Heat-moisture Treatment Research Articles

Jicama (Pachyrhizus spp.), a nonconventional starch: Effects of citric acid and heat−moisture treatment on properties of starch and its application in film

AbstractBackground and ObjectivesThis study investigated the effects of citric acid (CA) and heat–moisture treatment (HMT) on the properties of jicama starch (JS). Furthermore, it explores the potential of modified jicama starch for film preparation.FindingsThe amylose content of the JS increases after HMT and decreases for CA‐modified starch. CA and HMT modification lowered the swelling power, solubility, peak viscosity, breakdown viscosity, final viscosity, setback viscosity, and crystallinity percentage compared to the native JS. After modification, there was an increase in the transition and pasting temperature of JS. The strong peak for the control and treated JS was observed at around 1008 cm−1 wavenumber in the Fourier transform infrared spectroscopy. SEM showed the overlapping and clusters of the granules in all the modified JS. Modified JS‐based film significantly affects the water solubility, barrier, and mechanical properties of film. The film's SEM showed that the CA‐ and HMT‐modified films had more homogeneous surfaces than the native JS film.ConclusionsHMT and CA modification significantly impacted JS properties and improved the film properties for further application.Significance and NoveltyThis study's findings will facilitate selecting an appropriate treatment to enhance the properties of JS for applications in food formulation and sustainable packaging.

Effects of moisture regulation and heat treatment synergy on structural properties and digestibility of jackfruit seed starch.

To investigate the impact of moisture regulation and heat treatment synergy on the structural properties and digestibility of jackfruit seed starch (JSS), starch samples underwent heat-moisture treatment (HMT) and annealing treatment (ANN) with varying moisture content (10-30 % for HMT at 120 °C, and 50-90 % for ANN at 40 °C). The physicochemical properties and in vitro digestibility of modified-JSS were systematically investigated. Results showed that the birefringence intensity of HMT-JSS decreased at high moisture levels but remained unchanged for HMT-JSS and ANN-JSS at low moisture levels. As moisture content increased for HMT and ANN, the amylose content and relative crystallinity increased and then slightly decreased. The gelatinization temperatures increased while enthalpy and viscosity declined. At high moisture content, the infrared absorbance ratio of 1047 cm-1/1022 cm-1 decreased on HMT but increased on ANN. Resistant starch (RS) content of both HMT-JSS and ANN-JSS was increased at appropriate moisture levels (10-15 % for HMT, 50-80 % for ANN), but decreased with excessive moisture. Besides, these changes were more pronounced on HMT than ANN. Correlation analysis showed that the RS was significantly affected by the short-range ordered structure during HMT and ANN. These results revealed that hydrothermal treatment efficiently modified the structure properties and digestibility of JSS.

Novel hydrothermal modification to alter functionality and reduce glycemic response of pea starch

Despite being an effective and clean-label method, heat-moisture treatment (HMT) is not commonly used for starch modification in industry due to the difficulty of scale-up. This study aimed to develop a novel method of using extrusion combined with high-temperature drying (EHTD) as an alternative to HMT for starch modification. Pea starch was subjected to extrusion at 37.5 % moisture level and with a low-temperature profile (≤ 65 °C), followed by immediate heating at 130 °C for 1 h. EHTD significantly damaged the granules, altered the X-ray diffraction pattern, and reduced the relative crystallinity of pea starch. Overall, EHTD-modified pea starch exhibited increased gelatinization temperatures and decreased gelatinization enthalpy change, lowered pasting viscosity and gel hardness, as well as enhanced enzymatic resistance than the native pea starch. More importantly, in a human feeding trial (n = 20 healthy participants) to monitor plasma glucose response over a period of 2 h after consuming water-boiled sample (35 g starch, dry basis), EHTD-modified pea starch exhibited 22 % reduction (p < 0.01) in plasma glucose incremental area under the curve as compared to the native counterpart. The results indicated that EHTD could be a new simple and clean-label method to produce functional and low-glycemic starch ingredients.

Enhancing resistant starch fraction in modified elephant foot yam starch: optimizing preparation conditions and exploring tribological properties

IntroductionElephant foot yam starch is highly susceptible to enzymatic digestion. To address this, heat-moisture treatment (HMT) has been used to modify its digestive properties and functionalities. However, when using modified starch in various food compositions, it is ultimately necessary to cook it in water-rich environments. The present work thus offers a systematic understanding of the heating and cooking procedures for modified starch, with a view to maintaining its structural and digestive properties.MethodsExperimental investigations employing X-ray diffraction, scanning electron microscopy, and enzymatic digestion have been utilized to gain insights into the characteristics of cooked starches. The interactions between amylose and amylopectin in native starch are more susceptible to disruption during cooking, which results in changes in texture and a reduction in resistant starch (RS) retention. Additionally, these preparations have been investigated by tribology to test structure and and friction.Results and discussionThe application of HMT has been observed to induce changes that stabilize the interactions between amylose and amylopectin, thereby ensuring better maintenance of granular integrity and higher RS retention under specific cooking conditions. The findings indicate that following a 2-min cooking period at 100°C, the modified elephant foot yam starch (EFYS) demonstrated enhanced granular stability, which was subsequently compromised after 10 min of cooking. Additionally, when modified elephant foot yam starch (EFYS) was heated at a temperature of 86°C for 2 and 6 min, it demonstrated superior preservation of resistant starch (RS) in comparison to a cooking time of 10 min. Moreover, the HMT starch exhibited the highest RS retention when cooked at 100°C for 2 and 6 min at approximately 39.12% and 20.23%, respectively. However, this retention decreased significantly to 1.08% after 10 min of cooking. Furthermore, the insights from tribology, when combined with the proposed naive models, enhance the understanding of how preparation conditions affect the functionalities of starches, which is crucial for designing food products with desired textural and nutritional qualities, especially in water-rich environments, where maintaining structural integrity and RS content is important.

Prolonging heat-moisture treatment time at medium moisture content optimizes the quality attributes of cooked brown rice through starch structural alteration

Brown rice (BR), one of the popular whole grains worldwide, is still limited to consumption due to its rough texture after cooking. Through inspecting structural alteration, this work discloses how heat-moisture treatment (HMT) moisture content (15 %–25 %) and time (1.0 h–3.0 h) modify the starch digestibility and cooked BR texture. The medium moisture content (20 %) allowed the highest pasting viscosity and a uniform network structure of cooked BR. Prolonging the HMT time from 1.0 h to 2.0 h at medium moisture content hindered starch swelling and improved stability. Meanwhile, the relative crystallinity, the surface compactness in nanoscale and R995/1022 decreased, while the gel network structure was improved, contributing to the softened cooked BR texture and the enhanced starch digestibility. Although the resistant starch content raised to 13.55 % after 3.0 h of HMT, the springiness, gumminess and chewiness of cooked BR degraded, and this should be considered in certain conditions.

Changes in structure, physicochemical properties and in vitro digestibility of quinoa starch during heat moisture treatment with hydrogen-infused and plasma-activated waters

In this study, comparative effect of heat moisture treatment (HMT) with distilled, hydrogen-infused and plasma-activated waters on the structure, physicochemical properties and in vitro digestibility of quinoa starch (QS) was investigated. To our knowledge, this study is the first to apply hydrogen-infused water to starch modification. The surface of HMT-modified samples was much rougher than that of native QS. HMT did not change the typical “A”-type X-ray diffraction pattern of QS but it increased its relative crystallinity. Meanwhile, amylose content, gelatinization temperature and water absorption capacity of QS significantly increased, whereas viscosity and swelling power markedly decreased. The rapidly digestible starch level of HMT-treated samples was significantly lower than that of native QS, and the resistant starch content markedly increased. These alterations were dependent on treatment moisture level. Furthermore, compared to distilled water, the HMT with hydrogen-infused and plasma-activated waters induced much more extensive effect on above properties, and the sample treated with plasma-activated water had the highest extent due to the acidic or alkaline environment and reactive oxygen and nitrogen species. These results identified that the combination of HMT with hydrogen-infused or plasma-activated water was a novel strategy to improve the thermal stability and functionality of quinoa starch.

The role of microwave absorption capacity and water mobility in the microwave treatment of grain vs. flour: Impact on the treated flour characteristics

Four alternative crops (amaranth, buckwheat, quinoa, and sorghum) were subjected to microwave-assisted heat-moisture treatment (MWT) under identical conditions (100 °C for 30 min at 25% moisture content) in two different forms (grain and flour). The effects of MWT on the microstructure, thermal properties, and techno-functional properties of the resulting flours were evaluated. The microwave absorption capacity and water mobility in flours and grains during heating were also determined to explain the different impacts of MWT depending on the matrix and its form. The results revealed that the microwave absorption capacity was comparable for all the samples, with water being the primary microwave-absorbing component. However, a different mobility and distribution of water during heating were observed for grains and flour and among matrices, leading to variations in the properties measured. The matrix, the form of treatment, and their interaction significantly influenced most of the analysed properties. MWT resulted in disruption of the native structure with partial fusion and loss of integrity of constituents, reduction in gelatinisation enthalpy, increase in the extent of amylopectin retrogradation, increase in water absorption capacity, and decrease in emulsifying capacity. The water absorption index and water solubility index showed increments or decrements depending on the matrix and the form of treatment. Moreover, the MWT of grain proved effective in limiting the colour change observed in the MWT of flour while enhancing the water absorption capacity. These findings highlight the importance of controlling not only the MWT conditions, but also the form of the matrix, as this influences the mobility of water and the final flour properties.

Physicochemical, enzymatic and fermentation modifications improve resistant starch levels and prebiotic properties of porang (Amorphophallus oncophyllus) flour

SummaryPorang tubers (Amorphophallus oncophyllus) are one of the Araceae family plants, which naturally contain resistant starch (RS). The RS is able to provide health impacts such as reducing the glycaemic index (GI), preventing the formation of gallstones and cardiovascular disease, and increasing mineral absorption. This research aims to improve the RS and prebiotic properties of porang flour through physical, chemical, enzymatic and microbiological modifications. Research methods include modification with physical treatment of autoclaving‐cooling one and two cycles (AC‐1S and AC‐2S), microwave‐cooling (MWC), heat moisture treatment (HMT), annealing (ANN), chemical treatment with acid hydrolysis (HA), enzymatic treatment with pullulanase debranching (DP) and microbiological treatment with combined heating and cooling fermentation (FAC). The results showed that physical, chemical, enzymatic and fermentation modification techniques increased the characteristics of RS and the prebiotic properties of porang flour. The best modification method for porang flour was obtained in the DP treatment with the morphological characteristics of sharp‐surfaced granules, total starch 39.81%, amylose content 3.73%, amylopectin content 36.08%, reducing sugar content 16.31%, power digestibility 43.81%, very rapidly digestible starch (VRDS) 8.59%, rapidly digestible starch (RDS) 11.08%, slowly digestible starch (SDS) 23.60%, RS 56.73%, resistance to gastric acid 98.60%, lactic acid bacteria (LAB) viability 11.87 log cfu/ml, prebiotic effect 3.07, prebiotic index 2.46 and prebiotic activity 1.77.

Recent Advances in Physical Processing Techniques to Enhance the Resistant Starch Content in Foods: A Review.

The physical modification of starch to produce resistant starch (RS) is a viable strategy for the glycemic index (GI) lowering of foods and functionality improvement in starchy food products. RS cannot be digested in the small intestine but can be fermented in the colon to produce short-chain fatty acids rather than being broken down by human digestive enzymes into glucose. This provides major health advantages, like better blood sugar regulation, weight control, and a lower chance of chronic illnesses. This article provides a concise review of the recent developments in physical starch modification techniques, including annealing, extrusion, high-pressure processing, radiation, and heat-moisture treatment. Specifically, the focus of this paper is on the alteration of the crystalline structure of starch caused by the heat-moisture treatment and annealing and its impact on the resistance of starch to enzymatic hydrolysis, as well as the granular structure and molecular arrangement of starch caused by extrusion and high-pressure processing, and the depolymerization and crosslinking that results from radiation. The impacts of these alterations on starch's textural qualities, stability, and shelf life are also examined. This review demonstrates how physically modified resistant starch can be used as a flexible food ingredient with both functional and health benefits. These methods are economically and ecologically sustainable since they successfully raise the RS content and improve its functional characteristics without the need for chemical reagents. The thorough analysis of these methods and how they affect the structural characteristics and health advantages of RS emphasizes the material's potential as an essential component in the creation of functional foods that satisfy contemporary dietary and health requirements.

Comparison of quality characteristics of reconstituted glutinous rice flour and sweet dumplings with various beans.

This study blended five types of beans-florid kidney bean, red adzuki bean, chickpea, black bean, and white kidney bean-with glutinous rice flour (GRF) to create a synergistic heat-moisture treatment (HMT). We investigated the effects of this combination on the digestibility of the glutinous rice mixture and the quality of sweet dumplings. The inclusion of beans, along with HMT, altered the granular morphology, adhesive qualities, thermal characteristics, crystallinity, and protein secondary structure of the blended powders compared to GRF. Notably, the starch granules in the glutinous rice flour with red adzuki bean (R-GRF) were more complete in morphology, compact in structure, and exhibited higher heat stabilization and crystallinity, with significant changes in protein secondary structure. These modifications resulted in a low expected glycemic index (eGI) value of 52.01. Additionally, the quality assessment of the fast-frozen sweet dumplings showed that those made with red adzuki bean mixed with glutinous rice flour (R-SD) had superior texture, reduced cracking, and less water loss compared to those made with GRF (G-SD), while maintaining similar color and odor to G-SD. The eGI value of 52.21 for R-SD also fell within the low eGI range, indicating its potential for developing low-eGI foods for patients with T2DM and other special populations.

Optimization of Heat-Moisture Treatment Conditions for High-Amylose Starch and Its Application in High-Resistant Starch Triticale Noodles.

Heat-moisture treatment (HMT) is a widely used method for modifying starch properties with the potential to reduce the digestibility of high-amylose starch (HAS). This study aimed to optimize the HMT conditions for HAS and apply the resulting HMT-HAS to triticale noodles to develop low-glycemic-index products. HMT significantly increased the resistant starch (RS) content and decreased the rapidly digestible starch (RDS) content of HAS. The treatment conditions-temperature, heating time, and moisture content-were found to significantly influence the starch composition. Optimal HMT conditions were determined using response surface methodology: a temperature of 108 °C, a heating time of 5.8 h, and a moisture content of 25.50%. Under these conditions, the RS content of HMT-HAS was 60.23%, nearly double that of the untreated sample. Increasing the level of HMT-HAS in triticale noodles led to significant decreases in short-range order, relative crystallinity, and viscosities, while the RS content increased from 12.08% to 34.41%. These findings suggest that incorporating HMT-HAS into triticale noodles effectively enhances starch digestive resistance, supporting the development of functional, low-glycemic-index triticale-based foods.

Molecular motion behaviors of starch affect starch-polyphenol inclusion complex and digestibility among different stilbenes polyphenol structures

Starch-polyphenol V-type inclusion complex has become a hot topic due to its anti-digestibility and nutritional function. This paper aimed to explore the molecular motion behavior of starch affects starch-polyphenol inclusion complex and digestibility among different stilbene polyphenol structures (resveratrol (RA), pterostilbene (PB) and polydatin (PD) via the high-pressure homogenization (HPH) and heat moisture treatment (HMT) processes), which represented the fully extended and limited molecular motion behavior of starch, respectively. These results revealed distinct trends in complex formation among different stilbenes polyphenol structures, highlighting RA as particularly conducive to increasing single helix and V-type crystalline structures with the highest resistant starch (RS) content of 28.11 % due to its smaller steric hindrance. Novelty, in HPH environments with extended molecular motion behavior, the steric hindrance and hydrophobicity/CH-π interactions of polyphenols influence complex formation in the order of RA > PB > PD. Conversely, in HMT systems with limited molecular motion behavior, the limited movement of molecules emphasized the importance of hydrogen bond interactions between polyphenols and starch. Thus, the glucoside in PD enhanced its interaction with starch compared to methoxy-modified PB, leading to increased formation of inclusion complex with RS content of 18.61 %. Overall, these findings deepen the understanding of starch-polyphenol interactions.

Lotus (Nelumbo nucifera G.) seed starch: Understanding the impact of physical modification sequence (ultrasonication and HMT) on properties and in vitro digestibility

Native lotus (Nelumbo nucifera G.) seed starch (LSS) was single- and dual-modified by heat-moisture treatment (HMT), ultrasonication (US), HMT followed by the US (HMT-US), and the US followed by HMT (US-HMT). The modified lotus seed starch (LSS) was evaluated for its physicochemical, pasting, thermal, and rheological properties and in vitro digestibility. All treatments decreased the swelling power (10.52–14.0 g/g), solubility (12.20–15.95 %), and amylose content (23.71–25.67 %) except for ultrasonication (17.67 g/g, 17.90 %, 29.09 %, respectively) when compared with native LSS (15.05 g/g, 16.12 %, 27.12 %, respectively). According to the rheological study, G′ (1665–4004 Pa) was greater than G″ (119–308 Pa) for all LSS gel samples demonstrating their elastic character. Moreover, gelatinization enthalpy (17.56–16.05 J/g) increased in all treatments compared to native LSS (15.38 J/g). Ultrasonication treatment improved the thermal stability of LSS. The digestibility results showed that dual modification using HMT and US significantly enhanced resistant starch (RS) and reduced slowly digestible starch (SDS) in LSS. Cracks were observed on the surface of the modified LSS granules. Peak viscosity decreased in all modified starches except for ultrasonication, suggesting their resistance to shear-thinning during cooking, making them ideal weaning food components. The results obtained after different modifications in this study could be a useful ready reference to select appropriate modification treatments to produce modified LSS with desired properties depending on their end-use.

Functionality modulation of starch from lotus rhizome using single and dual physical modification

The effects of ultrasonication (US) assisted by pre- and post-treatment of heat-moisture treatment (HMT) on physicochemical, rheological, pasting, digestive, and thermal properties of lotus rhizome (LR) starch were investigated in this study. All treatments decreased the swelling power, amylose content, and peak viscosity except for the ultrasonicated sample when compared with native LR starch. All treatments showed similar diffraction patterns with different intensities. FTIR spectra characteristic peaks did not emerge or disappear after single and dual modifications. Storage modulus (G′) is greater than loss modulus (G″) for all LR starch gel samples demonstrating their elastic character. Moreover, ΔHgel (253.1–303.7 J/g) increased in all treatments. Dual modification (HMT & US) significantly enhanced resistant starch and reduced SDS in LR starches. These results could be beneficial for promoting ultrasound processing for potential uses in the food industry and starch production.

Modulating rice digestibility: Mechanisms of ultrasound, oleic acid and moist-heat treatments influence structural, physicochemical and digestive properties

The research compared the combined effect of ultrasound (160 W, 2 min), oleic acid (15%, 11 h), and moist-heat treatment (HMT, 25% moisture content, 110 °C, 2 h) with their individual treatment on rice grains. The results showed that ultrasound treatment created pores and cracks in the rice grains, facilitating an easier penetration for oleic acid to develop amylose-oleic acid complex during HMT. Compared to native raw rice (NR), both single and combined treatments significantly altered the morphology, reduced swelling power and solubility, enhanced hydrophilicity, thus changing the moisture distribution, thermal and pasting characteristics. Notably, the combined treatment of three techniques significantly increased the relative crystallinity, accompanied by the highest digestive resistance, and the content of resistant starch was increased from 20.53% in NR to 31.75%, much higher than the other treatments. These findings provide potential for the manufacturers to rationally and flexibly employ this low digestible rice in health food products.

Removal of proteins and lipids affects structure, in vitro digestion and physicochemical properties of rice flour modified by heat-moisture treatment.

The objective of this experiment was to investigate the role of endogenous proteins and lipids in the structural and physicochemical properties of starch in heat-moisture treatment (HMT) rice flour and to reveal their effect on starch digestibility under heat. The findings indicate that, in the absence of endogenous proteins and lipids acting as a physical barrier, especially proteins, the interaction between rice flour and endogenous proteins and lipids diminished. This reduction led to fewer starch-protein inclusion complexes and starch-lipid complexes, altering the granule aggregation structure of rice flour. It resulted in a decrease in particle size, an increase in agglomeration between starch granules, and more surface cracking on rice granules. Under HMT conditions with a moisture content of 30%, slight gelatinization of the starch granules occurred, contributing to an increased starch hydrolysis rate. In addition, the elevated thermal energy effect of HMT enhanced interactions between starch molecular chains. These resulted in a decrease in crystallinity, short-range ordering, and the content of double-helix structure within starch granules. These structural transformations led to higher pasting temperatures, improved hot and cold paste stability, and a decrease in peak viscosity, breakdown, setback, and enthalpy of pasting of the starch granules. The combined analysis of microstructure, physicochemical properties, and in vitro digestion characteristics has enabled us to further enhance our understanding of the interaction mechanisms between endogenous proteins, lipids, and starches during HMT. © 2024 Society of Chemical Industry.

Gadung (Dioscorea hispida) tuber starch modified by freeze moisture treatment and heat moisture treatment: a study of functional, pasting, and physicochemical properties

ABSTRACT Gadung starch has limitations in several functional properties and thermal stability. Modifying starch through temperature treatments such as Freeze Moisture Treatment (FMT) and Heat Moisture Treatment (HMT) potentially improves these weaknesses. This research aimed to determine the effects of FMT and HMT on the functional, pasting, and physicochemical properties of gadung starch. This study consisted of a variety of treatments, namely native starch, FMT, HMT 100°C, HMT 110°C, FMT + HMT 100°C, and FMT + HMT 110°C. The results showed that FMT and HMT treatments significantly affected the functional, pasting, and physicochemical properties of gadung starch. The combination modification treatment of FMT + HMT 110°C increased swelling volume by 1.44 times, and water absorption capacity increased by 1.37 times. This was confirmed by the formation of porous and amorphous starch granules. Modified starch also had the best heat stability, as indicated by a low breakdown viscosity of 31.00 ± 9.90 cP. FMT+HMT110°C modified treatment was the best treatment because it had more pores, cracks, and higher swelling volume. The starch crystallinity index of modified starch decreased from 35.75 to 31.58 and changed the crystallinity type from B-type to A-type. The starch modification did not cause changes in functional groups but reduced crystallinity as indicated by the smaller ratio of the bands at 1045/1022 and the higher ratio at 1022/995 from FTIR spectra. Thus, FMT and HMT could effectively improve the characteristics of gadung starch by forming heat-stable amorphous starch.

Effect of chickpea thermal treatments on the starch digestibility of the fortified biscuits

Flour of roasted and heat-moisture treated chickpeas was used as a partial replacement of wheat flour, facilitating the development of biscuits with delayed digestion properties. The multiscale structural properties of starch and microstructural changes in chickpea flour and fortified biscuits were analyzed. Chickpea thermal treatment reduced the starch digestibility of fortified biscuits by 5.43%–7.33%, enhanced the resistant starch content of chickpea flour by 7.86%–12.28%. For thermal-treated chickpea fortified biscuits, the degree of relative crystallinity, short-range order, and double helix of starch was enhanced, the pasting viscosity was reduced, and the heat-moisture treatment showed a significant effect. Scanning electron microscope showed that fortified biscuits had a continuous and denser microstructure, reducing the accessibility of enzymes to hydrolyze starch molecules. The glycemic index values of fortified biscuits were reduced to below 66 in mice, as seen by their postprandial blood glucose response. Altogether, these results provide guidance for the development of delayed digestion meal replacement biscuits.

Effect of dry- and moist-heat treatment processes on the structure, solubility, and in vitro digestion of macadamia protein isolate.

This study aimed to enhance the solubility and digestibility of macadamia protein isolate (MPI) for potential utilization in the food industry. The impact of dry- and moist-heat treatments at various temperatures (80, 90, and 100°C) and durations (15 and 30min) on macadamia protein's microstructure, solubility, molecular weight, secondary and tertiary structure, thermal stability, and digestibility were investigated and evaluated. The heating degree was found to cause roughening of the MPI surface. The solubility of MPI after dry-heat treatment for 15 min at 100°C reached 290.96±2.80% relative to that of untreated protein. Following heat treatment, the bands of protein macromolecules disappeared, while MPI was stretched by vibrations of free and hydrogen-bonded hydroxyl groups. Additionally, an increase in thermal stability was observed. After heat treatment, hydrophobic groups inside the protein are exposed. Heat treatment significantly improved the in vitro digestibility of MPI, reaching twice that of untreated protein. The results also demonstrated that dry- and moist-heat treatments have distinct impacts on MPI, while heating temperature and duration affect the degree of modification. With a decreased ordered structure and increased random coil content, the dry-heat treatment significantly enhanced the in vitro digestibility of MPI. The digestibility of MPI after dry-heat treatment for 30 min at 90°C increased by 77.82±2.80% compared to untreated protein. Consequently, compared to moist-heat treatment, dry-heat treatment was more effective in modifying macadamia protein. Dry-heat treatment of 30 min at 90°C was determined as the optimal condition. PRACTICAL APPLICATION: Heat treatment enhances MPI characteristics, potentially advancing macadamia-derived food production, including plant-based beverages and protein supplements.

Effects of heat‐moisture treatment on the multiscale structure and digestibility of sweet potato starch

SummaryThe effects of water content on the multi‐scale structure and digestibility of sweet potato starch (SPS) during heat‐moisture treatment (HMT) were studied, and the relationship between water content, starch structure and starch digestibility was analysed. The results showed that the surface of SPS granules changed after HMT, mainly in the form of depression, rupture and adhesion, and the change was more obvious with the increase of water content, and the crystalline structure changed from the original A‐type to A + V‐type. The relative crystallinity and double helix content decreased, the thickness of semi‐crystalline layered structure increased, and the peak intensity decreased. The molecular weight of SPS after HMT tended to be distributed in the low molecular weight range of 4 × 104 g mol−1 &lt; Mw &lt;4 × 105 g mol−1. These structural changes promoted the rearrangement of the intermolecular structure of SPS, which made amylase shield the original action site when acting on SPS, and converted part of rapidly digestible starch (RDS) content into slow digestible starch (SDS) and resistant starch (RS) content, resulting in the increase of SDS and RS content. Especially in HMT‐25, the RS content of SPS was the highest, which was 28.60%. The experimental data can provide theoretical support for broadening the application of SPS.