Surface Properties of Heat‐Induced Soluble Soy Protein Aggregates of Different Molecular Masses

Suspensions (2% and 5%, w/v) of soy protein isolate (SPI) were heated at 80, 90, or 100 °C for different time periods to produce soluble aggregates of different molecular sizes to investigate the relationship between particle size and surface properties (emulsions and foams). Soluble aggregates generated in these model systems were characterized by gel permeation chromatography and sodium dodecyl sulfate‐polyacrylamide gel electrophoresis. Heat treatment increased surface hydrophobicity, induced SPI aggregation via hydrophobic interaction and disulfide bonds, and formed soluble aggregates of different sizes. Heating of 5% SPI always promoted large‐size aggregate (LA; >1000 kDa) formation irrespective of temperature, whereas the aggregate size distribution in 2% SPI was temperature dependent: the LA fraction progressively rose with temperature (80→90→100 °C), corresponding to the attenuation of medium‐size aggregates (MA; 670 to 1000 kDa) initially abundant at 80 °C. Heated SPI with abundant LA (>50%) promoted foam stability. LA also exhibited excellent emulsifying activity and stabilized emulsions by promoting the formation of small oil droplets covered with a thick interfacial protein layer. However, despite a similar influence on emulsion stability, MA enhanced foaming capacity but were less capable of stabilizing emulsions than LA. The functionality variation between heated SPI samples is clearly related to the distribution of aggregates that differ in molecular size and surface activity. The findings may encourage further research to develop functional SPI aggregates for various commercial applications.     

The use of spray drying technology to reduce bitter taste of casein hydrolysate

The utilization of protein hydrolysates in food systems is frequently hindered due to their bitterness and hygroscopicity. Spray drying technology could be an alternative for reducing these problems. The aim of this work was to reduce or to mask the casein hydrolysate bitter taste using spray drying and mixtures of gelatin and soy protein isolate (SPI) as carriers. Six formulations were studied: three with 20% of hydrolysate and 80% of mixture (gelatine/SPI at proportions of 50/50, 40/60 and 60/40%) and three with 30% of hydrolysate and 70% of mixture (gelatine/SPI at proportions of 50/50, 40/60 and 60/40%). The spray-dried formulations were evaluated by SEM, hygroscopicity, thermal behavior (DSC), dissolution, and bitter taste, by a trained sensory panel using a paired-comparison test (free samples vs. spray-dried samples); all samples were presented in powder form. SEM analysis showed mostly spherically shaped particles, with many concavities and some particles with pores. All formulations were oil and water compatible and showed lower hygroscopicity values than free casein hydrolysate. At Aw 0.83, the free hydrolysate showed Tg about 25 °C lower than the formulations, indicating that the formulations may be more stable at Aw ≥ 0.65 since the glass transition should be prevented. The sensory panel found the formulations, tasted in the powder form, to be less bitter (P < 0.05) than the free casein hydrolysate. These results indicated that spray drying of casein hydrolysate with mixtures of gelatin and SPI was successful to attenuate the bitterness of casein hydrolysate. Thus, spray drying widens the possibilities of application of casein hydrolysates.     

Processing, Packaging, and Storage Effects on Quality of Freeze-Dried Strawberries

Water sorption isotherms of freeze-dried strawberries were determined using the interval sorption technique. The surface temperature during freeze-drying (from 20°C to 60°C) affected the hygroscopicity of the strawberries, particularly below 0.40 a_w. Over 1 yr, quality changes in dried strawberries were evaluated by sensory analysis at 3-month intervals. Crushing before drying and low processing temperatures improved sensory quality of dried strawberries and vacuum packaging improved storage stability.     

Sorption behavior,thermodynamic properties and storage stability of ready-to-eat Elephant Foot Yam (<Emphasis Type="Italic">Amorphophallus</Emphasis> spp.) product: physic-chemical properties,minerals, total dietary fiber and phenolic content of stored product

The effect of osmotic dehydration in sucrose solution followed by convective dehydration on sorption isotherms and storage stability of elephant foot yam was evaluated in the present work. The equilibrium moisture content of un-treated (Hot-air-dried) and pre-treated (Osmo-air-dried) samples were determined by static gravimetric method at different temperatures (20, 30, 40, and 50?°C) and relative humidities (11–90?%). The curves obtained for sorption can be considered as type-II according to Brunauer–Emmett–Teller (BET) classification. The higher values of net-isosteric heat of sorption and heat of vaporization was observed for un-treated samples. i.e. 6.82–14.79 and 2978.28–3548.68 kJ/kmol as compared to pre-treated samples. i.e. 6.72–14.09 and 2858.33–3315.85 kJ/kmol, respectively and decreased with increase in moisture content. The experimental data revealed that enthalpy–entropy compensation theory was satisfactorily applicable to the moisture sorption behavior of the un-treated and pre-treated EFY samples. Mineral contents of fresh EFY product viz. magnesium, potassium and calcium were 190?±?1.0, 515?±?2.5 and 214?±?2.08 mg/100g, respectively. After 6 months of storage change in minerals was not significant, whereas significant increase in dietary fiber (15.95?±?0.76?19.68?±?0.45 g/100g) and slight but significant reduction in phenolic content (49.97?±?0.76–46.81?±?0.60 mgGAE/g extract) was observed.     

Moisture adsorption isotherms of yew wood (<Emphasis Type="Italic">Taxus baccata</Emphasis> L.)

Adsorption isotherm was obtained to assess the hygroscopicity of yew wood using the Hailwood-Horrobin sorption theory. Yew wood showed very low EMC values in the whole range of relative humidities. An interesting point was that the adsorption isotherms of the yew wood were almost identical to that of pine wood modified with 15.8% acetic anhydride.     

Improvement in emulsifying properties of soy protein isolate by conjugation with maltodextrin using high‐temperature,short‐time dry‐heating Maillard reaction

Soy protein isolate (SPI)–maltodextrin (MD) conjugates were synthesised using Maillard reaction under high‐temperature (90, 115 and 140 °C), short‐time (2 h) dry‐heating conditions. The loss of free amino groups in proteins and sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS‐PAGE) profile confirmed that SPI‐MD conjugates were formed and higher dry‐heated temperatures could increase the glycosylation degree. The emulsifying properties of SPI and SPI‐MD conjugates were evaluated in oil‐in‐water emulsions. The emulsions stabilised with SPI‐MD conjugates synthesised at 140 °C exhibited higher emulsifying stability and excellent storage stability against pH, ionic strength and thermal treatment compared with those synthesised at 90 °C, 115 °C and SPI stabilised emulsions. This might be due to a greater proportion of conjugated MD in SPI‐MD conjugates synthesised at 140 °C because of the higher glycosylation degree, and more conjugated MD on the droplet surface could provide steric effect and enhance the stability of the droplets in the emulsions.     

Functionality of Milk Powders and Milk‐Based Powders for End Use Applications—A Review

Abstract: Newer variants of milk powders and milk‐based powders are being produced are looking for prospective end users. Powders possess physical and functional properties that are of significance in its usage notably powder structure, particle size distribution, powder density, bulk density, particle density, occluded air, interstitial air, flowability, rehydration (wettability, sinkability, dispersibility, solubility), hygroscopicity, heat stability, emulsifying ability, water activity, stickiness, caking, and others. Some of the functional properties of significance to milk powders and milk‐based powders are discussed in this review. Applications with regard to specific milk powders for reconstituted cheese making, coffee creamers, and those suited for milk chocolate and for the baking industry are described.     

Moisture adsorption isotherms of two esterified Greek hardwoods

Two Greek hardwoods (Ulmus montana and Acer pseudoplatanus), were esterified with acetic and maleic anhydride and studied for moisture adsorption behaviour. The sorption isotherms for untreated and chemically modified wood were analysed using the Hailwood-Horrobin model. The experimental analysis of the sorption isotherms showed that esterification affects both total, polymolecular and monomolecular sorption. Acetic anhydride treatment was found more effective in reducing the hygroscopicity of wood compared to maleic anhydride treatment at comparable weight percentage gain, reflecting probably the strong ester bonds between acetic anhydride and wood. Identical e.m.c values were attained in both types of sorption for maple and elm wood, at comparable weight percentage gain, not only for the unmodified samples but for the modified ones as well.     

Production and properties of casein hydrolysate microencapsulated by spray drying with soybean protein isolate

The aim of this work was to encapsulate casein hydrolysate by spray drying with soybean protein isolate (SPI) as wall material to attenuate the bitter taste of that product. Two treatments were prepared: both with 12 g/100 g solids and containing either two proportions of SPI: hydrolysate (70:30 and 80:20), called M1 and M2, respectively. The samples were evaluated for morphological characteristics (SEM), particle size, hygroscopicity, solubility, hydrophobicity, thermal behavior and bitter taste with a trained sensory panel using a paired-comparison test (non-encapsulated samples vs. encapsulated samples). Microcapsules had a continuous wall, many concavities, and no porosity. Treatments M1 and M2 presented average particle sizes of 11.32 and 9.18 μm, respectively. The wall material and/or the microencapsulation raised the hygroscopicity of the hydrolysate since the free hydrolysate had hygroscopicity of 53 g of water/100 g of solids and M1 and M2 had 106.99 and 102.19 g of water/100 g of solids, respectively. However, the hydrophobicity decreases, the absence of a peak in encapsulated hydrolysates, and the results of the panel sensory test considering the encapsulated samples less bitter (p < 0.05) than the non-encapsulated, showed that spray drying with SPI was an efficient method for microencapsulation and attenuation of the bitter taste of the casein hydrolysate.     

Influence of protein concentration on surface composition and physico-chemical properties of spray-dried milk protein concentrate powders

Surface composition, moisture sorption behaviour and glass–rubber transition temperature (T_gr) were determined for spray-dried milk protein concentrate (MPC) powders over a range of protein contents (35–86 g 100 g⁻¹). Surface characterisation of MPC powders indicated that fat and protein were preferentially located on the surface of the powder particles, whereas lactose was located predominantly in the bulk. Moisture sorption analysis at 25 °C showed that MPC35 exhibited lactose crystallisation, whereas powders with higher protein contents did not and continually absorbed moisture upon humidification up to 90% RH. The GAB equation, fitted to sorption isotherms of MPCs, gave increases in monolayer moisture value (m_m) with protein content. T_gr, measured with a rheometer, decreased significantly (P < 0.05) with increasing water content and increased with increasing protein content (P < 0.05). In conclusion, increasing protein concentration of MPCs resulted in altered surface composition and increased m_m value and T_gr values.     

Enhanced chemical stability,chromatic properties and regeneration of betalains in Rivina humilis L. berry juice

Betalains are hydrophilic colorants containing chromophore betalamic acid. Owing to poor stability, its usage is limited to low acidic short shelf-life, and frozen foods. In this report, effect of metals (inorganic Se⁴⁺, Zn²⁺, and Cu²⁺) on stability of betalains in Rivina humilis L. berry juice (RBJ) was studied in presence of 10 and 40 μg metal/mL with/without ascorbic acid (AA; 0.25 and 0.5 g/100 mL). Se bleached RBJ betacyanins mildly, whereas Zn, and Cu bleached the pigments significantly. AA protected the pigments from metal-induced bleaching, and stabilizing effect of 0.25 g AA/100 mL was higher (P < 0.05) than 0.5 g AA/100 mL. AA (0.25 g/100 mL) + Se (40 μg/mL) enhanced (five-fold) the half-life time of betacyanins. RBJ betacyanins degraded up to 95% and 96% on treatment for 36 min at 90 °C and storage for 48 days at 25 °C, respectively, whereas only 15% pigment was lost on storage (5 °C, 90 days). AA (0.25 g/100 mL) + Se (40 μg/mL) regenerated the pigments on storage at 5 °C after thermal degradation. Color values of AA (0.25 g/100 mL) + Se (40 μg/mL) containing samples indicated an orange tinge, whereas other samples turned brown yellow after thermal treatment.     

Effect of hydroxypropyl methylcellulose,whey protein concentrate and soy protein isolate enrichment on characteristics of gluten‐free rice dough and bread

Due to a lack of gluten, rice dough needed some additives to improve its properties. This study aimed to investigate effect of hydroxypropyl methylcellulose (HPMC), whey protein concentrate (WPC) and soy protein isolate (SPI) on rice dough and bread. HPMC increased water absorption of the rice dough (P ≤ 0.05). Adding SPI (2–4 g per 100 g flour) together with HPMC tended to increase stability time and reduce tolerance index. During fermentation, HPMC increased maximum dough height, while SPI increased final dough height (P ≤ 0.05). All addition improved tan δ (G″/G′) to be comparable to the wheat dough, but it could not improve gas production and retention. Therefore, specific volume, springiness, cohesiveness and chewiness of rice bread were lower than those of wheat bread (P ≤ 0.05). Percentage of small pores in rice bread was reduced to be comparable to wheat bread, by adding WPC. All addition could improve porosity of the rice bread.     

Interaction of mulberry anthocyanins with soybean protein isolate: effect on the stability of anthocyanins and protein in vitro digestion characteristics

The interactions of anthocyanins and proteins might mutually influence each other on the physicochemical and functional properties. In this study, the interaction mechanism of soybean protein isolate (SPI) with mulberry anthocyanins (MA), and its effect on the thermal stability of anthocyanins and protein subunits’ digestibility were investigated through multiple spectroscopies and in vitro gastrointestinal models. Results showed that cyanidin-3-O-glucoside (C3G), the main anthocyanin monomer in MA, could bind to SPI through hydrophobic interactions, resulting in static fluorescence quenching of SPI. The secondary structure of SPI changed by binding to C3G, with an increase of β-sheet and a decrease of α-helix and random coil. The formation of the SPI-MA complexes improved the thermal stability of MA at 353 K, while, no significant protection occurred during heating at 368 K. Complexation with MA promoted the digestibility of SPI by pepsin, especially the α′ and α subunits of β-conglycinin and the basic subunit of glycinin, and slightly delayed the digestibility of SPI under intestinal fluid. These results provide an in-depth understanding of the influence of the protein-anthocyanin interactions on the stability of anthocyanins and protein digestibility.     

Moisture sorption and the applicability of the Brunauer-Emmett-Teller equation for some dry food products

Moisture sorption studies have been carried out on 16 low moisture foodstuffs at 27°C and based on the major type of constituent, viz starch, fat, protein and high hygroscopicity, the isotherms have been divided into four groups. The moisture sorption behaviour over 0.06-0.92 water activity of the foods has indicated that the Brunauer-Emmett-Teller (BET) equation is applicable generally up to 0.6 water activity. The storage stability aspects of foodstuffs with respect to water activity have been summarised.     

Characterisation of curcumin‐loaded proliposomes produced by coating of micronised sucrose and hydration of phospholipid powders to obtain multilamellar liposomes

The objective of this study was to obtain and characterise curcumin‐loaded proliposomes by the method of coating of micronised sucrose. Proliposomes incorporating curcumin were characterised in terms of coating, morphology, crystallinity, solubility and water sorption. The powders showed a good capacity to preserve curcumin, as after 60 days of storage about 80% of the initial amount of curcumin was preserved. The water adsorption on the proliposomes was very low, as was the hygroscopicity (3.4%). The evaluation of the capacity of the multilamellar liposomes produced by the hydration of phospholipid powders to preserve encapsulated curcumin was assessed. Liposome dispersions were produced with different thickeners, and the best results of average size (around 800 nm) and curcumin preservation (72% after 30 days of storage) were obtained with xanthan gum and guar gum. These results evidenced the coating of micronised sucrose is a promising technique to produce liposomes to be incorporated into food.     

Sorption isotherms and thermodynamic properties of freeze‐dried colostral whey powders with different additives

Moisture adsorption isotherms of colostral whey (CW) powders with different additives (maltodextrin and sucrose) were determined using gravimetric static method at 15–35 °C in the water activity range of 0.067–0.76. The moisture adsorption isotherms obtained were typical sigmoid curves, and the modified‐Halsey and Guggenheim–Anderson–de Boer (GAB) equations gave the best fit to experimental data among five well‐known equations. Addition with maltodextrin into CW powders could effectively decrease equilibrium moisture content (EMC), whereas addition with sucrose increased EMC in the water activity of 0.43–0.76 at 15 and 25 °C and in the water activity of 0.21–0.76 at 35 °C, respectively. Thermodynamic properties including net isosteric heat of sorption and differential entropy were determined from adsorption data using Clausius–Clapeyron equation. The results showed that net isosteric heat of sorption of all the samples decreased exponentially with increasing EMC. Enthalpy–entropy compensation theory was applicable for adsorption process of all the samples, and the adsorption processes were enthalpy‐driven.     

磷酸盐-大豆分离蛋白联合处理对草鱼肌原纤维蛋白凝胶化的影响

为探讨磷酸盐(三聚磷酸钠、六偏磷酸钠、焦磷酸钠(tetrasodium pyrophosphate,TSPP))和大豆分离蛋白(soy protein isolate,SPI)对草鱼肌原纤维蛋白凝胶化的影响,采用热处理方法,将不同质量浓度的磷酸盐、SPI与草鱼肌原纤维蛋白混合制成凝胶.用黏度、嫩度、持水性、显微结构和粗...     

Oxidative stability of alpha‐linolenic acid (ω‐3) in flaxseed oil microcapsules fortified market milk

The oxidative stability of α‐linolenic acid (ALA) was investigated in market milk fortified with flaxseed oil microcapsules. Milk was fortified at levels of 1, 2 and 3 g/100 mL using flaxseed oil powder, and optimised on the basis of sensory scores. No significant difference was observed between the control, 1 and 2 g/100 mL fortified milk samples. Therefore, 2 g/100 mL fortified milk was further evaluated for oxidative stability, fatty acids profile and sensory acceptability during 5 days of storage. The fortified milk was oxidatively stable and sensorially acceptable, retaining ~10.35% ALA, which indicated that 250 mL of milk could meet ~46% of the RDA for ω‐3 fatty acids.     

Predicting suitable storage conditions for spray-dried microcapsules formed with different biopolymer matrices

Canola oil (CO)-in-soy protein isolate (SPI, 12.5 g per 100 ml of solution), CO-in-whey protein concentrate (WPC, 30 g per 100 ml of solution) and CO-in-mesquite gum (MG, 30 g per 100 ml of solution) emulsions were obtained (all with CO to biopolymers solids ratio of 25 g of canola oil per 100 g of wall material), spray dried and stored at water activities (a_w) of 0.12–0.89 at temperatures of 15, 25 and 35 °C. The powders adsorption isotherms experimental data were fitted to the GAB model. Their differential and integral enthalpies and entropies were estimated. The microcapsules point of minimum integral entropy (maximum stability) kept at 25 °C occurred at 10.40 g water per 100 g of dry solids (a_w of 0.55) for MG, 10.59 g water per 100 g of dry solids (a_w of 0.68) for SPI, and 6.38 g water per 100 g of dry solids (a_w of 0.46) for WPC. The integral enthalpy–entropy compensation indicated that the water vapour adsorption was controlled by entropic mechanisms at low a_w, but by enthalpic mechanisms at high a_w.     

改性纳米TiO2-大豆分离蛋白抑菌保鲜膜的制备及其性能

选取表面改性的纳米TiO2制备大豆分离蛋白（soy protein isolate,SPI）膜,以复合膜的抗拉强度、断裂伸长率、水蒸气透过率、透光性、透氧性、透二氧化碳性为评价指标,通过单因素试验和正交试验优化制膜最佳工艺。结果表明,复合膜的最佳成膜工艺条件为SPI添加量4.5?g/100?mL、改性TiO2添加量2.0?g/100?mL、甘油添加量1.5?g/100?mL,其接触角为115.3°。傅里叶变换红外光谱仪实验结果表明,改性纳米TiO2-SPI复合膜与纳米TiO2-SPI复合膜、普通SPI膜在4 000～600 cm－1波数范围内呈现出相似的红外光谱,且由扫描电子显微镜以及原子力显微镜扫描结果可以看出,与纳米TiO2-SPI复合膜及普通SPI膜相比,改性纳米TiO2-SPI复合膜表面更为致密平整,表面性能表现更佳,改性纳米TiO2-SPI复合膜的结构性质要优于纳米TiO2-SPI复合膜及普通SPI膜。当改性TiO2添加量为2?g/100?mL、365?nm波长紫外灯照射6?h时,复合膜对大肠杆菌和李斯特菌的抑菌性能最强,抑菌率达到91.14%和92.81%。改性纳米TiO2-SPI复合膜具有一定的机械性能和良好的抑菌性能,在食品包装应用方面具有巨大潜力。