Gelatinization Research Articles

Starch multiscale structure and physicochemical property alterations in high-quality indica rice quality and cooked rice texture under different nitrogen panicle fertilizer applications

The starch multiscale structure, physiochemical properties, grain quality and cooked rice texture of high-quality early and late indica were analyzed under nitrogen panicle fertilizer (low panicle fertilizer, LPF; middle panicle fertilizer, MPF; high panicle fertilizer, HPF) treatments and their internal relations were investigated. Compared to the MPF treatment, the starch granules in HPF and LPF had more surface-proteins and irregular voids for high-quality early and late indica rice cultivars, respectively. Nitrogen panicle fertilization application increased amylopectin medium and long chains as well as protein content, resulting in higher relative crystallinity and gelatinization temperatures. Moderate changes in starch multistructures and physicochemical properties such as branching degree, amylopectin medium chain, and pasting viscosities derived from MPF treatment significantly improved processing, appearance qualities and cooked rice texture. Additionally, the decrease in starch branching, gelatinization temperatures, and granule uniformity along with an increase in large granules, breakdown, and △Hgel under MPF treatment were the main reasons for improving rice textural properties.

Use of annatto dye extraction residue as additive in the cassava starch composite foam tray

AbstractPigment extraction from annatto seed results in large amounts of by‐products (~97%) and residual carotenoid content. In this work, composite foam trays containing 90:10 (10AR), 80:20 (20AR), and 70:30 (30AR) cassava starch: annatto residue (AR) ratios were prepared by thermopressing. The physical–chemical properties, thermal stability, antioxidant activity, and biodegradability of the composite foam trays and cassava starch foam tray (control) were measured and compared. High AR ratio (20AR and 30AR) yielded thicker (2.1–2.3 mm), denser (0.72–0.74 g/cm3), and less porous (32.5–33%) composite foam trays than the control due to incomplete cassava starch gelatinization and the presence of fibers, lipids, and proteins in AR. Thus, the composite foam trays had lower mechanical resistance (0.4–0.8 MPa) and elongation (0.4%–0.7%) than the control (2.9 MPa and 1.5%). However, addition of high AR ratio increased the foam tray resistance to water and yielded colorful foam trays with antioxidant property as measured by DPPH• (0.11 to 0.52 μM TE/100 g) and ABTS•+ (7.86–53.77 μM TE/100 g). Increasing the AR ratio in the composite foam tray delayed the biodegradation time by 17 days as compared to the control, but all the foam trays were more biodegradable than EPS. Therefore, AR has potential use in the production of bioactive composite foam trays.

High gravity enzymatic hydrolysis of non–gelatinized starch from black - purple rice

Thanks to novel recombinant starch degrading enzymes which can directly hydrolyze raw starch at ambient temperature, the technology of hydrolysis of uncooked starch has recently been developed andproven to be effective. In combination with high substrate concentration (high gravity) approach, this technology not only saves the thermal energy for starch gelatinization but also reduces the impact of heat on valuable components in starch–containing raw materials. Black–purple rice is a specialty of Northwest Viet Nam, which contains high level of anthocyanin, a biologically active ingredient. In this study, commercial enzymes were applied to hydrolyze non–gelatinized black–purple rice to obtain anthocyanin–containing sugar solution. Factors affecting the starch conversion such as enzyme/substrate ratio, hydrolysis duration, temperature, and the presence of supporting enzymes in the hydrolysis process were investigated. The results showed that in the presence of Stargen 002, Viscozyme L, and Cellulast 1.5 L, more than 86 % of starch in a total of 320 g/L black-purple rice were converted into glucose after 72 hours at 50 °C. From black-purple rice, two products were received, including a glucose–rich hydrolysate (245.92 g/L) containing anthocyanin (30 mg/L) and a solid by–product rich in protein, which were very potential for food application.

The Effect of Different Milling Methods on the Physicochemical and In Vitro Digestibility of Rice Flour.

Preparation methods have been found to affect the physical and chemical properties of rice. This study prepared Guichao rice flour with wet, dry, semi-dry, and jet milling techniques. Differences in the particle size distribution of rice flour were investigated in order to assess their impact on pasting, thermal, gel, starch digestibility, and crystalline structure using an X-ray diffractometer (XRD) and a Rapid Visco Analyzer (RVA) across in vitro digestibility experiments. The results showed that semi-dry-milled rice flour (SRF) and wet-milled rice flour (WRF) were similar in damaged starch content, crystalline structure, and gelatinization temperature. However, compared with dry-milled rice flour (DRF) and jet-milled rice flour (JRF), SRF had less damaged starch, a higher absorption enthalpy value, and a higher gelatinization temperature. For starch digestibility, the extended glycemic index (eGI) values of WRF (85.30) and SRF (89.97) were significantly lower than those of DRF (94.47) and JRF (99.27). In general, the physicochemical properties and starch digestibility of WRF and SRF were better than those of DRF and JRF. SRF retained the advantages of WRF while avoiding the high energy consumption, high water consumption, and microbial contamination disadvantages of WRF and was able to produce better rice flour-associated products.

Effects of garlic peptides on rheology, moisture, microstructure, gluten distribution, and baking properties of dough

The effects of different proportions of Garlic Peptides (GPs) on wheat dough were investigated to improve the dough quality. The pasting, rheological properties, water migration and distribution, microstructure, protein polymerization, and baking behaviors of GPs on the dough were determined. Pasting results showed that GPs inhibited starch swelling and gelatinization, improved the gas production capacity of yeast, and promoted dough fermentation. Rheological properties showed that GPs had a moderate weakening effect on dough, thus reducing the viscoelasticity of dough. Meanwhile, GPs could effectively bind water molecules and inhibit the water migration. Moreover, GPs could change the gluten distribution in the dough, facilitating the development of gluten networks. In addition, baking characteristics showed that GPs helped produce bread with uniform internal structure and soft texture. Therefore, this study emphasized the potential role of GPs and showed the theoretical basis of interactions in peptides-dough systems.

Characterization of the alkali-induced protein cross-linking in buckwheat sourdough steamed bread

This study elucidated the alkali-induced protein cross-linking behaviors of buckwheat sourdough steamed bread (BSSB). When the alkali concentration increased to 1.5% (on a total flour weight basis), the protein extractability in sodium dodecyl sulfate (SDS) decreased by 2.29% while the disulfide (SS) bond content increased by 5.97 μmol/g protein, indicating that the alkali promoted the SS cross-linking of the proteins. The formation of dehydroalanine (DHA) and lanthionine (LAN) at alkali concentrations of 2.0% and 2.5% demonstrated the occurrence of DHA-derived cross-linking. To explore the role of SS cross-linking in the quality of BSSB, the thiol-blocking agent N-ethylmaleimide (NEM) was also employed. It was determined that the BSSB with NEM had almost no gas cells and that the specific volume was 48.41% lower than the control. The alkali increased the specific volume by up to 26.75% at 2.0% concentration and ameliorated the crumb structure of the BSSB. Dynamic thermo-mechanical analysis revealed that the alkali also delayed the starch gelatinization and gas cell opening, which may have contributed to the gas holding capacity of the BSSB. The amino acid residues involved in the DHA-derived cross-linking and the potential cross-linking sites were identified via liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis. It was found that both the Cys197 from wheat peroxidase and the Cys105 from the wheat alpha-amylase/trypsin inhibitor CM16 were crucial to the formation of the DHA-derived cross-links and that the LAN between two cysteines was inter-chain.

Use of red onion skin (Allium cepa L.) in the production of bioactive extract and application in water-absorbing cryogels based on corn starch

Onion skin is biomass commonly discarded in the environment, rich in bioactive compounds with antioxidant and antimicrobial potential; thus, we propose valorizing this residue using cryogels as carriers. This study aimed to produce bioactive cryogels based on corn starch and red onion skin extract (ROSE). Cryogels were prepared by starch gelatinization, with five freeze/thaw cycles, adding 5, 10, and 15% (w/w) of ROSE. The ROSE presented total phenols, flavonoids, and volatile organic compounds (VOCs), with esters being the majority. These compounds are responsible for the biological activity of ROSE. The cryogels displayed homogeneous morphology and randomly oriented pores. The water absorption capacity of the cryogels reached 658.3%. The cryogels showed low density reaching 0.153 g/cm3; high porosity of up to 83.76%; thickness of up to 0.83 cm; and low moisture of up to 3.4%. The texture profile showed that the incorporation of ROSE increased hardness. The ROSE incorporated in the cryogel had higher thermal stability when compared to its free form, increasing degradation temperature of about 155.28 °C. The cryogels with ROSE presented high antioxidant activity against ABTS and DPPH radicals ranging from 45.4 to 90.5%. In addition, they showed antibacterial action, with total inhibition of the proliferation of pathogenic bacteria Salmonella Typhimurium and Listeria monocytogenes. The cryogel, without ROSE presented greater in vitro degradability due to the breaking of the glycosidic bonds. The cryogels are efficient matrices with the potential for application as water absorbents in fresh food products that release exudates and carriers of antioxidant and antimicrobial compounds.

Comparison of the fine structure and physicochemical properties of proso millet (Panicum miliaceum L.) starch from different ecological regions

Field experiments were conducted to evaluate the morphology, granule size, fine structure, thermal properties, and pasting properties of starch from a waxy (139) and a non-waxy (297) varieties of proso millet grown in Yulin (YY) and Yangling (YL). Compared with the starches from the two varieties grown in YY, the starches from the two varieties grown in YL exhibited higher relative crystallinities, 1045/1022 cm−1 ratio, and amounts of amylopectin long branch chains (APL) but lower 1022/995 cm −1 ratio, amounts of amylopectin short branch chains (APs), and APs/APL ratios. Starches from YL also synthesized long branch-chain amylopectin to enhance intermolecular interactions and form a stable granular structure, which resulted in increased starch gelatinization temperature, enhanced shear resistance, and reduced setback viscosity. Starch from the waxy (139) variety has good application prospects in the food industry because of its high gelatinization temperature and light transmittance and low setback value, which can be ascribed to its extremely low amylose content, polydispersity index, high molecular weight, and dispersed molecular density. It may serve as a reference for applying proso millet starches in the food industry and developing breeding programs to improve starch quality.

Effect of Coating on Physico-Chemical Characteristics of Puffed Wheat Grains

Abstract Durum wheat (Triticum turgidum) is used for the production of various ready-to-eat products such as breakfast cereals, puffed grains, and extruded products. Technological processes of grain processing and the addition of different ingredients cause changes in the physical and chemical properties of the product, which give puffed grains a unique porous structure and change their nutritional value. This study aimed to evaluate the effect of coating on the physico-chemical characteristics of puffed wheat grains depending on the coating material. The study revealed that the application of coating increased dry matter and thousand-kernel weight (TKW). Water activity decreased in puffed grain without coating (BZ), and puffed grain with whey powder (MC) compared to wheat grain. The reduction in the moisture content increased the crispiness of product. Application of coating led to a decrease in the hardness of both MC and puffed wheat grain with vanillin and sugar (BV). Applying additives to the product’s surface led to a decrease in the water absorption index (WAI). The water solubility index (WSI) increased in the MC and BV samples. Samples BZ, BV and MC had higher L* (lightness) values than wheat grains because the puffing process expanded the cells, confirmed by scanning electron microscopy, and caused starch gelatinisation. The a* (redness) value of wheat was greater than that of BZ, BV and MC, which may be due to the partial removal of the outer layer of wheat grains. The milled samples of BZ, BV and MC were slightly darker, having lower L* values, compared to unprocessed wheat grain.

Effects of Salecan on the gelatinization and retrogradation behaviors of wheat starch

The retrogradation behavior of native wheat starch (WS) is undesirable for starchy food. Adding polysaccharides is a secure and effective method to improve starch properties. Herein, the effects of Salecan, a novel microbial polysaccharide, on WS's gelatinization and retrogradation behaviors were investigated. Results showed that Salecan increased peak, trough, and final viscosities while decreasing WS paste's breakdown and setback values, suggesting Salecan inhibited the short-term retrogradation of WS. The rheological results showed Salecan increased the viscosities of the gelatinized samples, and its storage moduli decreased initially and then increased when Salecan was added more than 10 g/kg. Moreover, Salecan significantly reduced the WS gel hardness during long-term storage. SEM and XRD results showed Salecan improved the microstructure and reduced the crystallinities of retrogradation WS gels, respectively. Furthermore, the application of Salecan in Chinese steamed bread showed Salecan could inhibit moisture migration and maintain the texture of prepared bread during chilled storage, demonstrated by LF-NMR and TPA, respectively. In summary, Salecan could inhibit the retrogradation of WS, and the recommended optimal added level is 10 g/kg of WS weight, which would be helpful for the development of starchy food with a longer shelf-life.

Changes in the physicochemical properties of isolated starch and plantain (Musa AAB Simmonds) flours for early maturity stage

This work focuses on the study of the physicochemical changes that take place during the first stage of ripening of plantain, with particular attention to the changes in the orthorhombic and hexagonal nanocrystals present in this starch, and its relation shift with resistance starch. Significant changes were observed in the proximal analysis of plantain flour. A gradual increase in moisture content was attributed to the high content of crystalline structures and molecules that can be removed by drying. Water activity increased with ripening, which was attributed to the hygroscopic nature of the flours. The protein content increased, and the carbohydrate content decreased, indicating the progress of biochemical reactions. The changes in the fat content are consistent with the hydrolysis and resynthesis of lipids during the ripening process. The obtained results indicate a significant influence of the ripening stage on the physicochemical properties of flour and starch of plantain, which is associated with the occurrence of a climacteric peak on the 4th day of ripening.The hydration properties of plantain flour decreased significantly during the ripening days, consistent with the occurrence of a climacteric peak. Water holding capacity (WHC) and water binding capacity (WBC) were affected by the degree of digestion of native starch granules and protein denaturation during fruit ripening. Scanning electron microscopes (SEM) showed that during ripening the surface of the isolated starches do not suffer any significative damage. X-ray diffraction patterns were used to identify crystalline structures and to study the changes in the crystalline structures. These results showed that the starch contains orthorhombic and hexagonal nanocrystals, which play and important role and which show small structural damage during ripening reflected in a decrease in their relative crystallinity. This is the first time that these nanocrystals have been studied and considered in the ripening process. Differential scanning calorimetry was used to study the thermal transition in isolated starch. The results indicated that the gelatinization of starch corresponds to the solvation of orthorhombic and hexagonal nanocrystals, and that during ripening there is a decrease in the enthalpy reflecting some crystal structural damage. Pasting properties were studied using a Starch cell for flours and isolated starches, indicating that the pasting profile is governed by intrinsic and extrinsic factors. The resistant starch does not show significant changes at this stage of maturation. This starch is the one with the highest resistant starch content reported in the literature (38%). It was hypothesized that the resistant starch is directly related to the amount of whole starch granules, and more importantly, directly related to the number concentration of orthorhombic and hexagonal nanocrystals. Therefore, knowledge of the physicochemical and nutritional properties of plantain and flour at each stage of ripening allows better selection according to industrial applications.

Effect of Ball-Milling on Starch Crystalline Structure, Gelatinization Temperature, and Rheological Properties: Towards Enhanced Utilization in Thermosensitive Systems.

Starch's crystalline structure and gelatinization temperature might facilitate or hinder its use. Ball milling has frequently been mentioned in the literature as a method for reducing starch size and as a more environmentally friendly way to change starch, such as by increasing surface area and reactivity, which has an impact on other starch properties. In this study, starch samples were milled for varying durations (1, 5, 10, 20, and 30 h) and at different starch-to-ball mass ratios (1:6 and 1:20). Microscopy and XRD revealed that prolonged milling resulted in effective fragmentation and a decrease in crystallinity of the starch granules. Increasing milling times resulted in an increase in amylose content. Rheology and thermal studies revealed that gelatinization temperatures dropped with milling duration and that viscosity and thixotropy were directly influenced. The samples milled for 10, 20, and 30 h at a ratio of 1:20 were the most fragmented and upon drying formed a transparent film at ambient temperature, because of the lower gelatinization temperature. Starch ball milling could lead to the use of this material in thermosensitive systems.

Designing a Specific Pretreatment on Corn Starch to Facilitate Enzymatic Rearrangement of Glycosidic Bonds for Efficiently Reducing Starch Digestibility.

Bacterial 1,4-α-glucan branching enzymes (GBEs) provide a viable strategy for glycosidic bond rearrangement in starch and regulation of its digestion rate. However, the exponential increase in paste viscosity during starch gelatinization has a detrimental effect on the catalytic action of GBEs, thereby limiting productivity and product performance. Here, we designed an enzymatic treatment on corn starch granules by the GBE from Rhodothermus obamensis STB05 (Ro-GBE) prior to the glycosidic bond rearrangement of gelatinized starch catalyzed using the GBE from Geobacillus thermoglucosidans STB02 (Gt-GBE). Specifically, a moderate amount of Ro-GBE was required for the pretreatment stage. The dual GBE modification process enabled the treatment of more concentrated starch slurry (up to 20%, w/w) and effectively reduced starch digestibility. The resulting product contained a rapidly digestible starch fraction of 66.0%, which was 11.4% lower than that observed in the single Gt-GBE-modified product. The mechanistic investigation showed that the Ro-GBE treatment promoted swelling and gelatinization of starch granules, reduced starch paste viscosity, and increased the mobility of water molecules in the starch paste. It also created a preferable substrate for Gt-GBE. These changes improved the transglycosylation efficiency of Gt-GBE. These findings provide useful guidance for designing an efficient process to regulate starch digestibility.

Rapid and nondestructive identification of adulterate capsules by NIR spectroscopy combined with chemometrics

This study aims to develop a rapid and non-destructive method to identify counterfeit and substandard drugs, addressing the critical need for better quality control in drug production. According to the reasons for counterfeit products in actual production, the commonly used solid preparation excipients such as HPMC, MCC, Mg-St and Pregelatinized Starch, as well as three chemical drugs with similar efficacy to Guizhi-Fuling (GZFL) Capsule as adulterants, including Aspirin, Ibuprofen and Sinomenine Hydrochloride were selected and designed as adulteration samples with different levels of adulteration. NIR spectra were collected in a non-invasive mode and analyzed by one-class classification methods. The feasibility of using Near-infrared (NIR) spectroscopy as a detection method to qualitatively identify adulterated samples was explored at three packaging levels of powder, intact capsules and capsules in PVC. The differences between the samples were analyzed by NIR spectra comparison, cluster analysis and principal component analysis. The performance of SVM, OCPLS and DD-SIMCA models in dealing with the authentication of genuine and counterfeit products was established and compared. The results show that the spectra contain sample information and the adulterated samples could be discriminated correctly by established models. Moreover, applying appropriate spectral preprocessing methods can further improve the model's performance. In addition, a PLS regression model was developed to predict the adulteration levels of the three packing level samples, which yielded satisfactory results. This study highlights the potential of NIR spectroscopy combined with Chemometrics as a rapid and non-destructive testing analysis method to accurately identify counterfeit and substandard drugs, thereby ensuring drug quality.

Hydrocolloids-aided control of oil penetration and distribution in deep-fried breaded fish nuggets

To investigate the effect of hydrocolloids on oil penetration and distribution in fried batter-breaded fish nuggets (BBFNs), sodium carboxymethyl cellulose (CMC-Na), guar gum (GG), and xanthan gum (XG) were individually blended (0.2 or 0.3%, w/w) into the mixture (1:1, w/w) of wheat gluten (WG) and wheat starch (WS) to form batters. The moisture absorption capacity of XG was found to be the highest, followed by CMC-Na, GG, WG, and WS. Hydrocolloids increased the batter viscosity, shear modulus, WS gelatinization and WG denaturation temperatures, BBFNs pick-up, thermogravimetry temperature, and the bound water content in crust. This trend was opposite with enthalpy change (ΔH) during starch gelatinization and protein denaturation, both of which lessened pores and cracks, leading to an inhibition of oil penetration into fried BBFNs. Of the three hydrocolloids, XG exhibited the greatest effect, followed by CMC-Na and GG. Therefore, XG was suitable for reducing fat content of fried BBFNs. Overall, the hydrophilic and thickening capabilities of the three studied hydrocolloids and their interactions with WS and WG altered the batter characteristics and reinforced the thermal stability of the crust, thereby reducing oil penetration and distribution in deep-fried BBFNs. This work will not only provide new ideas to clarify oil penetration based on hydrocolloids for fried BBFNs, but also provide scientific instructions for the large-scale production of low-fat fried batter-breaded foods.

Pengaruh Jenis Warna Umbi Ubi Jalar (Ipomea Batatas L.) Dan Lama Pengukusan Terhadap Karakteristik Kimia Dan Fisik Mie Kering

Dry noodles are dried food products made from wheat flour with the addition of other foods and food additives which are allowed to be in the form of typical noodles. The high increase in consumption and demand for noodles will simultaneously increase the volume of wheat imports. Excessive consumption of wheat flour will have an allergic effect for celiac sufferers. Sweet potato pasta as a local food can be used to reduce on imported flour and provide health effects as an antioxidant for people with diabetes mellitus. The difference in sweet potato color can affect the physicochemical and functional characteristics of sweet potatoes. In the steaming process, starch gelatinization and gluten coagulation occur so that the occurrence of dehydration of water from gluten will cause noodle elasticity. Steaming needs to be considered to form a cohesive and fairly elastic dough period.

Hydrogel properties of non-conventional starches from guabiju, pinhão, and uvaia seeds

The physicochemical properties of starch vary depending on the botanical sources, thereby influencing the gelatinisation/retrogradation properties and subsequently affecting the hydrogels characteristics. This study aimed to assess the influence of botanical sources influence on starch and hydrogel properties using non-conventional starch derived from guabiju, pinhão, and uvaia seeds. Hydrogels were prepared by starch gelatinisation followed by 6 h ageing period at room temperature (20 ± 2 °C) and subjected to five freeze–thaw cycles. Pinhão starch exhibited a higher viscosity peak and breakdown, along with a lower final viscosity and setback, compared to guabiju and uvaia starches. The significantly different pasting properties influenced the porous microstructure, water absorption (p-value: 0.01), and resistance of the hydrogels (p-value: 0.01). The guabiju starch hydrogels showed a uniform pore structure without cavities, whereas pinhão and uvaia starch hydrogels exhibited agglomerated and spongy pore structures. Furthermore, the guabiju starch hydrogel demonstrated the lowest water absorption (4.56 g/g) and the highest compression resistance (1448.50 g) among all the studied starch hydrogels. In contrast, the pinhão starch hydrogel showed the highest water absorption (7.43 g/; p-value: 0.01) among all studied starch hydrogels. The hardness of uvaia starch hydrogel did not differ significantly from the guabiju and pinhão starch hydrogel. The different non-conventional starches reveal important variations in the hydrogels characteristics. This provides insights into how amylose and amylopectin interact and present alternatives for using these unique starch-based hydrogels in diverse applications.

Comparative studies of starch blends on the properties of PVA films

This research studied the effects of pregelatinized starch (PST) and hydrolyzed starch (HST) at various contents with 20 phr glycerol on the properties of polyvinyl alcohol (PVA) film. FTIR analysis showed that the increase of HST preferably interacted with the hydroxyl (OH) groups and CH molecules, while the interaction of hydrogen bonding with PST interacted with OH groups of PVA, but did not affect CH stretching molecules. The blend with HST possessed lower overall thermal degradation than the blend with PST. Tensile strength by blending with PST increased from 14 MPa to 30 MPa, while the elongation at break decreased by a factor of two. On the other hand, elongation at break of the blends with HST improved from 300 (when no HST) to 350%, and its tensile strength improved slightly only with 10 and 20% blending. Regarding the water-soluble properties, hydrogen bonding interaction of starch, PVA and glycerol showed hardly any effect on the rate of dissolving the blends. However, the chemical structure of starch and the size of molecules, especially in HST dramatically increased the rate of dissolving in water.

Multi-Scale Comparison of Physicochemical Properties, Refined Structures, and Gel Characteristics of a Novel Native Wild Pea Starch with Commercial Pea and Mung Bean Starch

In the present study, the morphology, refined structure, thermal properties, and dynamic rheological, texture, and digestive properties of common vetch starch, a potential new type of legume starch, were systematically investigated, and compared with commercially available pea and mung bean starch. The results showed that the composition and chemical structure of common vetch starch were similar to the pea and mung bean starch. However, the amylose content (35.69), A-chain proportion (37.62), and relative crystallinity (34.16) of common vetch starch were higher, and the particle size and molecular weight (44,042 kDa) were larger. The value of pasting properties and enthalpy change (ΔH) of gelatinization of common vetch starch was lower and higher than mung bean and pea starch, respectively, and a lower swelling power and pasting index indicate that common vetch starch had higher hot-paste and cold-paste stability. In addition, common vetch starch gel exhibited good rheology, cohesiveness, and anti-digestive properties. These results provide new insights into the broader application of common vetch starch.

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.