RESUMEN
Biopolymers such as tragacanth, an anionic polysaccharide gum, can be alternative polymeric carrier for physiologically important peptides and proteins. Characterization of tragacanth is thus essential for providing a foundation for possible applications. Rheological studies colloidal solution of tragacanth at pH 3, 5 or 7 were carried out by means of steady shear and small amplitude oscillatory measurements. Tragacanth mucoadhesivity was also analyzed using an applicable rheological method and compared to chitosan, alginate and PVP. The particle size and zeta potential were measured by a zetasizer. Thermal properties of solutions were obtained using a differential scanning calorimetry. The solution exhibited shear-thinning characteristics. The value of the storage modulus (G') and the loss modulus (Gâ³) increased with an increase in angular frequency (Ω). In all cases, loss modulus values were higher than storage values (Gâ³>G') and viscous character was, therefore, dominant. Tragacanth and alginate showed a good mucoadhesion. Tragacanth upon dispersion created particles of a submicron size with a negative zeta potential (-7.98 to -11.92 mV). These properties were pH dependant resulting in acid gel formation at pH 3.5. Tragacanth has thus a potential to be used as an excipient for peptide/protein delivery.
Asunto(s)
Portadores de Fármacos/química , Mucinas Gástricas/química , Insulina/química , Tragacanto/química , Adhesivos , Administración Oral , Alginatos/química , Animales , Rastreo Diferencial de Calorimetría , Quitosano/química , Elasticidad , Hidrogeles , Concentración de Iones de Hidrógeno , Tamaño de la Partícula , Povidona/química , Reología , Espectroscopía Infrarroja por Transformada de Fourier , Porcinos , ViscosidadRESUMEN
Processing conditions during ultrafiltration of skim milk influence properties of the casein micelle and thereby the physical properties of milk protein concentrate (MPC). The aim of the study was to establish the effects of pH adjustment of skim milk feed to obtain MPC with desired emulsification properties. The ultrafiltration was conducted using commercially pasteurized skim milk with the pH adjusted to 6.7 (control), 6.3, 5.9, or 5.5 at 15°C until a volume concentration factor of 5 was reached. Effects of pH adjustment on selected physico-chemical properties (Ca content, particle size, ζ-potential) and functionalities (solubility, heat stability, emulsification capacity, and stability) of MPC were determined. Lowering the feed pH solubilized colloidal calcium phosphate that substantially contributed to modifying the properties of casein. This caused a reduction in the particle size while increasing the net negative charge. The structural modifications in proteins were manifested in the Fourier transform infrared spectra. Subsequent concentration did not induce any further protein structural changes. Such modifications to the casein micelles and colloidal calcium phosphate negatively affected the solubility and heat stability of the corresponding MPC powders. However, the emulsion activity index improved only until the pH of the feed was lowered to 5.9 and declined when pH was dropped to 5.5, followed with the loss of stability. Readjusting the pH of MPC powder dispersions to 6.7 restored their surface properties and thereby their functionality. Lowering the feed pH also negatively affected the membrane performance by clogging the membrane pores and lowering the flux, particularly at pH 5.5. Adjusting pH to 5.9 produced MPC with optimum emulsifying properties with minimal influence on membrane performance.
Asunto(s)
Manipulación de Alimentos , Membranas Artificiales , Proteínas de la Leche/análisis , Leche/química , Ultrafiltración/instrumentación , Animales , Caseínas/análisis , Concentración de Iones de Hidrógeno , Micelas , Tamaño de la Partícula , Pasteurización , Polvos/análisis , Solubilidad , Ultrafiltración/métodosRESUMEN
The aim of this study was to examine the influence of using exopolysaccharide (EPS) producing strain of Streptococcus thermophilus on the viability of yogurt starters, their proteolytic and angiotensin-I converting enzyme-inhibitory activities, and on the textural and rheological properties of the low-fat yogurt during storage at 4 degrees C for 28 d. The use of an EPS-producing strain of S. thermophilus did not have influence on pH, lactic acid content, or the angiotensin-I converting enzyme-inhibition activity of low-fat yogurt. However, EPS showed a protective effect on the survival of Lactobacillus delbrueckii ssp. bulgaricus. Presence of EPS reduced the firmness, spontaneous whey separation, yield stress, and hysteresis loop area but not the consistency and flow behavior index of low-fat yogurt.
Asunto(s)
Manipulación de Alimentos , Péptido Hidrolasas/metabolismo , Polisacáridos Bacterianos/metabolismo , Refrigeración , Sensación , Streptococcus thermophilus/enzimología , Yogur/normas , Inhibidores Enzimáticos/metabolismo , Grasas , Concentración de Iones de Hidrógeno , Ácido Láctico/análisis , Lactobacillus delbrueckii/fisiología , Peptidil-Dipeptidasa A/metabolismo , Polisacáridos Bacterianos/análisis , Reología , Streptococcus thermophilus/fisiología , Yogur/análisis , Yogur/microbiologíaRESUMEN
The objective of this study was to examine the effect of Versagel on the growth and proteolytic activity of Streptococcus thermophilus 1275 and Lactobacillus delbrueckii ssp. bulgaricus 1368 and angiotensin-I converting enzyme inhibitory activity of the peptides generated thereby as well as on the physical properties of low-fat yogurt during a storage period of 28 d at 4 degrees C. Three different types of low-fat yogurts, YV0, YV1, and YV2, were prepared using Versagel as a fat replacer. The fermentation time of the low-fat yogurts containing Versagel was less than that of the control yogurt (YV0). The starter cultures maintained their viability (8.68 to 8.81 log CFU/g of S. thermophilus and 8.51 to 8.81 log CFU/g of L. delbrueckii ssp. bulgaricus) in all the yogurts throughout the storage period. There was some decrease in the pH of the yogurts during storage and an increase in the concentration of lactic acid. However, the proteolytic and ACE-inhibitory potential of the starter cultures was suppressed in the presence of Versagel. On the other hand, the addition of Versagel had a positive impact on the physical properties of the low-fat yogurt, namely, spontaneous whey separation, firmness, and pseudoplastic properties.
Asunto(s)
Sustitutos de Grasa/química , Microbiología de Alimentos , Yogur/análisis , Ácido Acético/análisis , Inhibidores de la Enzima Convertidora de Angiotensina/química , Recuento de Colonia Microbiana , Fermentación , Manipulación de Alimentos , Concentración de Iones de Hidrógeno , Ácido Láctico/análisis , Lactobacillus delbrueckii/crecimiento & desarrollo , Proteínas de la Leche/análisis , Reología , Streptococcus thermophilus/crecimiento & desarrollo , Yogur/microbiologíaRESUMEN
This study investigated the influence of incorporating Raftiline HP on the pH, growth, proteolytic, and angiotensin-I converting enzyme inhibitory activities and on spontaneous whey separation, firmness, and rheological properties of low-fat yogurts during storage for 28 d at 4 degrees C. Three types of yogurts were prepared from skim milk containing 0% (YI0, control), 2% (YI2), and 3% (YI3) Raftiline HP, respectively. The incorporation of Raftiline HP improved the growth of starter organisms, particularly that of Lactobacillus delbrueckii ssp. bulgaricus, resulting in shorter fermentation time. There was a significant improvement in total proteolysis, which was highest in yogurt containing 3% Raftiline HP. The ACE inhibitory activity was maximal in YI3 compared to YI2 and YI0. Incorporation of Raftiline HP did not affect whey separation and firmness of the low-fat yogurts. All these products were more fluid like with distinct pseudoplastic properties and lesser ability to resist deformation upon applied shear.
Asunto(s)
Inhibidores de la Enzima Convertidora de Angiotensina/metabolismo , Sustitutos de Grasa/química , Microbiología de Alimentos , Lactobacillus delbrueckii/crecimiento & desarrollo , Streptococcus thermophilus/crecimiento & desarrollo , Yogur/análisis , Ácido Acético/análisis , Recuento de Colonia Microbiana , Fermentación , Concentración de Iones de Hidrógeno , Inulina/química , Ácido Láctico/análisis , Lactobacillus delbrueckii/metabolismo , Proteínas de la Leche/análisis , Reología , Streptococcus thermophilus/metabolismo , Yogur/microbiologíaRESUMEN
This study was conducted to examine the growth, proteolytic profiles as well as angiotensin-I converting enzyme (ACE) and alpha-glucosidase (alpha-glu) inhibitory potentials of selected strains of lactic acid bacteria (LAB). Two strains each of yogurt bacteria (Streptococcus thermophilus-1275 and 285, and Lactobacillus delbrueckii ssp. bulgaricus-1092 and 1368), and probiotics (L. acidophilus-4461 and 33200, and L. casei-2607 and 15286, and 1 strain of Bifidobacterium longum 5022), were cultivated in reconstituted skim milk (RSM) at 37 degrees C and their proteolytic profiles and ACE as well as alpha-glu inhibitory activities were determined. Among all the strains of lactic acid bacteria studied, yogurt bacteria grew very well, with the exception of L. delbrueckii ssp. bulgaricus 1368 which showed a slower growth during the initial 3 h of incubation. The growth pattern corresponded well with the decrease in pH for the organisms. All the organisms showed an increase in proteolysis with time. The variations in proteolytic capabilities translated into corresponding variations in ACE inhibitory potential of these organisms. Bifidobacterium longum 5022 showed the highest ACE inhibitory potential followed by L. delbrueckii ssp. bulgaricus 1368, L. casei 15286, S. thermophilus 1275, and L. acidophilus 4461. Organisms with high intracellular enzymatic activities grew well. Also, aminopeptidases of strains of L. acidophilus 4461 and S. thermophilus 1275 that could better utilize proline containing substrates showed enhanced ACE inhibitory potential. Lactic acid bacteria possessed the ability to inhibit alpha-glu activity, which endowed them an antidiabetic property as well.
Asunto(s)
Inhibidores de la Enzima Convertidora de Angiotensina/metabolismo , Inhibidores de Glicósido Hidrolasas , Lactobacillus/crecimiento & desarrollo , Lactobacillus/metabolismo , Leche/química , Leche/microbiología , Animales , Bifidobacterium/enzimología , Bifidobacterium/crecimiento & desarrollo , Bifidobacterium/metabolismo , Fermentación , Microbiología de Alimentos , Humanos , Lactobacillus/enzimología , Lactobacillus acidophilus/enzimología , Lactobacillus acidophilus/crecimiento & desarrollo , Lactobacillus acidophilus/metabolismo , Lacticaseibacillus casei/enzimología , Lacticaseibacillus casei/crecimiento & desarrollo , Lacticaseibacillus casei/metabolismo , Lactobacillus delbrueckii/enzimología , Lactobacillus delbrueckii/crecimiento & desarrollo , Lactobacillus delbrueckii/metabolismo , Probióticos , Streptococcus thermophilus/enzimología , Streptococcus thermophilus/crecimiento & desarrollo , Streptococcus thermophilus/metabolismo , Yogur/microbiología , alfa-Glucosidasas/metabolismoRESUMEN
In this study, the influence of a protein-based fat replacer, Versagel added at 1% and 2% (w/v) to reconstituted skim milk (RSM), on the growth and metabolic activities of selected strains of yogurt starters (Streptococcus thermophilus and Lactobacillus delbrueckii ssp. bulgaricus) as well as probiotic organisms (Lactobacillus casei, Lactobacillus acidophilus, and Bifidobacterium longum) was examined. Addition of Versagel resulted in significantly improved growth of S. thermophilus and B. longum but inhibited that of L. casei, L. acidophilus, and L. delbrueckii ssp. bulgaricus. This is also reflected in the extent of reduction of pH in RSM with added Versagel by these organisms. Among the biochemical activities, proteolytic activity of all the organisms except B. longum was adversely affected by the presence of Versagel, although the angiotensin-I converting enzyme (ACE) inhibitory and alpha-glucosidase (alpha-glu) inhibitory activities were improved. Versagel at 1% level influenced the growth, while ACE inhibitory and alpha-glu inhibitory activities of the organisms were better at 2% level.