Suitability of buttermilk for fermentation with Lactobacillus helveticus and production of a functional peptide-enriched powder by spray-drying.

AIM: To ferment buttermilk, a low-cost by-product of the manufacture of butter, with a proteolytic strain of Lactobacillus helveticus, to enhance its value by the production of a functional peptide-enriched powder. METHODS AND RESULTS: Buttermilk was fermented with Lact. helveticus 209, a strain chosen for its high proteolytic activity. To enhance the release of peptidic fractions, during fermentation pH was kept at 6 by using NaOH, Ca(CO)(3) or Ca(OH)(2). Cell-free supernatant was recovered by centrifugation, supplemented or not with maltodextrin and spray-dried. The profile of peptidic fractions released was studied by RP-HPLC. The lactose, Na and Ca content was also determined. The powder obtained was administered to BALB/c mice for 5 or 7 consecutive days, resulting in the proliferation of IgA-producing cells in the small intestine mucosa of the animals. CONCLUSIONS: Buttermilk is a suitable substrate for the fermentation with Lact. helveticus 209 and the release of peptide fractions able to be spray-dried and to modulate the gut mucosa in vivo. SIGNIFICANCE AND IMPACT OF THE STUDY: A powder enriched with peptides released from buttermilk proteins, with potential applications as a functional food additive, was obtained by spray-drying. A novel use of buttermilk as substrate for lactic fermentation is reported.

Influence of milk-clotting enzyme concentration on the alphas1-casein hydrolysis during soft cheeses ripening.

We studied the influence of the dose of milk-clotting enzyme on alphas1-CN degradation, soluble nitrogen production, and sensory profile for an Argentinean soft cheese: Cremoso Argentino. Five different types of cheeses were produced: 1) control cheeses with normal technology, 2) cheeses with inactivated milk-clotting enzyme, 3) cheeses with inactivated milk-clotting enzyme, without starter (acidified with glucono delta lactone), 4) cheeses with a half dose of milk-clotting enzyme, and 5) cheeses with a double dose of milk-clotting enzyme. Proteolysis was assessed by isoelectric focusing electrophoresis of the insoluble fraction at pH 4.6, followed by densitometric quantification. Soluble nitrogen at pH 4.6, expressed as a percentage of total nitrogen and defined as ripening index was also performed. A sensorial panel evaluated the cheeses at the end of ripening. The hydrolysis level of alphas1-CN depended on the milk-clotting enzyme dose used in cheese making. Cheeses without active coagulant did not show degradation at the end of ripening, while cheeses with half and whole doses showed proportional degradations to coagulant dose. Cheese with a double dose of coagulant did not show higher alphas1-CN hydrolysis than normal cheese. No difference was found between cheeses with and without microbiological starter, indicating that the selected culture, composed of thermophilic strains, was unable to attack the whole casein. A high linear correlation was found between ripening index and the relation Sensorial characteristics of cheeses agree with objective analysis. Cheeses without active coagulant were hard and crumbly, while cheeses with normal dose were soft and creamy.

Global pollution of surface waters from point and nonpoint sources of nitrogen.

Global 0.5- by 0.5-degree resolution estimates are presented on the fate of nitrogen (N) stemming from point and nonpoint sources, including plant uptake, denitrification, leaching from the rooting zone, rapid flow through shallow groundwater, and slow flow through deep groundwater to riverine systems. Historical N inputs are used to describe the N flows in groundwater. For nonpoint N sources (agricultural and natural ecosystems), calculations are based on local hydrology, climate, geology, soils, climate and land use combined with data for 1995 on crop production, N inputs from N fertilizers and animal manure, and estimates for ammonia emissions, biological N fixation, and N deposition. For point sources, our estimates are based on population densities and human N emissions, sanitation, and treatment. The results provide a first insight into the magnitude of the N losses from soil-plant systems and point sources in various parts of the world, and the fate of N during transport in atmosphere, groundwater, and surface water. The contribution to the river N load by anthropogenic N pollution is dominant in many river basins in Europe, Asia, and North Africa. Our model results explain much of the variation in measured N export from different world river basins.

Efecto de la adición de proteínas de suero sobre la elaboración y la calidad del queso cremoso argentino / Effect of the increase of the milk proteins in quality of argentine milk

Realizó un estudio en laboratorio y planta piloto acerca de lai nfluencia del agregado de ricota (proteínas de suero) sobre la tecnología, las características organolépticas y el rendimiento del queso Cremoso Argentino.

[Trials of cheese-making using concentrated bacterial starters]. / Ensayos de elaboración de quesos con fermentos bacterianos concentrados.

Studies about cheese preparation with frozen and concentrated bacterial starters have been carried out. The Pategras cheeses were obtained from raw milk. The starters were prepared with a selected strain of Streptococcus lactis, concentrated until reaching a value of 3.10(9) colony forming units/ml and resuspended in milk previously supplemented with 8% of yeast extract. These concentrates were frozen at -40 degrees C and kept at -20 degrees C for 60 days. Three kinds of starters were tested: one thawed by placing the flask in a 40 degrees C water bath, another added to the cheese vat without previous thawing and a control sample prepared in steamed reconstituted milk. In order to evaluate the convenience of each technique several chemical and microbiological analysis were performed during the preparation (Table 1 and 2) and the ripening of the cheese (Table 3). The results have showed that the direct use of thawed frozen concentrates in the cheese vat allows the obtaining of high quality cheese. On the other hand, the technique based on thawing through a water bath did not lead to good results.

Ensayos de elaboración de quesos con fermentos bacterianos concentrados / Assays of cheese preparation with concentrated bacterial starters

En el presente trabajo se llevaron a cabo estudios de elaboración de quesos con fermentos bacterianos concentrados y congelados. Los citados quesos, de pasta semicocida, se obtuvieron a partir de leche pasteurizada. Los fermentos se preparaon con una cepa seleccionada de Streptococcus lactis, concentrada hasta alcanzar un valor de 3.10**9 U.F.C./ml y resuspendida en lecha adicionada con el 8% de extracto de levadura. Dichos concentrados se congelaron a -40- y se almacenaron a -20-C durante 60 días. Se ensayaron tres varianes de fermento: uno descongelado en baño María a -40-C, otro agregado a la tina quesera sin previo descongelamiento y un testigo preparado en leche reconstituída estéril. Con el objeto de evaluar la conveniencia del empleo de dichas variantes, se realizaron análisis químicos y microbiológicos durante el proceso de elaboración y maduración de los quesos. Los resultados obtenidos han demostrado que el empleo de concentrados congelados descongelados directamente en la tina, permite obtener quesos de muy buena calidad. No sucedió lo mismo con los descongelados en baño María, lo que torna desaconsejable esta tecnología

[Obtaining beta-galactosidase using whey]. / Obtención de beta-galactosidasa usando suero de leche.

The search of a microorganism with the ability to produce the enzyme beta-galactosidase was undertaken according with the requirements of the market, in economical, technological and sanitary terms. The process consisted of recovery and use of the effluent from milk and cheese used to feed pigs, producing at the same time different types of contamination; once investigated and adjusted the technological variables to produce the enzyme, and selected the most convenient microorganism for such purpose the acting upon the extraction, conservation and purification of the product were adjusted. Comparative results of conversion were obtained with different test, at laboratory scale and industrial plants, in similar conditions to those obtained with importation products.

Obtencion de beta-galactosidasa usando suero de leche. / Production of beta-galactosidase using milk whey

En este trabajo se ha buscado un microorganismo capaz de producir la enzima beta-galactosidase, con el fundamento de necesidades de mercado, ya sean economicas, tecnologicas o sanitarias. El proceso, que aqui describimos en sus rangos esenciales, considera: a) Recuperacion y aprovechamento para esta finalidad, del efluente de plantas lactocasearias que, muy parcialmente se una para la crianza de cerdos, contaminando ambientes en su mayor cuantia b) Investigadas y ajustadas la variables tecnologicas de produccion de la enzima, una vez seleccionado el microorganismo mas apto para tal fin, finalmente se procedio a: C) Ajustar las variables que influyen los procesos de extraccion, conservacion y purificacion del producto obtenido. Diversas pruebas a escala de laboratorio y en plantas industriales lograron resultados de conversion equiparables, en condiciones similares, a los obtenidos con productos de importacion provenientes de las mas sofisticadas tecnologias

[Production of a concentrate of Mucor bacilliformis acid protease]. / Produccion de un concentrado de proteasa ácida de Mucor bacilliformis.

A concentrate of milk-clotting enzyme was produced by culture of Mucor bacilliformis on wheat bran medium moistened to 120% water on dry bases with HC1 2 N solution. The wheat bran was autoclaved, spread on trays and inoculated with 5.10(6) spore/gr of dry bran. After 10 days of culture at 21 degrees C, the enzyme produced was extracted with water and adjusted to pH 4.4. The precipitation was performed with ethanol. The precipitate was dissolved in HCl solution (pH 4.5) and it was concentrated by dialysis against polyethylene glycol 20.000. The enzyme solution had a specific activity of 1123 units/mg. and it was tested in the elaboration of cream cheese.

Produccion de un concentrado de proteasa acida de Mucor bacilliformis. / Production of an acid protease concentrate from Mucor bacilliformis

Se obtuvo un concentrado de enzimas congulantes de leche por cultivo de Mucor bacilliformis en afrecho de trigo humectado a 120% de agua sobre base seca con solucion de HC1 0,2 N. El afrecho esterilizado fue dispuesto en bandejas, e inoculado con 5.10 (6) esporos/gr de afrecho seco. Luego de 10 dias de incubacion se extrajo el afrecho enmohecido con agua, se ajusto el pH a 4,4 y se precipito el sobrenadante limpido con etanol. El precipitado fue disuelto en agua clorhidrica (pH 4,5) y concentrado por dialisis contra polietilenglicol 20000. La solucion con una actividad especifica de 1128 U/mg, se utilizo en dos ensayos de elaboracion de queso tipo cremoso