Modeling lactose hydrolysis for efficiency and selectivity: Toward the preservation of sialyloligosaccharides in bovine colostrum whey permeate.

Enzymatic hydrolysis of lactose has been shown to improve the efficiency and selectivity of membrane-based separations toward the recovery of bioactive oligosaccharides. Achieving maximum lactose hydrolysis requires intrinsic process optimization for each specific substrate, but the effects of those processing conditions on the target oligosaccharides are not well understood. Response surface methodology was used to investigate the effects of pH (3.25-8.25), temperature (35-55°C), reaction time (6 to 58 min), and amount of enzyme (0.05-0.25%) on the efficiency of lactose hydrolysis by ß-galactosidase and on the preservation of biologically important sialyloligosaccharides (3'-siallylactose, 6'-siallylactose, and 6'-sialyl-N-acetyllactosamine) naturally present in bovine colostrum whey permeate. A central composite rotatable design was used. In general, ß-galactosidase activity was favored at pH values ranging from 3.25 to 5.75, with other operational parameters having a less pronounced effect. A pH of 4.5 allowed for the use of a shorter reaction time (19 min), lower temperature (40°C), and reduced amount of enzyme (0.1%), but complete hydrolysis at a higher pH (5.75) required greater values for these operational parameters. The total amount of sialyloligosaccharides was not significantly altered by the reaction parameters evaluated, suggesting specificity of ß-galactosidase from Aspergillus oryzae toward lactose as well as the stability of the oligosaccharides at pH, temperature, and reaction time evaluated.

Effect of pH and interaction between egg white protein and hydroxypropymethylcellulose in bulk aqueous medium on foaming properties.

Egg white protein (EW) is used as surface-active ingredient in aerated food and hydroxypropylmethylcellulose (HPMC) is a polysaccharide that behaves as a surfactant. This study aimed at investigating the effects of process parameters biopolymer concentration (2.0-5.0%, w/w), EW:HPMC ratio (2:1-18:1), pH (3.0-6.0), and the influence of biopolymers' behavior in aqueous solution at different pH on the foaming properties (overrun, drainage, and bubble growth rate). Process parameters had effect on foaming properties. The pH was the major factor influencing the type of EW/HPMC interaction and affected the foaming properties of biopolymer mixture. At pH 3.0, EW and HPMC showed thermodynamic compatibility leading to better foaming properties, higher foaming capacity, and stability than without HPMC addition whereas at pH 4.5 and 6.0, EW and HPMC are incompatible that causes lower stability concerning the disproportionation comparing to foam without HPMC. At pH between 3.0 and 4.5, HPMC improves foaming properties of aerated products.

Influence of protein-pectin electrostatic interaction on the foam stability mechanism.

This study aimed at evaluating the effect of three independent variables: biopolymer concentration (egg white proteins and pectin) (2.0-4.0%, w/w); protein:pectin ratio (15:1-55:1); and temperature (70-80 °C), at pH 3.0, using a central composite design on the foaming properties (overrun, drainage and bubble growth rate). Foams produced with protein:pectin ratio 15:1 showed the lowest bubble growth rate and the greatest drainage, whereas protein:pectin ratio 55:1 presented the lowest drainage. Complexes obtained with protein:pectin ratio 15:1 were close to electroneutrality and showed larger size (95.91 ± 8.19 µm) than those obtained with protein:pectin ratio 55:1 (45.92 ± 3.47 µm) not electrically neutral. Larger particles seemed to build an interfacial viscoelastic network at the air-water interface with reduced gas permeability, leading to greater stability concerning the disproportionation. Soluble complexes of smaller sizes increased viscosity leading to a low drainage of liquid and inhibiting the bubbles coalescence.

Effect of the simultaneous interaction among ascorbic acid, iron and pH on the oxidative stability of oil-in-water emulsions.

The objective of this study was to demonstrate how different factors can simultaneously influence the oxidative stability of an oil-in-water emulsion, and how these factors can be used to enlarge the variation range of oxidation markers, expressed as peroxide value (PV) and TBARS. Initially, a Plackett-Burman design was used to screen seven factors (temperature, pH, and iron, copper, ascorbyl palmitate, ascorbic acid, and sodium chloride concentrations). A temperature elevation of 30 to 60 °C reduced PV and TBARS, a pH change from 3.0 to 7.0 increased PV and reduced TBARS, and the presence of ascorbic acid (1 mmol/L) had no significant effect on PV but increased TBARS (p < 0.05). Thus, the temperature was fixed at 30 °C, and an emulsion was formulated with different combinations of ascorbic acid, iron, and pH according to a central composite rotatable design. Regression models were fitted to PV and TBARs responses and optimized to get the higher values of both markers of oxidation. The optimized emulsion contained 1.70 mmol/L AH (ascorbic acid) and 0.885 mmol/L FeSO(4) · 7H(2)O (1.0 mmol/L Fe(2+)) at pH 5.51 and 30 °C. The range of variation observed for oxidation markers in the optimized emulsion model (PV, 0-4.27 mequiv/L; TBARS, 0-13.55 mmol/L) was larger than the variation observed in the nonoptimized model (PV, 0-1.05 mequiv/L; TBARS, 0-1.00 mmol/L). The antioxidant activity of six compounds (Trolox, α-tocopherol, caffeic acid, gallic acid, catechin, and TBHQ) was evaluated using the optimized emulsion conditions. After application of the Tukey HSD post hoc statistical test, the samples that were not different (p < 0.05) in the nonoptimized emulsions showed a significant difference in the optimized emulsions. Considering the importance of the interactions on oxidation studies, our model represents a significant improvement in a direct methodology that can be applied to evaluate natural compounds under different combination of factors.

Otimização e validação de metodologia analitica para determinação de flavonóis e flavonas por CLAE em hortaliças / Optimization and validation of HPLC methodology for determining flavonols and flavones in vegetables

O objetivo deste trabalho foi otimizar a metodologia analítica para determinação de flavonóis e flavonas em hortaliças. A hidrólise foi otimizada utilizando-se Delineamento Composto Central Rotacional (DCCR)para investigar os efeitos da concentração de HCl e do tempo de hidrólise. Essa etapa foi realizada simultaneamente com a extração por metanol aquoso 50%, em refluxo a 90ºC. Foi utilizado cromatógrafo líquido Waters com coluna Nova-Pak C18 e detector de arranjo de diodos. Os compostos estudados foram miricetina (M), quercetina (Q), kaempferol (K), luteolina (L) e apigenina (A). As condições ótimas encontradas para hidrólise de cada hortaliça foram: 1,0M HCl/6 horas para espinafre e couve, 1,6M HCl/5 horas para rúcula, 1,2M HCl/2 horas para alface, 1,7M HCl/4,3 horas para salsa e 0,8M HCl/2,5 horas para cebola. O melhor gradiente para separação (CLAE) dos flavonóides das hortaliças em estudo foi constituído de metanol:água (acidificados com 0,3% de ácido fórmico) 20:80, chegando a 45:55 em 5 minutos, 48:52 em 17 minutos e voltando a 20:80 em 20 minutos. As curvas analíticas apresentaram coeficientes de correlação maiores que 0,99. Os limites de detecção foram de 0,5, 0,4, 0,5, 0,6 e 1,0μg/mL, respectivamente, para M, Q, L, K e A.

The objective of this investigation was to optimize the analytical methodology for determining flavonols and flavones in vegetables. The hydrolysis procedure was optimized using Central Composite Rotational Design (CCRD) to investigate the effects of HCl concentration and hydrolysis time. This step was carried out simultaneously with extraction with 50% aqueous methanol, and refluxing at 90°C. A Waters liquid chromatograph, with Nova-Pak C18 column and photodiode array detector, was used. The analyzed compounds were myricetin (M), quercetin (Q), kaempferol (K), luteolin (L), and apigenin (A). The optimum conditions found for hydrolysis for each vegetable were: 1.0M HCl for 6 hours for spinach and kale, 1.6M HCl for 5 hours for roquette, 1.2M HCl for 2 hours for lettuce, 1.7M HCl for 4.3 hours for parsley, and 0.8M HCL for 2.5 hours for onion. The best gradient (HPLC) for separating flavonoids from these vegetables consisted of methanol:water (acidified with 0.03% formic acid) 20:80, changing to 45:55 in 5 minutes, 48:52 in 17 minutes, returning to 20:80 in 20 minutes. The standard curves of the flavonoids had coefficients of correlation higher than 0.99. The detection limits were 0.5, 0.4, 0.5, 0.6 and 1.0μg/mL for M, Q, L, K, and A, respectively.