Impact of environmental stresses on the stability of acidic oil-in-water emulsions prepared with tofu whey concentrates.

The emulsifying properties of tofu-whey concentrates (TWCs) at pH 3.0, 4.0, and 5.0, and the stability of the resultant oil-in-water emulsions against freeze-thawing (24 h, -20 °C) and controlled or mechanical stress (orbital stirring at 275 rpm, 40 min) were addressed. TWCs were prepared from tofu-whey by heating at 50 °C (8.0 kPa) or 80 °C (24.0 kPa), dialysis (4 °C, 48 h), and freeze-drying, giving the samples TWC50 and TWC80, respectively. The particle size and interfacial properties at the oil/water interface were measured. Emulsions were prepared by mixing the TWC aqueous dispersions (1.0% protein w/w) and refined sunflower oil (25.0% w/w) by high-speed and ultrasound homogenization. The preparation of TWCs at higher temperatures (80 °C) promoted the formation of species of larger particle size, a slight decrease of interfacial activity, and the adsorption of more rigid biopolymer structures associated with an increase of film viscoelasticity in interfacial rheology measurements. The emulsifying properties of both concentrates were enhanced with decreasing pH (5.0-3.0), through a significant decrease of particle size (D4,3) and flocculation degree (FD), but only those prepared with TWC80 exhibited higher stability to freeze-thawing and mechanical stress at pH 3.0. This could be ascribed to a combination of low initial D4,3 and FD values, high protein load, and the presence of rigid species that impart high viscoelasticity to the oil/water interface. These results would be of great importance for the utilization of TWCs as food emulsifiers in acidic systems to impart high stability to environmental stresses.

Influence of chemical composition and structural properties on the surface behavior and foam properties of tofu-whey concentrates in acid medium.

This article focuses on the impact of chemical composition and structural properties of tofu-whey concentrates on their surface behavior at the air/water interface and foaming properties in acid medium. Liquid tofu-whey (pH 5.6 ±â€¯0.1) was concentrated at three combinations of temperature and pressure (50 °C-8.0 kPa, 65 °C-16.0 kPa and 80 °C-24.0 kPa), with further dialysis (4 °C, 48 h) and freeze-drying, giving the samples TWC50, TWC65 and TWC80, respectively. The increase of temperature during the concentration step promoted the enrichment of the concentrates in crude protein and calcium, without appreciable changes in the yield, the carbohydrate content and the polypeptide composition. For TWC80, the increase the degree of glycosylation and the intensity of the hydrophobic effect promoted the decrease of molecular flexibility and the formation of compact aggregates mediated by disulfide bridges as was evidenced by tricine-SDS-PAGE, TGA and FTIR assays. These structural differences have a pronounced impact of the pH-dependence of turbidity and solubility of protein and polysaccharides. At pH 4.0 all concentrates evidenced a ζ-potential close to zero, which enhanced their foam ability (overrun >1500%). Nevertheless, at this pH, TWC80 showed both the highest carbohydrate-to-protein mass ratio in the soluble fraction (>1.8) and foam stability (FS). Thus, the improvement of FS at pH 4.0 would be associated to the effective adsorption of compact rich-in-protein aggregates at the air/water interface and the higher content of soluble polysaccharides in the bulk phase. These findings are relevant for the application of tofu-whey concentrates in acidic dispersed systems, such as foams and aerated food emulsions.

Aflatoxins distribution in fractions derived from tofu production.

Tofu or bean curd is obtained from soybean seeds being a widespread food product in Asia. The commodity used for its production can be contaminated with aflatoxins, which are secondary metabolites synthetised by species of Aspergillus flavus and A. parasiticus. Intake of contaminated food products causes toxic effects on consumers. The aim of this work was to study aflatoxin distribution in fractions obtained from pilot-scale tofu production with contaminated soybeans. The presence of the aflatoxins B1, B2, G1 and G2 (AFs) in soaking water, okara, whey and tofu was analysed. Aflatoxin analysis was performed by HPLC with fluorescence detection. The distribution of aflatoxins in all the analysed fractions was not a normal distribution. The liquid fractions (soaking water and whey) had less contamination than solid fractions (tofu and okara). The percentage AFB1 remaining in nutritionally important fractions, okara and tofu, was between 6.2% and 67.7% (median = 18.1%) and 0.5% and 13.2% (median = 3.5%), respectively. AFB2, AFG1 and AFG2 had a similar distribution. These results showed that throughout tofu production, AFs can be present in the products intended for human consumption.

Brazilian soybean cultivars: tofu-making characteristics and acceptance by consuming market / Cultivares brasileiras de soja: características para a produção de tofu e aceitação pelo mercado consumidor

In this investigation, eight Brazilian soybean cultivars were evaluated with respect to their tofu-making potential and final products underwent sensory acceptance. Grains from each cultivar showed differences related to size, seedcoat content and water absorption capacity. All cultivars displayed similar tofu yield, but resultant products presented distinct hardness. Mean values obtained on attribute acceptance testing showed tofu were different in terms of flavor and texture but not in global evaluation. Internal Preference Mapping indicated consumer segmentation in three different groups. This information could guide tofu manufacturers in raw material selection, in order to define one or more soybean cultivars that better satisfy the expectations of the consumers.

Neste trabalho, oito cultivares de soja brasileira foram avaliadas quanto ao seu potencial para produção de tofu e os produtos finais do processamento foram submetidos à aceitação sensorial. Os grãos das cultivares apresentaram diferenças em termos de tamanho (11-22 g/100 grãos), conteúdo de cascas (6,3-8,3 g casca/100 g grãos) e capacidade de absorção de água (121-140 g água/100 g grãos). Todas as cultivares foram semelhantes no rendimento em tofu (média de 271 g tofu/100g grãos), mas os produtos resultantes apresentaram dureza distinta (2,3-3,8 N). As médias obtidas no teste de aceitação de atributos evidenciaram diferenças entre os tofus, em termos de sabor (notas entre 5,3 e 6,2) e textura (notas entre 5,6 e 6,4), mas não na aceitação global (média de 5,8). O Mapa de Preferência Interno mostrou uma segmentação dos consumidores em três grupos distintos. Esta informação pode nortear uma empresa fabricante de tofu na escolha da matéria-prima, definindo uma ou mais cultivares de soja que melhor atendam às expectativas dos consumidores.

Brazilian soybean cultivars: tofu-making characteristics and acceptance by consuming market / Cultivares brasileiras de soja: características para a produção de tofu e aceitação pelo mercado consumidor

In this investigation, eight Brazilian soybean cultivars were evaluated with respect to their tofu-making potential and final products underwent sensory acceptance. Grains from each cultivar showed differences related to size, seedcoat content and water absorption capacity. All cultivars displayed similar tofu yield, but resultant products presented distinct hardness. Mean values obtained on attribute acceptance testing showed tofu were different in terms of flavor and texture but not in global evaluation. Internal Preference Mapping indicated consumer segmentation in three different groups. This information could guide tofu manufacturers in raw material selection, in order to define one or more soybean cultivars that better satisfy the expectations of the consumers.

Neste trabalho, oito cultivares de soja brasileira foram avaliadas quanto ao seu potencial para produção de tofu e os produtos finais do processamento foram submetidos à aceitação sensorial. Os grãos das cultivares apresentaram diferenças em termos de tamanho (11-22 g/100 grãos), conteúdo de cascas (6,3-8,3 g casca/100 g grãos) e capacidade de absorção de água (121-140 g água/100 g grãos). Todas as cultivares foram semelhantes no rendimento em tofu (média de 271 g tofu/100g grãos), mas os produtos resultantes apresentaram dureza distinta (2,3-3,8 N). As médias obtidas no teste de aceitação de atributos evidenciaram diferenças entre os tofus, em termos de sabor (notas entre 5,3 e 6,2) e textura (notas entre 5,6 e 6,4), mas não na aceitação global (média de 5,8). O Mapa de Preferência Interno mostrou uma segmentação dos consumidores em três grupos distintos. Esta informação pode nortear uma empresa fabricante de tofu na escolha da matéria-prima, definindo uma ou mais cultivares de soja que melhor atendam às expectativas dos consumidores.