased the relative abundance of beneficial bacteria Bifidobacterium and Meganomas, while HAMS-12C did not. These results suggested that this effect may be related to starch type and provide a basis for designing and producing functional foods to improve intestinal health in Canna edulis native starch.

Dynamic rheological behavior of high-amylose wheat dough during various heating stages: Insight from its starch characteristics

The objective of this study was to understand how the dynamic rheological behaviors of high-amylose wheat (HAW) dough during various heating stages measured using a mixolab were affected by the starch properties. At the heating stage of 30 °C - 90 °C, low minimum (C2) and peak (C3) torques were observed for HAW doughs, which resulted from their reduced starch granule swelling. During holding at 90 °C, HAW doughs had low minimum (C4) and C3 - C4 torques, indicating a good resistance to mechanical shear and endogenous enzyme degradation. HAW doughs also had low final (C5) and setback (C5 - C4) torques, consistent with their low starch swelling power and solubility. The increased amylose in HAW starch formed long-chain double-helical B-type polymorph and amylose-lipid complex, which resulted in high starch gelatinization-temperatures and enthalpy change, low swelling power and solubility, low pasting viscosity, and high resistance of swollen granules to mechanical shear and enzyme degradation. The overall patterns of dough-rheological behavior of HAW doughs during heating were similar to their respective starch pasting profiles, indicating that starch was the dominant contributor to the dough rheology during heating. This study provides useful information for food applications and manufacturing of HAW-based products, especially none-fermented products requiring firm texture and low viscosity.

Insights into Grain Milling and Fractionation Practices for Improved Food Sustainability with Emphasis on Wheat and Peas

Cereal grains and pulses are staple foods worldwide, being the primary supply of energy, protein, and fiber in human diets. The current practice of milling and fractionation yields large quantities of byproducts and waste, which are largely downgraded and end up as animal feeds or fertilizers. This adversely affects food security and the environment, and definitely implies an urgent need for a sustainable grain processing system to rectify the current issues, particularly the management of waste and excessive use of water and energy. The current review intends to discuss the limitations and flaws of the existing practice of grain milling and fractionation, along with potential solutions to make it more sustainable, with an emphasis on wheat and peas as common fractionation crops. This review discusses a proposed sustainable grain processing system for the fractionation of wheat or peas into flour, protein, starch, and value-added components. The proposed system is a hybrid model that combines dry and wet fractionation processes in conjunction with the implementation of three principles, namely, integration, recycling, and upcycling, to improve component separation efficiency and value addition and minimize grain milling waste. The three principles are critical in making grain processing more efficient in terms of the management of waste and resources. Overall, this review provides potential solutions for how to make the grain processing system more sustainable.

Rheological, thermal, and in vitro starch digestibility properties of oat starch-lipid complexes

The influence of oat lipids on the structural, thermal, rheological, and in vitro digestibility properties of oat starch under heat processing conditions was investigated. X-ray diffraction, fourier infrared spectroscopy, and differential scanning calorimetry revealed the formation of a V-shaped crystal structure between starch and lipid, resulting in enhanced orderliness and enthalpy. Oat lipids decreased the final viscosity and gel strength of oat starch while weakening the trend towards gel network formation. Additionally, oat lipids exhibited enhanced resistance to starch hydrolase, leading to elevated contents of slowly digestible starch and resistant starch. Consequently, this leads to an augmentation in the rate constants for the rapid digestion fraction (k1) and the slow digestion fraction (k2). When the lipid content reached 7.50 %, a significant increase of 42.20 % was observed in the maximum digestibility of slow digestion fraction (C∞2), while a notable decrease of 44.06 % was noted in the maximum digestibility of rapid digestion fraction (C∞1). The correlation analysis revealed that lipid content, final viscosity, and enthalpy exerted significant influences on in vitro starch digestion. These results demonstrate the substantial impact of lipid content on oat starch structure, subsequently affecting its thermal, rheological, and digestive properties.

Effect of radio frequency explosion puffing on physicochemical, functional and crystalline properties, and in vitro digestibility of yam flour

Yam flour was modified by radio frequency explosion puffing at different moisture content, puffing temperature, and puffing pressure difference. After puffing, the protein content and lipid content increased by 0.56-1.28 % and 0.23-0.39 %, respectively. Puffing caused the flour granules to aggregate, increasing the thermal transition temperatures and reducing the pasting viscosities, enthalpy, 1047/1022 cm-1 ratio, and relative crystallinity. Puffing reduced the intensity of the infrared spectrum peak at 1641 cm-1 by breaking the hydrogen bonds without changing A-type crystalline structure. Puffing promoted the conversion of random-coil and α-helix protein structure to β-turn and β-sheet. Puffing retarded in vitro digestibility by reducing rapidly digestible starch content by 7.04-11.12 % and rising slowly digestible starch content and resistant starch content by 4.02-4.89 % and 2.77-3.10 %, respectively. Radio frequency explosion puffing altered flour's physicochemical, functional and digestibility properties by destroying the protein structure and promoting the interaction of starch and proteins/lipids.

Understanding the gut microbiota by considering human evolution: a story of fire, cereals, cooking, molecular ingenuity, and functional cooperation

SUMMARYThe microbial community inhabiting the human colon, referred to as the gut microbiota, is mostly composed of bacterial species that, through extensive metabolic networking, degrade and ferment components of food and human secretions. The taxonomic composition of the microbiota has been extensively investigated in metagenomic studies that have also revealed details of molecular processes by which common components of the human diet are metabolized by specific members of the microbiota. Most studies of the gut microbiota aim to detect deviations in microbiota composition in patients relative to controls in the hope of showing that some diseases and conditions are due to or exacerbated by alterations to the gut microbiota. The aim of this review is to consider the gut microbiota in relation to the evolution of Homo sapiens which was heavily influenced by the consumption of a nutrient-dense non-arboreal diet, limited gut storage capacity, and acquisition of skills relating to mastering fire, cooking, and cultivation of cereal crops. The review delves into the past to gain an appreciation of what is important in the present. A holistic view of "healthy" microbiota function is proposed based on the evolutionary pathway shared by humans and gut microbes.

Effects of oil and heating on the physicochemical and microstructural properties of gluten-starch dough

Oil has crucial applications for improving the quality of some wheat products during dough formation and heat-processing. Herein, the influence of oil modification and thermal-mechanical treatment on dough prepared mainly with wheat starch and gluten was investigated. Oils with different structures addition reduced the hardness but improved the tensile strength of dough and inhibited starch retrogradation. Oil also reduced the disulfide bond, hydrogen bond and hydrophobic interactions whilst changed the rheology of dough. The X-ray diffraction patterns were characterised by new weak peaks at approximately 12.9°, and 19.8°, indicating that thermal-mechanical treatment promoted the formation of V-type complexes. Oil modification impaired dough short-range ordered structure, but prevented part starch granule crystallinity degradation caused by thermal-mechanical treatment. Scanning electron microscopy revealed oil modification and thermal-mechanical treatment synergistically affected starch-gluten agglomeration. Our findings contributed to elucidate the influence of oil modification and thermal-mechanical treatment on dough functionality.

The influence of short-range molecular order in gelatinized starch on the formation of starch-lauric acid complexes

A model system of gelatinized wheat starch (GWS) and lauric acid (LA) was used to examine the effect of residual short-range molecular order in GWS on the formation of starch-lipid complexes. The extent of residual short-range molecular order, as determined by Raman spectroscopy, decreased with increasing water content or heating duration of gelatinization. The enthalpy changes, crystallinity, short-range molecular order and the in vitro enzymic digestion of GWS-LA complexes increased initially to a maximum and then declined as the short-range molecular order in GWS decreased, showing that there was an optimal amount of residual short-range molecular order in GWS for maximizing GWS-LA complexes formation. Below this optimum amount, the limited disruption of short-range molecular order may constrain the mobility of amylose chains for complexation with LA, whereas with excessive disruption above this amount the amylose chains may be too disorganized or entangled to form complexes with LA. The susceptibility of GWS-LA complexes to enzymatic hydrolysis was influenced by both long- and short-range structural order, and to a lesser extent the amounts of complexes. This study showed clearly the role of short-range molecular order in gelatinized starch in influencing the formation of GWS-LA complexes.

Gallic acid forms V-amylose complex structure with starch through hydrophobic interaction

This study aimed to investigate the role of amylose and amylopectin in the formation of starch-polyphenol complex and elucidate the interaction mechanisms. Gallic acid (GA) was used to complex with maize starch with various amylose contents. Results showed GA formed V-type crystals with normal maize starch (NMS) and high amylose maize starch (HAMS), while higher relative crystallinity was exhibited in HAMS-GA complexes than NMS counterparts. Molecular structure analysis revealed more amylose in GA-starch complexes than in treated starch counterparts without GA, and this was more apparent in HAMS than NMS, implying amylose is preferred to complex with GA than amylopectin. FTIR detected higher R1047/1022 value in starch-GA complexes than their starch counterparts without GA, suggesting increased short-range ordered structrure of complexes. Typical signatures of hydrophobic interactions were further revealed by isothermal titration calorimetry, indicating the complexation of GA to starch is mainly through hydrophobic bonds. More binding sites were observed for HAMS (72.50) than NMS (11.33), which proves the preferences of amylose to bind with GA. Molecular dynamics simulated the complexation of GA to amylose, and confirmed hydrophobic bond is the main interaction force. These findings would provide guidance for precise design and utilization of starch-polyphenol complexes in functional foods.

Sustainable papaya plant waste and green tea residue composite films integrated with starch and gelatin for active food packaging applications

This study explores the sustainable utilization of wastes from a papaya plant (papaya peels (PP), papaya seeds (PS), leaf-stem (PL)) and dried green tea residues (GTR) for the synthesis of bioplastics. The dried GTR were individually blended with each papaya waste extract and then boiled in water to get three composite papaya plant waste-green tea supernatants. Potato starch and gelatin-based functional films were prepared by integrating each with the composite papaya waste-green tea supernatant liquid. This work introduces a dissolved organic matter (DOM) study to the field of bioplastics, with the goal of identifying the organic components and macromolecules inherent in the PW supernatants. When compared with the films prepared solely from papaya waste (PW) supernatants, PW-GTR composite supernatant films prevent UV light transmission with superior antioxidant and mechanical properties. Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction spectroscopy (XRD), and atomic force microscopy (AFM) were utilized to characterize the starch and gelatin PW-GTR films. Owing to the exceptional antioxidant, UV barrier, and remarkable biodegradable properties of the starch/PW/GTR and gelatin/PW/GTR composite films, make them ideal for use in food packaging applications.

Mechanism of feed moisture levels in extrusion treatment to improve the instant properties of Chinese yam (Dioscorea opposita Thunb.) flour

Extruded yam flour was prepared at different feed moisture to improve its instant properties. The water solubility index (WSI) and water absorption index (WAI) were used to compare the instant properties of yam flour. Their chemical compositions, particle size distribution, crystalline structure, and microscopic forms were also analyzed to assess the effects of feed moisture on the instant properties of yam flour. We found that extrusion significantly improved the instant properties of yam flour, while the WSI value increased from 29.50% to 71.86% and the WAI value decreased from 387.88% to 228.06% with decreased feed moisture. Extrusion led to the degradation of total starch and amylopectin, and the contents of soluble substances increased markedly. Extrusion destroyed the granular and crystalline structures, which were reconstituted as amylose-lipid complexes with a significant decrease in relative crystallinity. Increasing the feed moisture was beneficial to the flow and color retention, while lower feed moisture was more favorable to enhance the instant properties.

Production and characterization of starch-lignin based materials: A review

In their pristine state, starch and lignin are abundant and inexpensive natural polymers frequently considered green alternatives to oil-based and synthetic polymers. Despite their availability and owing to their physicochemical properties; starch and lignin are not often utilized in their pristine forms for high-performance applications. Generally, chemical and physical modifications transform them into starch- and lignin-based materials with broadened properties and functionality. In the last decade, the combination of starch and lignin for producing reinforced materials has gained significant attention. The reinforcing of starch matrices with lignin has received primary focus because of the enhanced water sensitivity, UV protection, and mechanical and thermal resistance that lignin introduces to starch-based materials. This review paper aims to assess starch-lignin materials' production and characterization technologies, highlighting their physicochemical properties, outcomes, challenges, and opportunities. First, this paper describes the current status, sources, and chemical modifications of lignin and starch. Next, the discussion is oriented toward starch-lignin materials and their production approaches, such as blends, composites, plasticized/crosslinked films, and coupled polymers. Special attention is given to the characterization methods of starch-lignin materials, focusing on their advantages, disadvantages, and expected outcomes. Finally, the challenges, opportunities, and future perspectives in developing starch-lignin materials, such as adhesives, coatings, films, and controlled delivery systems, are discussed.

Improving rice eating and cooking quality by enhancing endogenous expression of a nitrogen-dependent floral regulator

Improving rice eating and cooking quality (ECQ) is one of the primary tasks in rice production to meet the rising demands of consumers. However, improving grain ECQ without compromising yield faces a great challenge under varied nitrogen (N) supplies. Here, we report the approach to upgrade rice ECQ by native promoter-controlled high expression of a key N-dependent floral and circadian clock regulator Nhd1. The amplification of endogenous Nhd1 abundance alters rice heading date but does not affect the entire length of growth duration, N use efficiency and grain yield under both low and sufficient N conditions. Enhanced expression of Nhd1 reduces amylose content, pasting temperature and protein content while increasing gel consistence in grains. Metabolome and transcriptome analyses revealed that increased expression of Nhd1 mainly regulates the metabolism of carbohydrates and amino acids in the grain filling stage. Moreover, expression level of Nhd1 shows a positive relationship with grain ECQ in some local main cultivars. Thus, intensifying endogenous abundance of Nhd1 is a promising strategy to upgrade grain ECQ in rice production.

Native and modified starches from underutilized seeds: Characteristics, functional properties and potential applications

Seeds represent a potential source of starch, containing at least 60-70% of total starch, however many of them are treated as waste and are usually discarded. The review aim was to analyze the characteristics, functional properties, and potential applications of native and modified starches from underutilized seeds such as Sorghum bicolor L. Moench (WSS), Chenopodium quinoa, Wild. (QSS), Mangifera indica L. (MSS), Persea americana Mill. (ASS), Pouteria campechiana (Kunth) Baehni (PCSS), and Brosimum alicastrum Sw. (RSS). A systematic review of scientific literature was carried out from 2014 to date. Starch from seeds had yields above 30%. ASS had the higher amylose content and ASS and RSS showed the highest values in water absorption capacity and swelling power, contrary to MSS and PCSS while higher thermal resistance, paste stability, and a lower tendency to retrograde were observed in MSS and RSS. Functional properties such as water solubility, swelling power, thermal stability, low retrogradation tendency, and emulsion stability were increased in RSS, WSS, QSS, and MSS with chemical modifications (Oxidation, Oxidation-Crosslinking, OSA, DDSA, and NSA) and physical methods (HMT and dry-heat). Digestibility in vitro showed that WSS and QSS presented high SDS fraction, while ASS, MSS, PCSS, and HMT-QSS presented the highest RS content. Native or modified underutilized seed starches represent an alternative and sustainable source of non-conventional starch with potential applications in the food industry and for the development of healthy foods or for special nutritional requirements.

Variation in structural and in vitro starch digestion of pulse cotyledon cells imposed by temperature-pressure-moisture combinations

Starch digestibility in whole pulses is affected by food structural characteristics, which in turn can be modulated by processing methods. In present study, high-pressure steam (HPS) and hydrothermal treatment (HT) with different moisture content were applied to clarify the mechanisms of processing variables affecting in vitro starch digestibility in pulse cells. Based on thermal and X-ray results, the relative crystallinity of cells decreased after HPS and HT treatments. However, HPS-treated cells under higher (>50%) moisture content showed insignificant discrepancies in crystallinity than HT samples. Starch digestion in HPS-treated cells increased with higher moisture content but was still lower than in HT samples. Results of FITC-dextran diffusion and methyl esterification of cell walls indicated that cells with higher wall permeability exhibited relatively higher starch digestibility. This study suggests that the enzyme susceptibility to starch in cells is dominantly influenced by cell wall structure, which could be optimized through processing variables.

Effect of heat-moisture treatment on the physicochemical properties and digestibility of proso millet flour and starch

Proso millet flour (PMF) and starch (PMS) were subjected to heat-moisture treatment (HMT) at 25 % moisture content and 110 °C for 4 h. The effects of HMT on physicochemical and structural properties and in vitro digestibility of PMF and PMS were analyzed. After HMT, SEM showed aggregation and damage to the surface of starch granules, while CLSM showed proteins wrapped around the granules. The amylopectin chain length distribution (CLD) remained unchanged in PMF and PMS after HMT, indicating intact covalent bonds between glucose units. HMT decreased the swelling power, solubility, viscosity of the paste, and gelatinization enthalpy and increased the pasting temperature and gelatinization temperature of PMF and PMS. HMT changed the XRD pattern of PMF from A to A + V type starches, whereas that of PMS remained unchanged. FTIR study showed an increase in the degree of short-range molecular order of PMF and PMS after HMT. In vitro digestibility evaluation showed that the rapidly (RDS) and slowly digestible starch (SDS) contents of PMF and PMS increased, whereas the resistant starch (RS) content decreased after HMT. HMT flour and starch have suitable properties for use in a wide range of food products, from canned to frozen, as well as non-food products.

Insight into the Effects of Drying Methods on Lanzhou Lily Rehydration

This study investigated the effects of drying methods (hot air drying (HAD), microwave vacuum drying (MVD), and vacuum freeze drying (VFD)) on the rehydration performance (RP) of dried Lanzhou lily scales (LLS). Rehydration rate and water migration showed that MVD had the best RP, followed by VFD, while HAD had the worst. The results of additional morphology observation using scanning electron microscopy (SEM) and micro X-ray computed tomography (CT) imaging showed that both MVD and VFD created more channels in more porous structures, which facilitated their better RP than that by HAD. The results also revealed the spatial structure diversity (including pores, channels size, and internal network) of each dried Lanzhou lily scale group. In addition, studies analyzed how drying techniques affected the physiochemical properties of lily starch, including its water solubility, pasting profiles, and starch particle morphology. The findings indicated that when MVD was in operation, partial gelatinization in lily starch was brought about by thermal effects, allowing MVDS crystals to change from B-type to V-type and causing MVDS to have better water absorption ability. Consequently, despite the fact that MVD's desiccated lilies have a lower porous structure and thinner channels than VFD's, MVD has a higher RP than VFD.

Effects of cereal grain cell wall composition and structure on starch digestion

BACKGROUND

Wheat is an important food crop, and its characteristics vary depending on the region of cultivation; different environments have varying effects on the composition of the grains. We previously reported the effects of environmental factors on wheat grain cell wall composition and structure.

METHODS

The variations in the structure of aleurone cell walls between different wheat samples were examined to determine the effects of aleurone cell walls on grain starch digestion properties. Ten different varieties of wheat grains with different aleurone cell wall structure and composition constituted a simple research system used to study their effect on the starch digestion of bread.

RESULTS

The aleurone cell wall thickness ranged from 3.05 μm to 4.67 μm, and the arabinose to xylose ration of water-extractable arabinoxylan was 0.79-0.97. With the increase in arabinoxylans content or cell wall thickness, the total digestibility of starch within the bread decreased; this phenomenon may be related to the changes in the interaction between polysaccharides and starch granules in this process.

CONCLUSION

Our study showed that the wheat cell wall structure has a great impact on starch hydrolysis, indicating that the change in the digestibility of starch in flour and bread may be due to changes in the cell wall structure leading to different combinations, thus affecting digestibility. The present study showed that the cell wall combines the starch granules during the bread-making process; thus, the diffusion of enzymes through the cell wall was hindered. This article is protected by copyright. All rights reserved.

Novel Approach for Quantitative Characterization of Short-Range Molecular Order in Gelatinized Starch by X-ray Diffraction

A novel quantitative method was developed to characterize short-range molecular order in gelatinized wheat and potato starches using X-ray diffraction (XRD). Gelatinized starches with different amounts of short-range molecular order and amorphous starches with no short-range molecular order were prepared and characterized by the intensity and area of Raman spectral bands. The degree of short-range molecular order in the gelatinized wheat and potato starches decreased with increasing water content used for gelatinization. By comparing XRD patterns of gelatinized and amorphous starch, the XRD peak at 33° (2θ) was shown to be typical of gelatinized starch. The relative peak area (RPA), intensity, and full width at half-maximum (FWHM) of the XRD peak at 33° (2θ) decreased with the increase in water content for gelatinization. We propose that the RPA of the XRD peak at 33° (2θ) can be used to quantify the amount of short-range molecular order in gelatinized starch. The method developed in this study will help to explore and understand the relationship between the structure and functionality of gelatinized starch in food and nonfood applications.

Effect of Cooking Method and Enzymatic Treatment on the in vitro Digestibility of Cooked and Instant Chestnut Flour

Microwave treatment, roasting, boiling, and enzymatic treatment were used to prepare cooked and instant chestnut flour, and the in vitro digestibility were compared. Cooking gelatinized the starch and destroyed the granular and crystal structure, increasing starch digestibility. After enzymatic hydrolysis, starches were degraded by 20~24%, and the reducing sugar content of the instant flours increased by 79~94%. Starch digestibility was reduced after enzymatic hydrolysis, however, the estimated glycemic index (GI) increased to 65.1 ~ 77.7 due to the combined effect of increased reducing sugar and decreased starch hydrolysis in the instant flours. The chestnuts treated by 'boiling + enzymes' are still a medium GI food. These findings give guidance for the development of low GI cooked and instant chestnut flour.

Influence of ultrasonic-microwave power on the structure and in vitro digestibility of lotus seed starch-glycerin monostearin complexes after retrogradation

The digestibility of starches with high amylose content can be modulated by the complexation with lipids, which is largely influenced by physical modification methods. In the current work, the impact of ultrasound-microwavre synergistic treatment on the structure and in vitro digestibility of lotus seed starch-glycerin monostearin complexes (LS-GMSc) after retrogradation were investigated. Results showed that 400 W of ultrasound treatment combined with microwave was more conducive to the formation of LS-GMSc, which increased the microcrystalline region and ordering degree of starch. However, excessively high ultrasound intensity weakened V-type diffraction and promoted amylose recrystallization. Investigation of the micromorphology and thermal properties revealed that the existence of V-complexes retarded starch retrogradation, and this effect was significantly enhanced after appropriate ultrasound (400 W) treatment. The digestion showed that 400 W of ultrasound treatment improved the digestive resistance of starch complexes and increased the content of resistant starch. These results are significant to the theoretical foundation and functional application of V-type complexes on anti-gelling and anti-digestion.

Effect of adding vegetable oils to starches from different botanical origins on physicochemical and digestive properties and amylose-lipid complex formation

Coconut oil, rice bran oil and sunflower oil were added to rice, corn, banana and mung bean starches and the effect on physicochemical properties, amylose-lipid formation and digestive properties were investigated. Starch samples were heated while oil was added and starch treated without oil addition served as the control. Starches with different botanical origins complexed diversely with vegetable oils. The RDS content in corn and rice starches with oil addition decreased, while SDS and RS fractions increased. By contrast, the RS content of treated banana and mung bean starches decreased compared with native starch but RS and SDS contents increased when oil was added compared with the control sample. The A-type crystalline polymorph of corn and rice starches changed to a mixed A + V form, whereas native mung bean (C(A)-type) changed to B-pattern and banana starch remained unchanged (B-type). FTIR spectra indicated new peaks corresponding to starch-lipid complexes. Starches added with oils and the control showed lower peak viscosity, trough viscosity final viscosity and setback but higher pasting temperature and delayed pasting time compared to native starch. Heat-moisture treatment with added vegetable oil showed promise as a process to prepare functional starch high in SDS and RS.

Quantitative metabolome analysis of boiled chicken egg yolk

Boiling has important effects on the texture of chicken eggs, but its effects on egg nutrients have not been systematically investigated. In this study, changes in the metabolites of egg yolks boiled under different heating intensities were quantified and compared by metabolomic analysis. A total of 797 metabolites were identified, and the abundance of 162 metabolites changed significantly after boiling. The significant reduction of L-lysine and D-fructose suggested that Maillard reactions occurred in over-boiled egg yolks. Egg yolk endogenous enzymes might induce a partial hydrolysis of proteins and phospholipids during the warm-up period of boiling, as the abundance of dipeptides, lysophospholipids, and free fatty acids was significantly increased in boiled egg yolks. Boiling increased the detectable abundance of fat-soluble vitamins, riboflavin, and biotin, possibly by altering the complex structure of protein-lipid-lipophilic compounds or denaturing vitamin-binding proteins. The results of metabolomic analyses provide important information for understanding the nutritional changes of egg yolk boiled under different heating intensities.

Effect of Heat–Moisture Treatment on the Physicochemical Properties, Structure, Morphology, and Starch Digestibility of Highland Barley (Hordeum vulgare L. var. nudum Hook. f) Flour

This study modified native highland barley (HB) flour by heat–moisture treatment (HMT) at different temperatures (90, 110, and 130 °C) and moisture contents (15%, 25%, and 35%). The effects of the treatment on the pasting, thermal, rheological, structural, and morphological properties of the native and HMT HB flour were evaluated. The results showed that HMT at 90 °C and 25% moisture content induced the highest pasting viscosity (3626–5147 cPa) and final viscosity (3734–5384 cPa). In all conditions HMT increased gelatinization temperature (T_o, 55.77–73.72 °C; T_p, 60.47–80.69 °C; T_c, 66.16–91.71 °C) but decreased gelatinization enthalpy (6.41–0.43 J/g) in the HMT HB flour compared with that in the native HB flour. The HB flour treated at 15% moisture content had a higher storage modulus and loss modulus than native HB flour, indicating that HMT (moisture content, 15%, 25%, and 35%) favored the strengthening of the HB flour gels. X-ray diffraction and Fourier-transform infrared spectroscopy results showed that HMT HB flour retained the characteristics of an A-type crystal structure with an increased orderly structure of starch, while the relative crystallinity could be increased from 28.52% to 41.32%. The aggregation of starch granules and the denaturation of proteins were observed after HMT, with additional breakage of the starch granule surface as the moisture content increased. HMT could increase the resistant starch content from 24.77% to 33.40%, but it also led to an increase in the rapidly digestible starch content to 85.30% with the increase in moisture content and heating temperature. These results might promote the application of HMT technology in modifying HB flour.

Monitoring the Changes in Heat Transfer and Water Evaporation of French Fries during Frying to Analyze Its Oil Uptake and Quality

The effect of frying temperature on heat transfer, water loss kinetic, oil uptake kinetic, and quality of French fries was evaluated. With increasing frying temperature, the core temperature of fries increased, and the Biot number and heat transfer coefficient (h) first decreased and then increased significantly (p < 0.05). The water loss rate (kw) and water effective diffusion of fries increased with the increasing frying temperature. The kw of fries fried at 150−190 °C were 0.2391, 0.2414, 0.3205, 0.3998, and 0.3931, respectively. The oil uptake rate (ko) first increased and then decreased with increasing frying temperature, and the ko of samples fried at 150−190 °C were 0.2691, 0.2564, 0.4764, 0.3387, and 0.2522, respectively. There were significant differences in the a*, L*, ΔE, and BI between fries with different temperatures (p < 0.05), while there was no significant difference in the b* (p > 0.05). The hardness and crispness of fries increased with increased frying temperature. The highest overall acceptability scores of fries were fried at 170 °C. Therefore, the changes in color, texture overall acceptability, and oil content were due to the Maillard reaction and the formation of porous structure, which was induced by h and water evaporation of fries when they changed.

Effect of Thermal Treatment on the Physicochemical, Ultrastructural, and Antioxidant Characteristics of Euryale ferox Seeds and Flour

Euryale ferox seeds (EFS) were less gelatinized, preventing the release of nutrients and functional compounds, resulting in limited applications in meals and the food industry. Nutraceutical importance of EFS includes starch, protein, lipids, 20 amino acids, minerals, and vitamins (C, E, and beta carotene). This study aimed to evaluate the effect of three different thermal treatments on EFS’s physicochemical and nutritional properties and expected to improve its applicability. The results showed that the bulk density, thousand-grain weight, and hardness of thermal treated EFS were significantly decreased (p < 0.05), whereas the maximum decrease was observed in the industrial infrared heating-assisted fluidized bed (IHFH) treatment. Meanwhile, there were more crevices, fissures, and heightened porous structures in EFS between the pericarp and episperm and the endosperm after heat treatment, which facilitated grinding and water absorption. Notably, EFS’s water and oil absorption capacities increased significantly (p < 0.05) with microwave and IHFH treatments. EFS ground’s solubility into powder was increased significantly with thermal treatment (p < 0.05). Furthermore, the functional properties of TPC, TFC, DPPH radical scavenging activity, and reducing power were significantly increased (p < 0.05). In general, the changes in the physicochemical properties of EFS and increased bioactivity were caused by microwave and IHFH treatments. Hence, it might improve the food value of EFS while providing valuable information to researchers and food manufacturers.