The effect of the hygienic quality of milk on changes in microbial counts and biogenic amine content was evaluated during ripening of goat cheeses manufactured from pasteurized and raw milks at 1, 14, 30, 60 and 90 d. The original milk, rennet, curd and whey were also included in the study. The pH, salt content and extent of proteolysis in the cheese were also evaluated. Spermidine and spermine were the main amines in raw milk, while they were minor amines in cheeses. Other amines increased markedly during ripening, tyramine being the main amine in cheese made from raw milk and cadaverine and putrescine in those produced from pasteurized milk. Enterobacteriaceae counts decreased during ripening whereas those of lactic acid bacteria increased, especially lactobacilli and enterococci. Cheese made from raw milk showed higher microbial counts during ripening than those made from pasteurized milk, especially for Enterobacteriaceae and enterococci, counts being 2 or 3 log units higher. Raw milk cheese showed remarkably higher biogenic amines compared with pasteurized milk cheeses. Therefore, pasteurization of milk causes a decrease in final biogenic amine content of cheese as a result of the reduction of its microbial counts.

The objective of this research was to determine the effect of exopolysaccharide (EPS) production by lactic acid bacteria on the microstructure and rheology of Karish cheese, a soft acid coagulated cheese made using skim milk. An EPS-producing strain of Streptococcus thermophilus, and its EPS non-producing genetic variant were used to make comparable batches of the cheese. EPS in cheese was visualized by cryo-SEM as a large, dense, filamentous mass. Cheese made with the EPS non-producing culture was characterized by a dense protein network with smaller pores compared to that prepared with the EPS-producing culture. High elastic and viscous moduli measured by dynamic rheology were observed for EPS negative cheese and was attributed to its dense protein network. Creep test experiments demonstrated that cheese prepared with the EPS non-producing strain was more rigid and recovered its deformation, while cheese made using the EPS producing culture was more deformable. These results indicate that EPS-producing cultures can improve the physical properties of Karish cheese by reducing undesirable rigidity.

This work studied the addition of an adequate lipase to enhance lipolysis reactions and the development of piquant flavour and sharp odour in Idiazabal cheese, as an alternative to the use of lamb rennet paste. Cheeses were manufactured from bulk raw ewes' milk in 50 l vats with commercial bovine rennet and 80 lipase units of pregastric or 180 lipase units of fungal lipase and ripened for 180 days. A higher lipolytic activity was induced by lipase addition promoting strong changes in odour and flavour attributes. Both fungal and pregastric lipases increased the content of total free fatty acids (FFA), but the fungal lipase released mainly medium- and long-chain FFA. In contrast, the pregastric lipase preferably released short-chain FFA. Diglyceride (DG) content was considerably higher in cheeses made with added pregastric lipase compared with those made with fungal lipase or with no lipase. Monoglycerides (MG) were detected only in cheeses made with either lipase added, reaching comparable concentrations after ripening for 180 days. The cheeses made with pregastric lipase had the highest scores for odour and flavour intensity, and sharp and rennet odours, desirable attributes for the Idiazabal cheese made with lamb rennet paste. None of the texture attributes were significantly influenced by the concentrations of MG and DG in the cheeses made with either lipase. Thus, the pregastric lipase was more appropriate than the fungal lipase to develop a more traditionally-flavoured Idiazabal cheese.

The teat canal is an invagination of the outer teat surface. Its epithelial constitution is, however, highly specialized as indicated by its high turnover rate, its unique function in trapping bacteria, and in sealing the teat canal between milkings. The keratin of the teat canal is in a dynamic state of generation and degradation. Repeated removal during milking of keratin contaminated with or colonized by bacteria plays a significant role in preventing mastitis (Murphy, 1959; Capuco et al. 1992). To study the biology of the keratin lining, e.g., its turnover, and its relation to mastitis defence, reliable methods of collecting keratin in vivo for quantitative and qualitative analysis are necessary. Bright et al. (1990) compared methods for keratin collection in vivo and suggested that a tapestry needle was a suitable tool for collecting repeatable, representative samples of keratin for lipid analysis from single teat canals of living cows.

In some European regions ewes' milk is transformed into cheese without a previous heat treatment. The microbiota and the native enzymes present in raw milk are considered to be responsible for the characteristic strong flavour of raw ewes' milk cheeses (Nuñez et al. 1989). Although pasteurization ensures a higher uniformity of the product, heat treatment of ewes' milk may impair the sensory characteristics of cheeses (Gaya et al. 1990).

The lactic acid bacteria (LAB) play an important role in the production of fermented foods. The development of concentrated cultures of LAB, for inoculating the production vat directly (bulk starters), has eliminated many problems traditionally involved in their preparation and maintenance by the food industry. For industrial use, LAB are often preserved in a frozen or dried form, the latter preparations having lower transport and storage costs (Kets et al. 1996). Dried cultures, however, lose viability/activity during storage, especially when kept at room temperature (Champagne et al. 1991; Teixeira et al. 1995a,b; Castro et al. 1996). Attempts to improve the survival of LAB during drying have already been tried (Linders et al. 1997b; Gardiner et al. 2000). Previous results indicated a direct relationship between the presence of compatible solutes in LAB and their ability to survive drying conditions. Such solutes include amino acids, amino acid derivatives, quaternary amines, sugars and tetrahydropyrimidines (Kets & De Bont, 1994; Kets et al. 1994, 1996).

Arthur Samson Foot was born on the family dairy farm in South Dorset, where he gained practical farming and management skills. Much in his career has shown the importance of this background. He always strived to relate his science to practice. He was proud of his roots, and seldom happier than when on a farm.

During a study on the effect of addition of monovalent and divalent salts on the apparent viscosity of sodium caseinate solutions (Carr et al. 2002) it was discovered that many of the high viscosity solutions appeared to gel when refrigerated. Furthermore this cold gelation was found to reverse on heating. The phenomenon of reversible cold gelation of caseinate solutions has not been reported. The most well known example of reversible cold gelation is gelatin solutions, but a number of polysaccharides also form gels on cooling, e.g. agarose, pectin and carrageenan (Evans & Wennerstrom, 1994). Whey proteins also gel at 25 °C in the presence of calcium ions, though not in their absence, and this gelation is not reversible (Barbut & Foegeding, 1993).