RESUMEN
Ricotta cheese, particularly the ovine type, is a typical Italian dairy product obtained by heat-coagulation of the proteins in whey. The aim of this work was to investigate the influence of whey protein concentration, obtained by ultrafiltration, on yield of fresh ovine ricotta cheese. Ricotta cheeses were obtained by thermocoagulation of mixtures with protein content of 1.56, 3.10, 4.16, and 7.09g/100g from the mixing of skim whey and ultrafiltered skim whey. A fat-to-protein ratio of 1.1 (wt/wt) was obtained for all mixtures by adding fresh cream. The initial mixtures, as well as the final ricotta cheeses, were analyzed for their composition and by SDS-PAGE. Protein bands were quantified by QuantityOne software (Bio-Rad, Hercules, CA) and identified by liquid chromatography-tandem mass spectrometry. Significant differences in the composition of the ricotta cheese were observed depending on protein concentration. Particularly, ricotta cheese resulting from the mixture containing 7.09g/100g of protein presented higher moisture (72.88±1.50g/100g) and protein (10.18±0.45g/100g) contents than that prepared from the mixture with 1.56g/100g of protein (69.52±1.75 and 6.70±0.85g/100g, respectively), and fat content was lower in this sample (12.20±1.60g/100g) compared with the other treatments, with mean values between 15.72 and 20.50g/100g. Each protein fraction presented a different behavior during thermocoagulation. In particular, the recovery of ß-lactoglobulin and α-lactalbumin in the cheese increased as their content increased in the mixtures. It was concluded that concentrating ovine rennet whey improved the extent of heat-induced protein aggregation during the thermal coagulation process. This resulted in a better recovery of each protein fraction in the product, and in a consequent increase of ricotta cheese yield.
Asunto(s)
Queso/análisis , Manipulación de Alimentos/métodos , Proteínas de la Leche/química , Animales , Cromatografía Liquida , Quimosina/química , Grasas de la Dieta/análisis , Proteínas en la Dieta/análisis , Electroforesis en Gel de Poliacrilamida , Calor , Concentración de Iones de Hidrógeno , Lactalbúmina/análisis , Lactoglobulinas/análisis , Proteómica , Ovinos , Espectrometría de Masas en Tándem , Ultrafiltración , Proteína de Suero de LecheRESUMEN
PIP: The authors present a brief statistical summary of recent data on intra-European migration, identify the major problems created by the present situation, and define some main lines of approach concerning the future of European labor migration^ieng
Asunto(s)
Emigración e Inmigración , Empleo , Estadística como Asunto , Migrantes , Demografía , Países Desarrollados , Economía , Europa (Continente) , Fuerza Laboral en Salud , Población , Dinámica PoblacionalAsunto(s)
Niño , Cultura , Educación , Directrices para la Planificación en Salud , Lenguaje , Migrantes , Adolescente , Factores de Edad , Comunicación , Demografía , Países Desarrollados , Emigración e Inmigración , Europa (Continente) , Agencias Internacionales , Población , Características de la Población , Dinámica PoblacionalRESUMEN
PIP: This article represents the text of a paper presented at a conference on European migration organized by the Council of Europe in Strasbourg, May 6-8, 1979. The authors examine changes in European migration since the oil crisis of 1974 and include a review of the relevant statistical data, a review of the main problems, and a summary of some possible future trends in European migration^ieng