Preparation and characterisation of soya milk enriched with isoflavone aglycone fermented by lactic acid bacteria combined with hydrothermal cooking pretreatment

A fermented soya milk (FSM) enriched with isoflavone aglycone (FSM‐SPIA) was prepared from heated soya protein isolate (SPI)‐isoflavone complex. After 48 h of fermentation, FSM‐SPIA contained higher contents of living bacteria, free amino acids and aglycone compared with the FSM of SPI (FSM‐SPI) and the FSM of SPI‐isoflavone complex (FSM‐Mix). In the in‐vitro digestion experiment, FSM‐SPIA showed higher antioxidant capacity and isoflavones (ISO) bioavailability than FSM‐SPI and FSM‐Mix. This was likely due to the soya milk containing a higher level of amino acid, peptides and the presence of soya bean isoflavone. The improved protein digestibility, the interaction and binding ability between proteins and ISO may affect the properties of the protein and the fermented products. The FSM enriched with isoflavone aglycone can be used as a functional fermented drink, as well as an auxiliary food for menopausal women during a specific pathological period.     

The effect of high solid concentrations on enzymatic hydrolysis of soya bean protein isolate and antioxidant activity of the resulting hydrolysates

This study investigated the effect of high solid concentrations on the enzymatic hydrolysis and antioxidant activities of soya bean protein isolate hydrolysates (SPIHs). The soya bean protein isolate at the concentration of 8%, 16%, 24% and 32% was hydrolysed to obtain SPIH with 21.5% degree of hydrolysis (DH), respectively. Results showed that, for the same DH, significant increases in reaction time and decrease in protein recovery were observed as solid concentrations increased. There was no significant difference in molecular weight distribution, but different amino acid compositions in supernatants of SPIH hydrolysed at different solid concentrations. The level of antioxidant amino acids in high solid concentration (32%) was higher than that in low solid concentration group, and antioxidant activity of SPIH increased with the solid concentration increased. Thus, increasing solid concentrations could increase the antioxidant activities and functional properties with low water costs.     

Structural and physicochemical properties of soya bean protein isolate/maltodextrin mixture and glycosylation conjugates

The effect of mixture and conjugation with maltodextrin (MD) in aqueous solution on the structural and physicochemical properties of soya bean protein isolate (SPI) was investigated. Although the mixing of MD would not change the distribution of secondary structure and tertiary conformation of SPI, the protein aggregation was promoted through hydrophobic interaction, which resulted in the decrease in solubility and the improvement of gel strength and water holding capacity (WHC) of SPI/MD mixture. However, glycosylation decreased α-helix and increased β-structure. The bathochromic shift of the fluorescence emission maximum wavelength for SPI/MD conjugates was promoted, resulting in less compact tertiary conformation. These structural modifications might be the reason for the changes in the physicochemical properties of conjugates. After glycosylation, the surface hydrophobicity and solubility were increased, the average particle size was decreased, and the gelation properties were weakened including gel strength and WHC.     

Biochemical,textural and microstructural changes in whole‐soya bean cotyledon sufu during fermentation

This study aims to investigate the nutritional value of sufu and reduce environmental problems caused by okara, which results from the traditional processing method of sufu. The feasibility of the whole‐soya bean cotyledon sufu (WSCS) processing method, which does not produce okara, was investigated. WSCS was prepared by ripening okara‐containing tofu through various hydrolytic enzymes secreted by Actinomucor elegans for 70 days. After fermentation, total nitrogen, amino nitrogen and lipid contents were found to be lower in WSCS than in traditional sufu (TS), whereas contents of reducing sugar, dietary fibre, isoflavone aglycone and soya bean polysaccharide were higher in WSCS than in TS. The hardness, springiness and adhesiveness of WSCS were 249.703 ± 0.500 g, 0.606 ± 0.008 and 8.393 ± 0.032 J, respectively. The corresponding values for TS were 264.863 ± 0.572 g, 0.615 ± 0.007 and 7.516 ± 0.031 J, respectively. In addition, microstructural changes in WSCS and TS during fermentation were observed through scanning electron microscopy. The results from this study may provide a basis for industrial production of WSCS.     

Calcium sulphate‐induced soya bean protein tofu‐type gels: influence of denaturation and particle size

Soya bean protein isolate (SPI) dispersions (7.25%, w/v) were heated at 65, 75, 85 or 90 °C for different time periods to produce SPI aggregates with diverse degrees of denaturation and particle size to investigate the effects on calcium sulphate (CaSO₄)‐induced tofu‐type gel. The results revealed that gel hardness and water‐holding capacity correlated positively with the degree of denaturation of glycinin (11S) and the particle size of the SPI aggregates. The formed gels showed more uniform and denser network structures with increasing degrees of denaturation and particle size of SPI. Hydrophobic interaction was speculated to be the crucial factor for the retention of gels prepared by SPI whose degree of denaturation by 11S was lower than 4.35%. However, disulphide bonds probably played a more important role in the retention of gels generated by SPI with the 11S denaturation degree of >84.47%. Moreover, the bulk density of the protein aggregates might determine the gel structures to a certain extent.     

Physicochemical and sensory characteristics of soya protein isolate hydrolysates with added substrate‐like amino acids

Soya protein isolate (SPI) with or without added substrate‐like amino acid was subject to enzymatic hydrolysis catalysed by commercial proteases (Alcalase 2.4 L, flavourzyme and pancreatin). Addition of a small amount of amino acids (amino acid: SPI = 1: 2500, mol g^?1) during hydrolysis would cause a significantly (P < 0.05) reduced protein recovery, increased degree of hydrolysis, and altered amino acid composition and antioxidant activities of SPI hydrolysates. The SPI hydrolysates prepared with added Asp, Arg or Lys exhibited a higher antioxidant activity than the control. The bitterness of SPI hydrolysates was largely reduced upon addition of Met, Asp or Glu during hydrolysis, whilst the umami taste and mouthfeel‐liking were remarkably increased. Therefore, adding amino acid during hydrolysis is a feasible and beneficial approach to improve both the functional and sensory properties of SPI hydrolysate.     

Effects of β‐glucans on properties of soya bean protein isolate thermal gels

The effects of concentration and molecular weight of oat β‐glucans on properties of soya bean protein isolate (SPI) thermal gels prepared by heating at 90℃for 30 min were investigated. Compared with control (free of β‐glucan) formulations, the presence of β‐glucans (0.5–1.5%, w/v) largely enhanced storage modulus (G′) and texture properties of SPI (12%, w/v) thermal gels measured by dynamic oscillatory rheometry and texture profile analysis, which were developed as increasing β‐glucan concentration and molecular weight. It is possible that β‐glucans could cause the formation of protein aggregates to produce gels through hydrophobic interactions. Mixed gel systems at low ionic strength showed higher G′ resulting from the lower denaturation temperature of SPI, which was beneficial to the formation of gel structure. In addition, although adding a certain amount of β‐glucan into SPI reduced water‐holding capacity of mixed gels, high molecular weight of β‐glucan improved their water‐holding capacity compared to control formulations attributed to the improvement of the structural integrity of the mixed gel network.     

Physicochemical properties of soya bean protein gel prepared by microbial transglutaminase in the presence of okara

The influences of okara on the gelling and secondary protein structure of soya protein isolate (SPI) were investigated. Okara was ultra‐refined by high‐pressure homogenisation. The resulting particle sizes and microscopic morphologies were determined using a laser particle size analyser and a confocal laser scanning microscope, respectively. After okara homogenisation, surface area average particle size (D₃₂) decreased from 49.68 to 23.29 μm and volume average particle size (D₄₃) decreased from 118.94 to 55.08 μm. Dynamic rheological measurements showed that the storage (G′) and loss (G′′) moduli of SPI gelled in the presence of okara were mostly higher than those of SPI gels alone and were increased as the okara amounts increased. Linear law analysis revealed that SPI–okara gels were weak gels and frequency independent. Fourier transform infrared spectroscopy showed that okara and transglutaminase influenced the prevalence of α‐helices, β‐turns, β‐sheet and random coils.     

The rheological property,antimicrobial stability and release evaluation of soya protein isolate/alginate‐based films incorporated with thymol

Soya protein isolate (SPI)/alginate (ALG)/montmorillonite (MMT)/thymol (THY) nanocomposite films were prepared with a codrying process to enhance the antimicrobial stability. The results showed higher gelation point temperature and more stable gelling network were obtained by the addition of MMT. Better thermal stability and sustained release effect was found in the coblended film containing MMT, in which THY release rate at 25 °C decreased with increasing MMT concentration but increased with temperature at a constant relative humidity. The SPI/ALG/THY, SPI/ALG/THY‐CO and SPI/ALG/THY‐CO‐0.6 (MMT content = 0.6 g g^?1 SPI) films effectively inhibited the growth of Escherichia coli by 0.95, 0.91 and 0.70 log cfu mL^?1 and of Staphylococcus aureus by 0.94, 0.89 and 0.73 log cfu mL^?1, respectively, on the surface of raw sausage, compared to the control film.     

Optimisation of soya bean oil bleaching by ultrasonic processing and investigate the physico‐chemical properties of bleached soya bean oil

In this study, an ultrasonic bleaching method for soya bean oil under different conditions was optimised by monitoring the reduction of oil‐containing colourants. Ultrasonic power, clay content, temperature and time had a significant interaction effect on (P < 0.05) the reduction of oil pigments and colourants. Under optimised conditions, red and yellow colour indices in the ultrasound‐bleached soya bean oil reduced to 74.44% and 75.55%, and 54.18% and 58.85%, respectively, at amplitudes of 85% and 65%. Carotenoid and chlorophyll concentrations also reduced to 81.19% and 83.62%, and 94.66% and 95.26%, respectively, at 85% and 65% ultrasonic power. The overall contents of sterols and tocopherols decreased using ultrasonic bleaching process compared with the neutralised soya bean oil. Although the peroxide value (PV) of the soya bean oil after ultrasonic and control bleaching reduced, this index was higher in the ultrasonic bleached oil than the control one. The results showed that the ultrasonic bleaching process could be an alternative to the industrial bleaching method as it reduced clay usage, temperature and time of bleaching about 35%, 35% and 10%, respectively.     

具有金属螯合活性的蚕豆蛋白酶解物的制备

目的探究蚕豆蛋白酶解物的金属螯合活性,研究其金属螯合活性与其抗氧化活性的关系。方法分别采用碱性蛋白酶、中性蛋白酶、木瓜蛋白酶对蚕豆蛋白进行酶解,并测定其水解物的抗氧化活性与金属螯合活性,选用碱性蛋白酶为酶解蚕豆蛋白制取金属螯合肽的最适酶,以酶解产物的水解度、抗氧化活性及金属螯合活性为测定指标获得合适的水解条件。结果 3种蛋白酶的蚕豆蛋白酶解产物都有金属螯合活性和抗氧化活性,碱性蛋白酶为酶解蚕豆蛋白的最适酶,最适酶解时间为4 h时,得到的酶解产物金属离子螯合率为88.22%,抑制羟自由基能力为220.70 U/mg,总还原力为0.03 U/mg。结论蚕豆蛋白酶解物具有一定的金属离子螯合活性与抗氧化活性,水解度对蚕豆蛋白酶解物的金属离子螯合活性及抗氧化活性有明显的影响,蚕豆蛋白酶解物的金属螯合活性与总还原力及抑制羟自由基能力呈现显著的正相关性,相关系数分别为0.925、0.968(P0.01)。     

In vitro digestibility of processed and fermented soya bean,cowpea and maize

Tropical legumes, ie soya bean and cowpea, were pre‐treated and subsequently fermented using pure cultures of Rhizopus spp. Impact of soaking, cooking and fermentation of the legumes on their digestibility was determined using an in vitro digestion method. Processing of white maize included, amongst others, natural lactic acid fermentation, cooking and saccharification using barley malt. An in vitro method was standardised to carry out comparative determinations of the dry matter digestibility of cereal and legume food samples as a function of processing conditions, without attempting to exactly mimic gastrointestinal digestion. Using this method based on upper digestive tract digestion, it was observed that digestibility of the legumes increased during cooking and fermentation. Cooking improved the total digestibility of both soya bean and cowpea from 36.5 to 44.8% and from 15.4 to 40.9% respectively. Subsequent fungal fermentation increased total digestibility only by about 3% for both soya bean and cowpea. Digestibility was also influenced by fungal strain and fermentation time. Cooking and subsequent saccharification using malt almost tripled total digestibility of white maize from 25.5 to 63.6%, whereas lactic fermentation of maize had no effect on in vitro dry matter digestibility. Although total digestibility of cooked legumes was only slightly improved by mould fermentation (3% for both soya bean and cowpea), the level of water‐soluble dry matter of food samples increased during fermentation with Rhizopus oryzae from 7.0 up to 27.3% for soya bean and from 4.3 up to 24.1% for cowpea. These fermented products could therefore play a role as sources of easily available nutrients for individuals suffering from digestive disorders. © 2000 Society of Chemical Industry     

Extraction and physicochemical properties of soya bean protein and oil by a new reverse micelle system compared with other extraction methods

Reverse micelle extraction is a novel technology for the separation of plant components such as proteins and oil. In this study, sodium bis(2‐ethylhexyl) sulphosuccinate (AOT) reverse micelle system and AOT/Tween 85 reverse micelle system were used to extract soya bean protein and oil from soya bean flour. The physicochemical properties of the protein and oil extracted were investigated and compared with traditional extraction methods. The results showed that the efficiency of forward extraction of soya bean protein using an AOT/Tween 85 reverse micelle system was superior to that using an AOT reverse micelle system at the optimal extraction conditions. In addition, soya bean proteins extracted using reverse micelle extraction had no unordered structure under Fourier transform infrared spectroscopy. The acid and peroxide values of oil products from two reverse micelle extractions were lower than that from immersion. The results indicated that AOT/Tween 85 reverse micelle system is effective in extracting soya bean protein and oil.     

Molecular structure characteristics,functional parameters and in vitro protein digestion of pressure‐cooked soya bean flours with different amounts of water

When a food product is cooked at high temperature with different proportions of water, the differential degradation that occurs in the molecular structure promotes changes in their functional characteristics. In this study, water and soya bean flour (dry base) were mixed in different ratios (3:1, 2:1, 1:1, 0.25:1 and 0:1) and pressure cooked at 130 °C, 1.5 kg cm^?2 for 30 min, cooled down to 40 °C and air dried for 24 h. Protein changes due to thermal process were determined with the ATR‐FTIR, as well as some functional parameters and in vitro protein digestibility. At higher water:soya bean flour ratios (3:1 and 2:1), the protein digestibility increased due to denaturation of tertiary structures, while urease activity (UA) and the functional characteristics of water absorption index (WAI) and water solubility index (WSI) decreased. Pearson's correlation analysis revealed that molecular changes on amide I, II and in α‐helix: β‐sheet ratios were directly related with the amount of added water.     

Formation of lysinoalanine following alkaline processing of soya bean meal in relation to the degradability of protein in the rumen

Effects of sodium hydroxide (NaOH) treatment on the formation of lysinoalanine (LAL) and on in-situ and in-vivo utilisation of soya bean meal (SBM) protein were investigated. Defatted SBM was sprayed with 0 (water), 25, 50 and 100 g NaOH (kg^?1 dry matter), dried at 80°C for 2 h and then fed to four rumen cannulated goats in a 4 × 4 Latin square as a mixed diet (9: 1 w/w) of sudangrass hay and the SBM. LAL was not detected in non-alkaline SBM, but the cross-linked amino acid increased according to the level of NaOH addition. The maximum concentration of LAL was 1.26 g per 16 g nitrogen when the highest level of NaOH was applied. The NaOH treatment did not alter the digestibility or the retention of nitrogen of the mixed diet. Addition of NaOH at 25 and 50 g (kg^?1 dry matter) lowered the solubility of protein, while the highest level of treatment had little effect. Lag time and rate of degradation of protein decreased due to the increasing level in NaOH treatment. A significant correlation (r = —0.860, P < 0.01) between LAL content and rate of protein degradation suggested that the formation of cross-linked amino acid would render protein more resistant to microbial degradation in the rumen.     

Modulation of the nutritional value of lupine wholemeal and protein isolates using submerged and solid‐state fermentation with Pediococcus pentosaceus strains

The influence of different factors (submerged and/or solid‐state fermentation, pediococci strain, lupine variety and protein isolation process) on the protein digestibility, total phenolic compounds (TPC) content and radical scavenging activity of Lupinus luteus and angustifolius wholemeal and protein isolates was evaluated. As safety factor, biogenic amines (Bas) formation was analysed. The Pediococcus pentosaceus strains No. 8, No. 9 and No. 10 are suitable starters for lupine wholemeal fermentation and both applied processes (fermentation and protein isolation) increase protein digestibility (by 10%). Higher TPC content in fermented wholemeal can be obtained, compare to isolates. In SMF isolates by 58.3%, 68.2%, 95.6%, 76.6%, lower content of phenylethylamine, putrescine, cadaverine and histamine, respectively was found. The highest protein digestibility and the lowest BAs content using submerged fermentation with pediococcus No. 8 in lupine variety Vilnius protein isolates can be obtained and this technology for high‐quality lupine proteins preparation can be recommended.     

Physicochemical properties and storage stability of spray‐dried soya bean sprout extract

Amylase is a very important enzyme due to its wide food applications. To preserve amylase activity in soya bean sprout extract (SSE), SSEs were spray‐dried with 10% maltodextrin and 0–3% alginic acids, and their physicochemical properties and storage stability were compared with freeze‐dried one. SSE exhibited maximum amylase activity at pH 7.0 and 60 °C, with the most active substrate specificity towards soluble starch. Spray‐dried SSEs exhibited higher water solubility index (WSI) and in vitro relative amylase activity but lower water vapour sorption (WVS) and smaller particle size than freeze‐dried SSE. For spray‐dried SSEs, particle size, WSI and in vitro relative amylase activity increased while WVS decreased with increasing % alginic acid. This study demonstrated that spray drying of SSE, especially with 10% maltodextrin and 2% alginic acid, was effective in keeping amylase active and stable during 7‐week storage at room temperature (25 °C).     

Preparation of fibrous textured protein from field bean globulins by wet non-spinneret spinning

General regularity of preparation of fibrous textured protein from field bean globulin fraction by wet non-spinneret spinning and the water absorption capacity of the textured protein were investigated. The optimal conditions for this process for minimum protein loss in the coagulation bath were determined. Use of a highly concentrated neutral protein solution (>500 g litre^?1) as a dope avoids the need for neutralisation and washing of the textured product. The textured protein obtained had a microfibrous structure.     

绿豆萌发过程中绿豆蛋白的功能特性及其抗氧化性

本文以绿豆为材料,研究了其萌发过程中绿豆蛋白的功能特性(溶解性、持水性、持油性、乳化性、起泡性、乳化稳定性、起泡稳定性)及抗氧化性(DPPH自由基清除率、金属离子螯合率、超氧阴离子自由基清除率)的动态变化。结果表明,随着萌发时间的不断延长,绿豆蛋白的溶解性、持水性、持油性、乳化性、起泡性均呈现先增加后降低的趋势,乳化稳定性和起泡稳定性得以增强。其中,溶解性萌发24 h时达到最高,萌发96 h最低;萌发的绿豆蛋白持水性、持油性和乳化性相对于未萌发的分别提高了1.57倍、4.13倍和2.47倍;乳化稳定性、起泡性和起泡稳定性较未萌发的分别提高了43.8%、46.6%和61.3%。此外,萌发过程中的绿豆蛋白抗氧化性呈现先升高后下降的趋势,萌发促进了绿豆蛋白的抗氧化性。其中,DPPH自由基清除率和金属离子螯合率均在绿豆萌发36 h达到最大,较未萌发的分别提高了73.8%和31.0%;超氧阴离子自由基清除率萌发48 h达到最大,较未萌发的提高了81.7%。随着绿豆萌发时间的延长,绿豆蛋白的功能特性和抗氧化性呈现先升高后下降的趋势,萌发中期(24~48 h)达到最大。因此,萌发提升了绿豆蛋白的功能特性和抗氧化性,扩大了其在食品加工中的应用,提高了其利用价值。