Effects of Lactobacillus plantarum fermentation on the structure, physicochemical properties, and digestibility of foxtail millet starches.

This study investigated the effects of Lactobacillus plantarum fermentation on the structural, physicochemical, and digestive properties of foxtail millet starches. The fermented starch granules formed a structure with honeycomb-like dents, uneven pores, and reduced particle size. As the fermentation time extended, the amylose content of waxy (0.88 %) and non-waxy (33.71 %) foxtail millet starches decreased to the minimum value at 24 h (0.59 % and 29.19 %, respectively), and then increased to 0.85 % and 31.87 % at 72 h, respectively. Both native and fermented foxtail millet starches exhibited an A-type crystal structure. Compared with native samples, the fermented samples performed enhanced proportion of short-branched chain, crystallinity, and short-range ordered degree. After fermentation for 24 h, the solubility, adsorption capacity, and pasting viscosity of foxtail millet starches improved, whereas the swelling power, pasting temperature, breakdown, setback, and degree of retrogradation reduced. Additionally, fermentation increased the transition temperatures, enthalpy, and digestibility. Overall, Lactobacillus plantarum fermentation is considered a competent choice to regulate the characteristics of foxtail millet starch.

Pickering emulsions stabilized by starch nanocrystals prepared from various crystalline starches by ultrasonic assisted acetic acid: Stability and delivery of curcumin.

Ultrasonic assisted acetic acid hydrolysis was applied to prepare starch nanocrystals (SNCs) from native starches with different crystalline structures (A, B, and C types). The structure properties, morphology, Pickering emulsion stability and curcumin deliver capacity of both SNCs and native starches were investigated and compared. Compared with native starches, SNCs showed smaller size and higher crystallinity. The size of SNCs varied with different crystalline types, with C-type starch exhibiting the smallest SNCs (107.4 nm), followed by A-type (113.8 nm), and B-type displaying the largest particle size (149.0 nm). SNCs-Pickering emulsion showed enhanced stability with smaller emulsion droplets, higher static stability, and denser oil/water interface. SNCs-Pickering emulsions displayed higher curcumin loading efficiency (53.53 %-61.41 %) compared with native starch-Pickering emulsions (13.93 %-19.73 %). During in vitro digestion, SNCs-Pickering emulsions proved to be more proficient in protecting and prolonging the biological activity of curcumin due to their smaller size and better interfacial properties. These findings demonstrated the potential of SNCs for application in Pickering emulsion and delivery of bioactive components.

High-efficiency preparation of starch nanocrystals with small size and high crystallinity by ethanol-acid penetration and dry-heating pretreatment.

Ethanol-acid penetration and drying-heating treatment was developed to shorten the preparation time and improve the quality of starch nanocrystals (SNCs). After treatment by optimized parameters, including 40 % ethanol solution, 10.6 mM chloric acid, and heating time of 1.5 h or 2.0 h, the starches exhibited weakened internal structure and relatively complete crystalline structure. Compared with the regular preparation of only acid hydrolysis, the regular final yield (8.5 % after 5 days) was reached in 48 h and 12 h of the starch heated at 1.5 h and 2.0 h, respectively. The micromorphology, molecular weight, and crystalline structure evaluation demonstrated that the collected nanoparticles were indeed SNCs with smaller size and higher relative crystallinity than regular SNCs. Further analysis found that the SNCs had better crystalline lamellae, higher thermal stability, and lower proportion of phosphorus and sulfur atoms than regular SNCs. This provided a potential method for the high-efficiency preparation of SNCs.

Structural analysis, nutritional evaluation, and flavor characterization of parched rice made from proso millet.

This study investigated the structure and quality characteristics of hard and crispy parched rice obtained from raw proso millet through steaming, roasting, and milling. Results showed that thermal treatment disrupted the structure of samples and transformed the crystal from A-type in raw proso to V-type in parched rice. Rheological and thermodynamic analyses revealed that thermal treatment reduced the stability of parched rice. Gelatinization tests demonstrated that the parched rice was easier to gelatinize and had a lower viscosity. The digestibility of hard parched rice and crispy parched rice improved, with rapidly digestible starch content increasing by 73.62% and 76.95%, respectively, compared with that of raw proso millet. Headspace solid-phase microextraction/gas chromatography-mass spectrometry results further indicated that thermal treatment enhanced the flavor substances of parched rice. These findings demonstrated the unique properties of parched rice and supported its production and processing as a whole grain.

A new sight separation for collecting starch nanocrystals with small size and high crystallinity based on the hydrolysis mechanism.

To prevent starch nanocrystals (SNCs) that are generated at an early stage from being hydrolyzed excessively, this study proposed a new separation method, named "neutral dispersion and acidic precipitation." SNCs were prepared from waxy potato starch by sulfuric acid hydrolysis. Based on the results of kinetics and molecular weight, the hydrolysis was divided into three stages, e.g., rapid (initial 1 day), medium (subsequent 1 day) and slow stage (2-5 days). The rapid and medium stages were related to the degradation of amorphous region in starch, and the slow stage mainly referred to SNC release. Therefore, the method was developed to separate SNCs at the slow stage. After centrifugation at 6000 rpm, large particles were removed from the SNC suspension under pH 7. The SNCs with small average size and crystallite size, high relative crystallinity (RC), and high dispersion stability in the supernatant were retained and were then precipitated entirely under pH 5, because pH 5 led to the reduction of dispersion stability of SNCs. Meanwhile, the hydrothermal and dry-thermal stability of separated SNCs were significantly promoted. The separation method has the potential in SNC preparation for increasing the yield and collecting products with small size and high RC.

Characterization of quinoa starch nanoparticles as a stabilizer for oil in water Pickering emulsion.

Quinoa starch nanoparticles (QSNPs) prepared by nanoprecipitation had a uniform particle size of 191.20 nm. QSNPs with amorphous crystalline structure had greater contact angle than QS with orthorhombic crystalline structure, which can therefore be utilized to stabilize Pickering emulsions. QSNPs-based Pickering emulsions prepared by suitable formulations (QSNPs concentration of 2.0-2.5 %, oil volume fraction of 0.33-0.67) exhibited good stability against pH of 3-9 and ionic strength of 0-200 mM. The oxidative stability of the emulsions increased with increasing starch concentration and ionic strength. Microstructural and rheological results indicated that the structure of the starch interfacial film and the thickening effect of the water phase affected the emulsion stability. The emulsion had excellent freeze-thaw stability and can be produced as a re-dispersible dry emulsion using the freeze-drying technique. These results implied that the QSNPs had great potential for application in the preparation of Pickering emulsions.

Structural, functional properties of protein and characteristics of tofu from small-seeded soybeans grown in the Loess Plateau of China.

The structural, functional properties of protein isolated from small-seeded soybeans were investigated and characteristics of tofu were studied. Small-seeded soybean protein had obvious α', α, ß, acidic and basic subunits bands and two endothermic peaks (76.02-76.63℃ and 91.94-94.25℃). Small-seeded black soybean protein isolates (SBSPI) had more ß-sheet (31.90-33.54%) structure, while small-seeded yellow soybean protein isolates (SYSPI) had more α-helix (18.89-20.72%) structure. SYSPI had higher fluorescence intensity (839.10-847.80) than SBSPI (482.70-565.10). SBSPI exhibited higher surface hydrophobicity (939.51-1252.75) and water absorption capacity (8.07-8.50 g/g). Tofu made from small-seeded yellow soybeans had higher yield (549.46-560.23 g/100 g soybean) and was brighter (L*, 74.61-77.48) and more yellowish (b*, 14.83-14.95) in color. Tofu made from Fugu small-seeded black soybean (FGSBS) had the highest hardness (178.52 g), adhesiveness (-25.77 g.sec), chewiness (87.45 g) and resilience (0.26), signifying a more compact structure.

Comparison of properties and application of starch nanoparticles optimized prepared from different crystalline starches.

Starch nanoparticles (SNPs) were produced by nanoprecipitation combined with ultrasonication with the use of different starches (corn, potato and sago starch) and used to stabilize Pickering emulsions. The orthogonal experiment was used to optimize preparation conditions of gelatinization pretreatment duration of 30 min, ultrasonic power of 600 W, and ultrasonic time of 40 min. Compared with native starch, the SNPs were spherical in shape and displayed a V-type crystalline structure with low relative crystallinity and higher degree of double-helix. Compared with native starch-Pickering emulsion, the SNP-Pickering emulsion had a smaller droplet size, more uniform distribution, clearer oil/water interface, and higher static stability of droplets. The sago SNP-Pickering emulsion had the great gelatinous structure and emulsion stability. In addition, the SNP-Pickering emulsion had the better loading efficiency and controlled release performance of curcumin. Meanwhile, the bioavailability of curcumin in sago SNP-Pickering emulsion was highest.

Formation mechanism of starch nanocrystals from waxy rice starch and their separation by differential centrifugation.

Starch nanocrystals (SNCs) were prepared from waxy rice starch via sulfuric acid hydrolysis. The objective focused on the following: i) the hydrolysis kinetics and structural properties of SNCs; ii) the effects of differential centrifugation on the yield and size distribution of SNCs. The hydrolysis was divided into a rapid hydrolysis stage in the initial two days and a slow hydrolysis stage after two days. During the two-day hydrolysis, the average diameter of SNCs reached 244 nm. After two days of hydrolysis, the degree of crystallinity, crystallite size, and melting temperature and enthalpy increased. The proportion of A-branched chains decreased, whereas the proportion of B1-branched chains and molecular weight did not change considerably. Thus, the reaction in the slow hydrolysis stage could be considered as the surface modification and gradual release of SNCs. Furthermore, SNCs with a small size and high charge density could be used for differential centrifugation.

Structure, physicochemical, functional and in vitro digestibility properties of non-waxy and waxy proso millet starches.

The structural, physicochemical, gel textural, rheological, and in vitro digestibility properties as well as their relationships of non-waxy proso millet starch (NPMS) and waxy proso millet starch (WPMS) were evaluated by taking normal corn starch (CS) and potato starch (PS) as controls. Proso millet starch was mostly polygonal or spherical, with an A-type crystalline structure. Proso millet starch contained more short-branched chains (DP 6-24) compared with CS and PS. WPMS possessed higher crystallinity and more short-range ordered structures than NPMS. NPMS displayed higher pasting temperature, retrogradation rate and shear thinning degree, and lower gelatinization temperature and enthalpy than WPMS. The hardness and chewiness of starch gel formed by NPMS were higher than those of WPMS. All starch samples exhibited shear thinning behavior in the steady-flow test and typical elastic solid behavior in the dynamic rheological test. Moreover, NPMS was considered a potential formula for functional foods, with its lower rapidly digestible starch (RDS) and higher resistant starch (RS) contents than WPMS, CS, and PS. This paper revealed the influence of amylose content and structure on the physicochemical properties of different proso millet starch.

Effects of morphology and rheology of starch nanoparticles prepared from various coarse cereals on emulsifying ability.

Starch nanoparticles (SNPs) were prepared by rapid nanoprecipitation using coarse cereal starches, including quinoa, waxy proso millet, non-waxy proso millet, and maize starches (amylose content, 2.20 %-13.96 %). Morphology and dynamic light scattering analyses showed that the particle size of SNPs ranged from 190.35 nm to 310.25 nm. Ultrasonic pretreatment reduced the particle size. Quinoa and waxy proso millet SNPs swelled to flocculent, whereas non-waxy proso millet and maize SNPs showed spherical particles. Quinoa and waxy proso millet SNPs did not completely nucleate after nanoprecipitation. Quinoa SNPs formed a stable network in water, showing great viscoelastic behavior with higher G' and G''. Subsequently, the SNPs suspensions were used to prepare emulsions. The quinoa SNPs-based Pickering emulsion was the smallest and most uniform (12.96 µm), with great stability. These results suggested that the quinoa SNPs suspension with a stable network could be used as an efficient emulsifier for stabilizing Pickering emulsions.

Structural, physicochemical and rheological properties of starches isolated from banana varieties (Musa spp.).

Banana starches were isolated from five banana varieties in Tanzania to analyze the proximate composition, structure, physicochemical and rheological properties. The amylose content of banana starches was 29.92 ± 0.17 %-39.50 ± 0.08 % and the resistant starch content of cooked banana starches ranged from 44.74 ± 1.72 % to 55.43 ± 1.52 %. Banana starch granules presented irregular shapes with particle size of 21.73 to 24.67 µm and showed B-type or C-type crystalline patterns with crystallinity of 36.69 % to 41.83 %. The solubility and the swelling power were 2.5 ± 0.42 %-4.4 ± 0.57 % and 11.27 ± 0.04 %-12.48 ± 0.71 %, respectively. Mzuzu and Malindi starches possessed lower gelatinization temperature. The high gelatinization peak viscosity (2248 ± 67-2897 ± 71 cP), low breakdown (556 ± 7-960 ± 41 cP) and low setback (583 ± 29-864 ± 118 cP) indicated banana starch could replace chemically cross-linked starch for applications that require stable viscosity. The rheological analysis showed that banana starches exhibited shear thinning behavior and had great processing adaptability. The results all above will provide basic data for the development and utilization of banana starch.

Optimization of Corn Resistant Starch Preparation by Dual Enzymatic Modification Using Response Surface Methodology and Its Physicochemical Characterization.

Corn starch was dually modified using thermostable α-amylase and pullulanase to prepare resistant starch (RS). The concentration of starch liquid, the amount of added thermostable α-amylase, the duration of enzymatic hydrolysis and the amount of added pullulanase were optimized using RSM to increase RS content of the treated sample. The optimum pretreatment conditions were 15% starch liquid, 3 U/g thermostable α-amylase, 35 min of enzymatic hydrolysis and 8 U/g pullulanase. The maximum RS content of 10.75% was obtained, and this value was significantly higher than that of native corn starch. The degree of polymerization (DP) of the enzyme-modified starch decreased compared with that of native starch. The scanning electron microscopy (SEM) and differential scanning calorimetry (DSC) were performed to assess structural changes in native and pretreated starch. The effect of dual enzyme pretreatment on the structure and properties of corn starch was significant. Unlike the untreated one, the pretreated corn starch showed clear pores and cracks. Significant differences in RS contents and structural characterization between starch pretreated and untreated with dual enzymes demonstrated that the dual enzyme modification of corn was effective in enhancing RS contents.

Preparation and characterization of quinoa starch nanoparticles as quercetin carriers.

Quinoa starch nanoparticles (QSNPs) prepared by nanoprecipitation method under the optimal condition was developed as a carrier for quercetin. The QSNPs prepared under the optimal condition (90 DMSO/H2O ratio, 10 ethanol/solvent ratio, and ultrasonic oscillation dispersion mode) had the smallest particle size and polymer dispersity index through full factorial design. Compared with maize starch nanoparticles (MSNPs), QSNPs exhibited a smaller particle size of 166.25 nm and a higher loading capacity of 26.62%. Starch nanoparticles (SNPs) interacted with quercetin through hydrogen bonding. V-type crystal structures of SNPs were disappeared and their crystallinity increased after loading with quercetin. QSNPs was more effective in protecting and prolonging quercetin bioactivity because of their small particle sizes and high loading capacities. This study will be useful for preparing starch-based carrier used to load sensitive bioactive compounds.

Functional Properties and Structural Characteristics of Starch-Fatty Acid Complexes Prepared at High Temperature.

The effects of fatty acid type (myristic, palmitic, stearic, oleic, linoleic, and linolenic acid) on the characteristics of starch-lipid complexes under high temperature were investigated. Fatty acids with a shorter carbon chain or a greater number of double bonds contributed to the formation of V-type starch-lipid complexes. The thermostability of starch-unsaturated fatty acid (UFA) complexes prepared at high temperature was increased compared with those obtained at lower temperature. Resistant starch (RS) contents and melting temperatures had a strong significant positive correlation. Complexes with better thermostability were more resistant to enzymatic hydrolysis. Among them, the starch-stearic acid complexes possessed the highest RS content. The paste of starch-linolenic acid complexes had the lowest internal friction and the strongest thixotropy. The broken of double bonds in UFAs probably accounted for the increased starch-lipid complexes. The crystalline, thermal, rheological, and digestion properties of samples treated at high temperature were significantly affected.

Preparation and identification of antioxidant peptides from cottonseed proteins.

The objective of this study was to investigate the antioxidant properties of cottonseed peptides. Results indicated that cottonseed peptides prepared by enzymatic hydrolysis and microbial fermentation both showed antioxidant properties. The cottonseed protein enzymatic hydrolysate with molecular weight less than 3 kDa exhibited excellent DPPH, ABTS and hydroxyl radical scavenging activity and ferrous ion chelating activity with EC50 values of 0.49 ± 0.02, 2.05 ± 0.02, 2.21 ± 0.12, and 0.99 ± 0.03 mg/mL, respectively. Amino acid composition analysis revealed that cottonseed protein hydrolysates are rich in acidic/basic and aromatic amino acids. In addition, among the 19 identified cottonseed protein-derived peptides, YSNQNGRF had the lowest CDOCKER energy and formed hydrogen bonds with Tyr334, Arg380, Arg415, Ser508, and Ser602, and van der Waals interactions with Asn382, Tyr525, Gln530, and Ser555, which all located in the binding site of Keap1-Nrf2 interaction. These findings suggested that the antioxidant peptides from cottonseed protein had the potential as functional ingredients in foods.

Physicochemical and structural properties of sago starch.

A comprehensive study was conducted to elucidate physicochemical and structural properties of sago starches. Two sago starch granules were oval in shape with an average diameter of 34.41 µm and had C-type polymorph with a crystallinity of about 28.13%. The amylose and resistant starch (RS) contents of two sago starches were higher than those of corn and potato starches. The two sago starches had a large amount of A and B1 chains (DP 6-24) which could form double helix structures. FTIR exhibited that the structure of two sago starches had a lower degree of order. The peak viscosity and breakdown of sago starch 2 were lower than corn starch, and the setback was higher than potato starch. Additionally, sago starches had lower gelatinization enthalpy and higher regeneration tendency. According to rheological results, sago starches showed lower shear thinning degree and thixotropy compared to corn and potato starches. Sago starch 1 gels represented the highest hardness, adhesiveness, springiness and cohesiveness, which could be used as potential food stabilizer. This study revealed the characteristics of two sago starches compared with other starches. The results indicated that the amylose content and amylopectin structures had significant influence on the physicochemical properties of sago starch.

The preparation, formation, fermentability, and applications of resistant starch.

Resistant starch (RS) cannot be digested in the small intestine but can be fermented by microflora in the colon. To meet the demand for RS, effective methods and advanced equipment for preparing RS have emerged, but further development is needed. RS contents are affected by different prepared methods, starch source and certain nutrients such as protein, phenols, and hydrocolloids interacted with RS. As a beneficial fermentation substrate, RS modifies and stabilizes the intestinal flora to balance the intestinal environment and improve intestinal tract health and function. RS is also a kind of ingredient with potential physiological function, even better than that dietary fiber, but also in terms of providing various health benefits. RS has good food-processing characteristics as well and can thus be widely used in the food industry.

Physicochemical and functional properties of protein isolate obtained from cottonseed meal.

To investigate the effect of preparation methods of cottonseed meals on protein properties, the physicochemical and functional properties of proteins isolated from hot-pressed solvent extraction cottonseed meal (HCM), cold-pressed solvent extraction cottonseed meal (CCM) and subcritical fluid extraction cottonseed meal (SCM) were investigated. Cottonseed proteins had two major bands (at about 45 and 50kD), two X-ray diffraction peaks (8.5° and 19.5°) and one endothermic peak (94.31°C-97.72°C). Proteins of HCM showed relatively more ß-sheet (38.3%-40.5%), and less ß-turn (22.2%-25.8%) and α-helix (15.8%-19.5%), indicating the presence of highly denatured protein molecules. Proteins of CCM and SCM exhibited high water/oil absorption capacity, emulsifying abilities, surface hydrophobicity and fluorescence intensity, suggesting that the proteins have potential as functional ingredients in the food industry.

Enzymatic saccharification of high pressure assist-alkali pretreated cotton stalk and structural characterization.

Cotton stalk is a potential biomass for bioethanol production, while the conversion of direct saccharification or biotransformation of cotton stalk is extremely low due to the recalcitrant nature of lignocellulose. To enhance the enzymatic conversion of cotton stalks, the enzymatic saccharification parameters of high pressure assist-alkali pretreatment (HPAP) cotton stalk were optimized in the present study. Results indicated that a maximum reducing sugar yield of 54.7g/100g dry biomass cellulose was achieved at a substrate concentration of 2%, 100rpm agitation, 0.6g/g enzyme loading, 40°C hydrolysis temperature, 50h saccharification time, and pH 5.0. Scanning electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy were used to identify structural changes in native, pretreated biomass and hydrolyzed residues. Structural analysis revealed large part of amorphous cellulose and partial crystalline cellulose in the HPAP cotton stalk were hydrolyzed during enzymatic treatment. HPAP cotton stalk can be used as a potential feed stock for bioethanol production.