Impact of pressure on physicochemical properties of starch dispersions

Rheological properties, multiscale structure, and in vitro digestibility of a maize starch-konjac glucomannan-bamboo leaf flavonoid complex modified by dynamic high-pressure microfluidization

The effects of dynamic high-pressure microfluidization (DHPM) treatment on the rheological properties, multiscale structure and in vitro digestibility of complex of maize starch (MS), konjac glucomannan (KGM), and bamboo leaf flavonoids (BLFs) were investigated. Compared with MS, the MS-KGM-BLF complex exhibited reduced viscosity and crystallinity, along with increased lamellar thickness to 10.26 nm. MS-KGM-BLF complex had lower viscosity after DHPM treatment. The highest ordered structure and crystallinity were observed at 50 MPa, with the α value increasing from 3.40 to 3.59 and the d value decreasing from 10.26 to 9.81 nm. However, higher DHPM pressures resulted in a decrease in the α value and an increase in the d value. The highest gelatinization enthalpy and resistant starch content were achieved at 100 MPa DHPM, while the fractal structure shifted from surface fractal to mass fractal at 150 MPa. This study presents an innovative method for enhancing the properties of MS.

Structural, physicochemical and functional properties of high-pressure modified white finger millet starch

The effect of high-pressure processing (HPP) modification (200, 400, and 600 MPa for 10 min) on the physico-chemical, functional, structural, and rheological properties of white finger millet starch (WFMS) was studied. Measured amylose content, water, and oil absorption capacity, alkaline water retention, and pasting temperature increased significantly with the intensity of pressure. All color parameters (L, a, b values, and ΔC) were affected by HPP treatment, and paste clarity of modified starch decreased significantly with an increase in storage time. The samples' least gelation concentration (LGC) is in the range of 8-14 %. An increasing solubility and swelling power are noted, further intensifying at the elevated temperature (90 °C). The structural changes of WFMS were characterized by XRD, SEM, and FTIR spectroscopy. Starch modified at 600 MPa showed a similar pattern as 'B'-type crystalline, and the surfaces of starch deformed because of the gelatinization. Applied pressure of 600 MPa affected the FTIR characteristic bands at 3330, 2358, and 997 cm-1, indicating a lower crystallinity of the HPP-600 modified sample. According to DSC analysis, even at 600 MPa, WFMS is only partially gelatinized. This work provides insights for producing modified WFM starches by a novel physical modification method.

Structure and properties of Quercus robur acorn starch extracted by pulsed electric field technology

Pulsed electric field (PEF) technology was used to extract starch from Q. robur flours using low-intensity electric fields (0 and 0.1 kV/cm) and study the impact of PEF on the structure and properties of acorn starch concerning commercial starch. PEF technology is an advantageous method for starch extraction than the aqueous steeping from an industrial perspective since reduces extraction time and allows for continuous processing of larger suspension volumes. PEF technology preserved the amylose and amylopectin contents, hydrogen bonds, and diffraction patterns, as well as the starch native properties. Hence, PEF could be used to obtain native starches, but future studies should verify its economic viability. Acorn starches have lower damaged starch content, gelatinization temperatures, enthalpies, improved pseudoplastic behavior, reduced in-vitro digestibility, and lower resistance to deformation compared to commercial corn starch. The higher solubility and swelling power of acorn starches up to 80 °C make them a suitable food additive in fermented yogurt and milk products and thus help to value acorn and acorn starches. Hence, acorns can be used to obtain native starches, a food ingredient with a wide range of food and non-food usage, using PEF.

Investigation of the in vitro biological activities of polyethylene glycol-based thermally stable polyurethane elastomers

The intense urge to replace conventional polymers with ecofriendly monomers is a step towards green products. The novelty of this study is the extraction of starch from the biowaste of wheat bran (WB) and banana peel (BP) for use as a monomer in the form of chain extenders. For the synthesis of polyurethane (PU) elastomers, polyethylene glycol (PEG) bearing an average molecular weight Mn = 1000 g mol-1 was used as a macrodiol, which was reacted with isophorone diisocyanate (IPDI) to develop NCO-terminated prepolymer chains. These prepolymer chains were terminated with chain extenders. Two series of linear PU elastomers were prepared by varying the concentration of chain extenders (0.5-2.5 mol%), inducing a variation of 40 to 70 wt% in the hard segment (HS). Fourier-transform infrared (FTIR) spectroscopy confirmed the formation of urethane linkages. Thermal gravimetric analysis (TGA) showed a thermal stability of up to 250 °C. Dynamic mechanical analysis (DMA) revealed a storage modulus (E') of up to 140 MPa. Furthermore, the hemolytic activities of up to 8.97 ± 0.1% were recorded. The inhibition of biofilm formation was investigated against E. coli and S. aureus (%), which was supported by phase contrast microscopy.

The Application of High-Hydrostatic-Pressure Processing to Improve the Quality of Baked Products: A Review

The current trend in the food industry is towards "clean label" products with high sensory and nutritional quality. However, the inclusion of nutrient-rich ingredients in recipes often leads to sensory deficiencies in baked goods. To meet these requirements, physically modified flours are receiving more and more attention from bakery product developers. There are various findings in the literature on high hydrostatic pressure (HHP) technology, which can be used to modify various matrices so that they can be used as ingredients in the baking industry. HHP treatments can change the functionality of starches and proteins due to cold gelatinization and protein unfolding. As a result, the resulting ingredients are more suitable for nutrient-rich bakery formulations. This review describes the information available in the literature on HHP treatment conditions for ingredients used in the production of bakery products and analyses the changes in the techno-functional properties of these matrices, in particular their ability to act as structuring agents. The impact of HHP-treated ingredients on the quality of dough and bakery products and the effects on some nutritional properties of the treated matrices have been also analysed. The findings presented in this paper could be of particular interest to the bakery industry as they could be very useful in promoting the industrial application of HHP technology.

Modification of Acorn Starch Structure and Properties by High Hydrostatic Pressure

Despite being rich in starch, over half of acorn production is undervalued. High hydrostatic pressure was used to modify the properties of Q. pyrenaica (0.1 and 460 MPa for 20 min) and Q. robur (0.1 and 333 MPa for 17.4 min) acorn starches to obtain high-valued ingredients. Pressure significantly altered the span distribution and heterogeneity of the acorn starch granules depending on the species, but their morphology was unaffected. Pressurization increased the amylose/amylopectin ratio and damaged starch contents, but the effect was more prominent in Q. pyrenaica than in Q. robur. However, the polymorphism, relative crystallinity, gelatinization temperatures, and enthalpies were preserved. The pressure effect on the starch properties depended on the property and species. The solubility, swelling power, and acorn gels' resistance towards deformation for both species decreased after pressurization. For Q. pyrenaica starch, the in vitro digestibility increased, but the pseudoplastic behavior decreased after pressurization. No differences were seen for Q. robur. Regarding the commercial starch, acorn starches had lower gelatinization temperatures and enthalpies, lower in vitro digestibility, lower resistance towards deformation, superior pseudoplastic behavior, and overall higher solubility and swelling power until 80 °C. This encourages the usage of acorn starches as a new food ingredient.

A Preliminary Study on the Release of Bioactive Compounds from Rice Starch Hydrogels Produced by High-Pressure Processing (HPP)

This work aimed to carry out a preliminary study on the release of bioactive compounds loaded into starch-based hydrogels produced by high-pressure processing (HPP). As a study case, the experiments were carried out on rice starch HPP hydrogels. Rice starch (20% w/w) and green tea extract (2% w/w), suspended in distilled water, were treated by HPP at processing conditions enabling starch gelatinisation, namely 600 MPa for 15 min at room temperature. Additional experiments were carried out on samples that were further loaded with glycerol (5% w/w). Gel formation was assessed by analysing the gelatinisation extent, structuring level, and swelling power of the samples. At the processing conditions utilised, stable hydrogels were obtained even in the presence of the extract and/or the glycerol in the starch suspension. As expected, the colour of the hydrogels formed was affected by the addition of green tea extract in the starch solution. HPP starch hydrogels were characterised by Fourier transform infrared spectroscopy (FT-IR) to determine the interactions between the different compounds utilised in the formulation. Moreover, the release kinetics of bioactive compounds from HPP rice starch hydrogels was evaluated using a vertical Franz diffusion cells system, simulating a transdermal pattern. The diffusion of bioactive compounds was measured spectrophotometrically and via HPLC analysis. A controlled release of bioactive compounds from the hydrogel structure was detected, suggesting that small molecules, such as polyphenols, positively interacted with the rice starch HPP hydrogel network that allowed a smooth and constant release of these bioactive compounds over time.

High hydrostatic pressure (HHP) reinforces solid encapsulation of d-limonene into V-type starch and its application in strawberry storage

The formation of inclusion complexes (ICs) between V-type starch and flavors is traditionally conducted in an aqueous system. In this study, limonene was solid encapsulated into V6-starch under ambient pressure (AP) and high hydrostatic pressure (HHP). The maximum loading capacity reached 639.0 mg/g after HHP treatment, and the highest encapsulation efficiency was 79.9 %. X-ray Diffraction (XRD) results showed that the ordered structure of V6-starch was ameliorated with limonene, which avoided the reduction of the space between adjacent helices within V6-starch generated by HHP treatment. Notably, HHP treatment may force molecular permeation of limonene from amorphous regions into inter-crystalline amorphous regions and crystalline regions as the Small-angle X-ray scattering (SAXS) patterns indicated, leading to better controlled-release behavior. Thermogravimetry analysis (TGA) revealed that the solid encapsulation of V-type starch improved the thermal stability of limonene. Further, the release kinetics study showed that a complex prepared with a mass ratio of 2:1 under HHP treatment sustainably released limonene over 96 h and exhibited a preferable antimicrobial effect, which could extend the shelf life of strawberries.

Effects of the Amylose/Amylopectin Content and Storage Conditions on Corn Starch Hydrogels Produced by High-Pressure Processing (HPP)

In this study, the effects of the amylose/amylopectin content on starch gelation and the physical characteristics of hydrogels produced by HPP were studied by optical and rheological measurements in steady-state conditions. Additionally, the effects of the storage temperature (4 °C and 20 °C) and type of packaging (plastic bags or sealed Petri dishes) on the physical stability of the hydrogels were evaluated for 30 days of storage by evaluating the shrinkage of the granules, as well as the weight loss, water activity, organoleptic, and rheological properties. The experimental findings suggested that amylose plays an antagonistic role in determining the capacity of the starch granules to absorb water under pressure and to create stable and structured gels and on the physical stability of hydrogels due to its influence over the starch retrogradation extent during storage. Twenty per cent amylose was the minimum concentration to form stable corn starch HPP hydrogels with good physical and rheological properties. Moreover, a storage temperature of 20 °C and the use of polymeric bags were evaluated as the most suitable storage conditions and packaging materials enabling the long storage of corn starch hydrogels.

Structural and Physicochemical Properties of Starch from Rejected Chestnut: Hydrothermal and High-Pressure Processing Dependence

The quality standards for the export of chestnuts generate large quantities of rejected fruits, which require novel processing technologies for their safe industrial utilization. This study aimed to investigate the impact of high-pressure processing (HPP) and hydrothermal treatments (HT) on the physicochemical properties of rejected chestnut starch. Chestnuts were treated by HPP at 400, 500, and 600 MPa for 5 min and HT at 50 °C for 45 min. In general, all HPP treatments did not induce starch gelatinization, and their granules preserved the integrity and Maltese-cross. Moreover, starch granules' size and resistant starch content increased with the intensity of pressure. Native and HT chestnut starches were the most susceptible to digestion. HPP treatments did not affect the C-type crystalline pattern of native starch, but the crystalline region was gradually modified to become amorphous. HPP-600 MPa treated starch showed modified pasting properties and exhibited the highest values of peak viscosity. This study demonstrates for the first time that after HPP-600 MPa treatment, a novel chestnut starch gel structure is obtained. Moreover, HPP treatments could increase the slow-digesting starch, which benefits the development of healthier products. HPP can be considered an interesting technology to obtain added-value starch from rejected chestnut fruits.

A study on the structural, physicochemical, rheological and thermal properties of high hydrostatic pressurized pearl millet starch

Starch in native form has limited application due to functional and physicochemical characteristics. To overcome these limitations, starch can be modified by non-thermal technologies such as high hydrostatic pressure (HHP). This study investigates high-pressure-induced gelatinization and the effect of this process on the structural, functional, morphological, pasting, thermal, physical and rheological properties of millet starch. The suspension of millet starch and water was pressurized at 200, 400 and 600 MPa for 10, 20 and 30 min to modify the starch in terms of structure, morphology, some physicochemical and rheological properties. Swelling strength and starch solubility decreased as a result of treatment with HHP. All treatments caused to increase in water holding capacity of the starch (from 0.66 % for native starch to 2.19 % for 600 MPa-30 min). Thermal analysis showed a decrease in gelatinization temperature and enthalpy of gelatinization and the pasting properties showed a decrease in the peak viscosity after HHP treatment. In addition, HHP treatment caused to increase in the hydration ability of starch by creating porosity and gaps in the granule surface and increasing the specific surface area. HHP application resulted in an increase in the peak time and pasting temperature and a decrease in breakdown and peak viscosities, final viscosity and setback viscosity in comparison with native starch of millet. The starch sample treated with 600 MPa for 30 min had the lowest syneresis and retrogradation ability. Increasing pressure and the time led to an increase in the elastic nature of the starch samples. According to the results, it is possible to increase usage area of starches in the food industry by improving its technological with HHP. This green physical technology can influence the quality parameters of starch, which can provide benefits for product machining and economic purposes.

Impacts of sonication and high hydrostatic pressure on the structural and physicochemical properties of quinoa protein isolate dispersions at acidic, neutral and alkaline pHs

Herein, 1 wt% quinoa protein isolate (QPI) was exposed to sonication using a 20 kHz ultrasonicator equipped with a 6 mm horn (14.4 W, 10 mL, up to 15 min) or high hydrostatic pressure (HHP, up to 600 MPa, 15 min) treatments at pH 5, pH 7, and pH 9. The changes to physicochemical properties were probed by SDS-PAGE, FTIR, free sulfhydryl group (SH), surface hydrophobicity (H₀), particle size and solubility. As revealed by SDS-PAGE, substantial amounts of 11S globulin participated in the formations of aggregates via SS bond under HHP, particularly at pH 7 and pH 9. However, protein profiles of QPI were not significantly affected by the sonication. Free SH groups and surface hydrophobicity were increased after the sonication treatment indicating protein unfolding and exposure of the embedded SH and/or hydrophobic groups. An opposite trend was observed in HHP treated samples, implying aggregation and reassociation of structures under HHP. HHP and sonication treatments induced a decrease in ordered secondary structures (random coil and β-turn) accompanied with an increase in disordered secondary structures (α-helix and β-sheet) as probed by FTIR. Finally, the sonication treatment induced a significant improvement in the solubility (up to ∼3 folds at pH 7 and ∼2.6 folds at pH 9) and a reduction in particle sizes (up to ∼3 folds at pH 7 and ∼4.4 folds at pH 9). However, HHP treatment (600 MPa) only slightly increased the solubility (∼1.6 folds at pH 7 and ∼1.2 folds at pH 9) and decreased the particle size (∼1.3 folds at pH 7 and ∼1.2 folds at pH 9). This study provides a direct comparison of the impacts of sonication and HHP treatment on QPI, which will enable to choose the appropriate processing methods to achieve tailored properties of QPI.

Thermal properties of different types of starch: A review

Starch is present in high amount in various cereals, fruits and roots & tubers which finds major application in industry. Commercially, starch is rarely consumed or processed in its native form, thus modification of starch is widely used method for increasing its application and process stability. Due to the high demand for starch in industrial applications, researchers were driven to hunt for new sources of starch, including modification of starch through green processing. Thermal properties are significant reference parameters for evaluating the quality of starch when it comes to cooking and processing. Modification of starches affects the thermal properties, which are widely studied using Differential scanning calorimeter or Thermogravimetric analysis. It could lead to a better understanding of starch's thermal properties including factors influencing and expand its commercial applications as a thickener, extender, fat replacer, etc. in more depth. Therefore, the review presents the classification of starches, factors influencing the thermal properties, measurement methods and thermal properties of starch in its native and modified form. Further, this review concludes that extensive research on the thermal properties of new sources of starch, as well as modified starch, is required to boost thermal stability and extend industrial applications.

Physical, Chemical and Biochemical Modification Approaches of Potato (Peel) Constituents for Bio-Based Food Packaging Concepts: A Review

Potatoes are grown in large quantities and are mainly used as food or animal feed. Potato processing generates a large amount of side streams, which are currently low value by-products of the potato processing industry. The utilization of the potato peel side stream and other potato residues is also becoming increasingly important from a sustainability point of view. Individual constituents of potato peel or complete potato tubers can for instance be used for application in other products such as bio-based food packaging. Prior using constituents for specific applications, their properties and characteristics need to be known and understood. This article extensively reviews the scientific literature about physical, chemical, and biochemical modification of potato constituents. Besides short explanations about the modification techniques, extensive summaries of the results from scientific articles are outlined focusing on the main constituents of potatoes, namely potato starch and potato protein. The effects of the different modification techniques are qualitatively interpreted in tables to obtain a condensed overview about the influence of different modification techniques on the potato constituents. Overall, this article provides an up-to-date and comprehensive overview of the possibilities and implications of modifying potato components for potential further valorization in, e.g., bio-based food packaging.

Main animal fat replacers for the manufacture of healthy processed meat products

The technological, sensory, and nutritional characteristics of meat products are directly related to their animal fat content. Adding animal fat to meat products significantly influences their sensory properties, such as color, taste, and aroma. In addition, the physicochemical properties of fat decisively contribute to the texture of meat products, playing a fundamental role in improving the properties of viscosity, creaminess, chewiness, cohesiveness, and hardness. However, meat products' high animal fat content makes them detrimental to a healthy diet. Therefore, reducing the fat content of meat products is an urgent need, but it is a challenge for researchers and the meat industry. The fat reduction in meat products without compromising the product's quality and with minor impacts on the production costs is not a simple task. Thus, strategies to reduce the fat content of meat products should be studied with caution. During the last decades, several fat replacers were tested, but among all of them, the use of flours and fibers, hydrocolloids, mushrooms, and some animal proteins (such as whey and collagen) presented promising results. Additionally, multiple strategies to gel oils of vegetable origin are also a current topic of study, and these have certain advantages such as their appearance (attempts to imitate animal fat), while also improving the nutritional profile of the lipid fraction of the products meat. However, each of these fat substitutes has both advantages and limitations in their use, which will be discussed in subsequent sections. Therefore, due to the growing interest in this issue, this review focuses on the main substitutes for animal fat used in the production of meat products, offering detailed and updated information on the latest discoveries and advances in this area.

Effect of High-Pressure Processing on the Packaging Properties of Biopolymer-Based Films: A Review

Suitable packaging material in combination with high-pressure processing (HPP) can retain nutritional and organoleptic qualities besides extending the product’s shelf life of food products. However, the selection of appropriate packaging materials suitable for HPP is tremendously important because harsh environments like high pressure and high temperature during the processing can result in deviation in the visual and functional properties of the packaging materials. Traditionally, fossil-based plastic packaging is preferred for the HPP of food products, but these materials are of serious concern to the environment. Therefore, bio-based packaging systems are proposed to be a promising alternative to fossil-based plastic packaging. Some studies have scrutinized the impact of HPP on the functional properties of biopolymer-based packaging materials. This review summarizes the HPP application on biopolymer-based film-forming solutions and pre-formed biopolymer-based films. The impact of HPP on the key packaging properties such as structural, mechanical, thermal, and barrier properties in addition to the migration of additives from the packaging material into food products were systemically analyzed. HPP can be applied either to the film-forming solution or preformed packages. Structural, mechanical, hydrophobic, barrier, and thermal characteristics of the films are enhanced when the film-forming solution is exposed to HPP overcoming the shortcomings of the native biopolymers-based film. Also, biopolymer-based packaging mostly PLA based when exposed to HPP at low temperature showed no significant deviation in packaging properties indicating the suitability of their applications. HPP may induce the migration of packaging additives and thus should be thoroughly studied. Overall, HPP can be one way to enhance the properties of biopolymer-based films and can also be used for packaging food materials intended for HPP.

Evaluation of the Physical Stability of Starch-Based Hydrogels Produced by High-Pressure Processing (HPP)

Starch-based hydrogels are natural polymeric structures with high potential interest for food, cosmeceutical, and pharmaceutical applications. In this study, the physical stability of starch-based hydrogels produced via high-pressure processing (HPP) was evaluated using conventional and accelerated methods. For this purpose, conventional stability measurements, namely swelling power, water activity, texture, and organoleptic properties, as well as microbiological analysis of rice, corn, wheat, and tapioca starch hydrogels, were determined at different time intervals during storage at 20 °C. Additionally, to assess the stability of these structures, accelerated tests based on temperature sweep tests and oscillatory rheological measurements, as well as temperature cycling tests, were performed. The experimental results demonstrated that the physical stability of starch-based HPP hydrogels was interdependently affected by the microorganisms’ action and starch retrogradation, leading to both organoleptic and texture modifications with marked reductions in swelling stability and firmness. It was concluded that tapioca starch hydrogels showed the lowest stability upon storage due to higher incidence of microbial spoilage. Accelerated tests allowed the good stability of HPP hydrogels to be predicted, evidencing good network strength and the ability to withstand temperature changes. Modifications of the rheological properties of corn, rice, and wheat hydrogels were only observed above 39 °C and at stress values 3 to 10 times higher than those necessary to modify commercial hydrogels. Moreover, structural changes to hydrogels after cycling tests were similar to those observed after 90 days of conventional storage. Data obtained in this work can be utilized to design specific storage conditions and product improvements. Moreover, the accelerated methods used in this study provided useful information, allowing the physical stability of starch-based hydrogels to be predicted.

Methods for characterizing the structure of starch in relation to its applications: a comprehensive review

Starch is a major part of the human diet and an important material for industrial utilization. The structure of starch granules is the subject of intensive research because it determines functionality, and hence suitability for specific applications. Starch granules are made up of a hierarchy of complex structural elements, from lamellae and amorphous regions to blocklets, growth rings and granules, which increase in scale from nanometers to microns. The complexity of these native structures changes with the processing of starch-rich ingredients into foods and other products. This review aims to provide a comprehensive review of analytical methods developed to characterize structure of starch granules, and their applications in analyzing the changes in starch structure as a result of processing, with particular consideration of the poorly understood short-range ordered structures in amorphous regions of granules.

Effect of high-pressure pre-soaking on texture and retrogradation properties of parboiled rice

BACKGROUND

The poor palatability, low digestibility, and unpleasant color of parboiled rice (PR) have severely hampered its acceptance by consumers. It is hence necessary and urgent to develop a new method for producing high-quality PR. In the current study, the effect of high hydrostatic pressure (HHP) pre-soaking on the color, textural properties, and the degree of retrogradation of PR was investigated.

RESULTS

With HHP from 100 to 500 MPa, the water adsorption rate increased and cooking time decreased. Parboiled rice samples presented higher lightness scores (L) and had lower color intensity (B). Compared with a control group, PR samples treated with high-pressure pre-soaking showed a reduction of hardness values from 0.69% to 32.99%, and gumminess values also decreased from 8.58% to 33.62%. The differential scanning calorimetry (DSC) results indicated that the enthalpy values of PR samples decreased after high pressure pre-soaking. The molecular structure of PR characterized by Fourier transform infrared spectrometry confirmed that HHP pre-soaking could decrease the retrogradation level.

CONCLUSION

The findings outlined above suggest that the texture and retrogradation properties of PR were improved after high-pressure pre-soaking. © 2021 Society of Chemical Industry.

Evaluating high pressure-treated corn and waxy corn starches as novel fat replacers in model low-fat O/W emulsions: A physical and rheological study

High hydrostatic pressure-treated corn starch (HPCS) and waxy corn starch (HPWCS) at three concentrations (10%, 15%, and 20%) were applied as novel fat replacers in a model low O/W emulsion at three fat reduction levels (FR, 25%, 50%, and 75%) and some physical, textural and rheological characteristics and stability of the samples were examined and compared with the control. Applying higher concentrations of HPCS and HPWCS increased the zeta potential, hardness and consistency (mainly for HPWCS samples), reversely decreased the Z-average particle size and polydispersity index of the reduced-fat emulsions, but augmenting FR levels caused a reverse inclination. The rheological assay cleared that the emulsions prepared with HPWCS had greater elastic modulus (G') and more gap between G' and viscous modulus (G″) at all concentrations than the HPCS-contained samples. The critical stress (τ_c) of 25FR samples were significantly higher than the control, showing the well stability of reduced-fat samples. Also, the τ_c of the HPCS-contained emulsions reduced meaningfully when the FR level increased from 25% to 75%, but for the HPWCS samples, fat reduction didn't change the τ_c value significantly up to 50% fat reduction. Based on Tangδ_s(n-LVE), HPWCS contained samples showed more spreadability than the HPCS-contained emulsions.

New insights into starch gelatinization by high pressure: Comparison with heat-gelatinization

The effects of pressure and temperature on the gelatinization properties of wheat starch were investigated. The long-range crystallinity and short-range molecular order were gradually destroyed under both conditions as the degree of gelatinization (DG) increased. With increasing DG, differential scanning calorimetry (DSC) onset (T_o), peak (T_p) and conclusion temperatures (T_c) increased for the heat-gelatinized samples but did not change greatly for the pressure-gelatinized samples. At similar DG, pressure-gelatinization resulted in less granule swelling than heat-gelatinization. Lower degree of both heat- and pressure-gelatinization resulted in increased pasting viscosities and gel texture parameters, whereas the opposite was noted at higher DG. We conclude that pressure and heat induced starch gelatinization in different ways, resulting in different gel texture properties. Pressure-gelatinization disrupted both less stable and more stable crystallites, whereas less stable crystallites were preferentially disrupted during heat-gelatinization.

Characteristics of pasting properties and morphology changes of rice starch and flour under different heating modes

The pasting behavior of rice starch and its relationship with cooking properties of rice have been extensively studied. However, the viscosity changes of rice starch and flour under conventional cooking mode and high temperature and high pressure (HTHP) mode remain unknown. In this study, three typical rice starches and seven rice flours of different types and varieties were used to evaluate the effect of cooking modes on their pasting behaviors. A detailed discussion about the relationships among chemical composition, thermal properties, and crystallinity were conducted to explain the different pasting behaviors of the rice samples. The pasting behavior of rice starch was found to be similar with rice flour under standard and conventional heating modes, while remarkably different when treated at different HTHP levels, especially for sticky rice flour. The morphological changes of rice samples at 95 °C and 120 °C confirmed that high temperature long time heating caused extending of molecules, which exhibited layered structure at 120 °C. The rice flour samples showed different morphologies after heating at different modes due to varied amylose content and crystallinity, which contributed to different pasting behavior. These results provide useful information for developing strategies to control rice cooking and improve eating quality.