Galacto-oligosaccharides (GOS) have interest in the food industry due to their recognized functional properties. In this work, we studied the effect of a commercial βgalactosidase enzyme from Kluyveromyces lactis (YNL-2, GODO) and Lactobacillus acidophilus La-5, on GOS formation during the manufacture and storage of drinkable and stirred yogurts. In a preliminary step, GOS synthesis and lactose hydrolysis by βgalactosidase was evaluated at different initial lactose concentrations and doses of enzyme. The GOS formation was favored with increasing of lactose concentration and enzyme doses, while the hydrolysis dominated at lower level of lactose. In turn, the presence of GOS was already evident at 45 min of fermentation in yogurts with addition of βgalactosidase. Mean concentrations were 0.36 and 0.62 g/100 g for fresh drinkable and stirred yogurts, respectively. No changes in the GOS levels were observed through storage, indicating that they were stable in the products. The probiotic bacteria added were not able to produce GOS. The diminution of lactose was significant in yogurts with β-galactosidase;
The aim of this study was to propose and validate a new minicurd model of young hard cheese. Curd particles and whey obtained from conventional cheese making of Reggianito Argentino were separated and frozen. Then, both fractions were thawed and the mixture of whey and curds was reconstituted, from which minicurds were made on the laboratory scale. Repeatability and the effect of freezing on minicurd composition were investigated by assessing pH, protein and moisture contents, sodium chloride content, and total thermophilic lactic flora counts. Good repeatability was achieved, and no significant differences were found between minicurds made from fresh compared with frozen materials. Composition of the minicurd was appropriate for modeling Reggianito Argentino cheese.
RESUMEN Detección de adulteraciones en grasa láctea a través del tratamiento por regresión lineal múltiple de perfiles de ácidos grasos totales.Se determinó el perfil de ácidos grasos totales de muestras de grasa láctea genuina de una importante cuenca lechera de la República Argentina obtenidas durante un año (2002)(2003), y de aceites de girasol, soja, coco y sebos vacuno y porcino, con el objetivo de estudiar el perfil característico de la grasa láctea y poder detectar adulteraciones de la misma con las grasas mencionadas.Se empleó el método de transesterificación de los triglicéridos en medio ácido, utilizando etanol-ácido sulfúrico, y se cuantificaron los ésteres etílicos por cromatografía de gases empleando dos estándares internos que se adicionaron a la grasa anhidra (C7:0 y C17:0). Se cuantificaron los ácidos grasos más característi-cos de las grasas estudiadas.Se obtuvieron matemáticamente los perfiles de mezclas de las grasas lácteas con las distintas materias grasas mencionadas, cubriendo un rango del 2 al 10% de adición (porcentaje de adulteración) para los aceites y grasas vegetales y hasta el 15% para las grasas de origen animal. De esta manera se obtuvieron diferentes matrices de datos a las que se les aplicó el método de regresión lineal múltiple con selección por stepwise con el propósito de obtener una función que relacionara el porcentaje de adulteración con los perfiles de ácidos grasos totales para cada materia grasa ensayada como adulterante.Se obtuvieron buenos coeficientes de correlación para las matrices de datos analizadas. Las ecuaciones se validaron con el empleo del método de validación interna o cruzada, con muestras genuinas de grasa láctea y con mezclas preparadas por balances de masa de dichas grasas lácteas con las distintas materias grasas adulterantes. Las ecuaciones obtenidas mostraron un buen ajuste para la predicción de las adulteraciones estudiadas. PALABRAS-CLAVE: Ácidos grasos totales -Adulteración -Regresión lineal múltiple stepwise SUMMARY Detection of adulterations in milk fat by multiple regression analysis of total fatty acids profile.The total fatty acids profile of a genuine milk fat from an important milk producing area of Argentina was determined together with the total fatty acids profiles of sunflower, soybean and coconut oils and bovine and porcine fats. These results were used for characterization of the fatty acid profile of genuine milk fat and for detection of the adulteration of milk fat with those oils and fats.Triglycerides were transesterified in an acid medium with ethanol -sulfuric acid. Ethyl esters were quantified by gas chromatography using two internal standards (C7:0 a n d C17:0) added to the anhydrous fat. The most characteristic fatty acids were determined.The fatty acids profiles of mixtures of milk fat with vegetable and animal fats were mathematically calculated. Vegetable oils were added from 2 to 10%, while animal fats were added up to 15%. In this way different data matrices were obtained. Stepwise multiple regression analysis was appli...
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