The presence in the bovine mammary gland of a desaturase specific for the conversion of stearic to oleic acid allows the manipulation of the physical properties of milk fat by varying the dietary intake of c 1 6 and CIH fatty acids. In particular, feeding the dairy cow an oil with a high C1ti:Cni ratio should allow the proportion of milk fat that is liquid at 5 'C to be increased, with a consequent improvement in the low-temperature spreadability of butter. In this paper, the effect of feeding concentrate rations containing (a) soya oil as the free oil and as cracked soya beans; (b) various levels of soya oil, the ration being offered twiceor 24-times daily, on the thermal properties of the milk fat and on the yield of milk constitiients is examined in detail. Feeding ratios containing free soya oil greatly increased the proportion of milk fat liquid at 5 C , whereas cracked soya oil gave only slight increases. Proportion and yield of milk fat were decreased by feeding soya oil twice daily but were increased by continuous feeding.

SummaryThe effects of supplementing a basal diet, in which the low level of fatty acids limited milk production, with soya oil, a palm oil/palmitic acid mixture and tallow, on the yield of milk and of its constituents, and on the composition of the milk, are reported. The yields of milk and milk fat were greatly increased by all the oil-supplemented diets; the mean daily yield of solids-not-fat (SNF) was also increased, but supplementation with soya oil caused the yield of crude protein (CP) to decrease, whereas the other fat-rich concentrate mixtures gave the same mean yield of protein as did the low-fat, control diet. All 3 oil-supplemented diets lowered the proportion of CP in the milk, but the SNF content was unchanged by any treatment. Dietary soya oil tended to lower the proportion of fat in the milk, whilst the palm oil/palmitic acid mixture raised it, with the tallow exerting no effect. The results are discussed in relation to previous work in which these dietary oils have been used, but in which the intake of fatty acids from the control diets did not limit milk production to the extent reported here.

Eight sheep fitted with both rumen and duodenal re-entrant cannulae were used to investigate the digestion of a diet consisting of 60% molassed sugar beet pulp and 40% ground barley. Molar proportions of acetic acid in the rumen varied from 55 to 66%, of propionic acid from 15 to 26% and of butyric acid from 12 to 19%. On average,69.1* 1.2% of the dietary organic matter was digested in the rumen and 89.9 k 0.4 % in the whole digestive tract. Corresponding figures for gross energy were64.~k1.4%and87.4f0.4%,forcellulose 82.8k1.4%and86.3+0.8% and for a-linked glucose polymers were 91.6 f 0.9 % and 100 k 0 %. There were only small differences in the extent of digestion of these constituents in the rumen between animals and the mean production of total short-chain fatty acids was 55.5 k 1.6 % of the digestible energy.The mean daily amount of nitrogen entering the duodenum was 11.1 If: 5.1 % greater than the dietary intake and the apparent digestibility of nitrogen was 76.7 k 1 .Ox.Calculation of bacterial protein using z-c-diaminopimelic acid as a marker, indicated that bacterial protein constituted about 80% of the total protein entering the duodenum and that the average efficiency of rumen protein synthesis was 14.31 f 0.75 g crude protein/100 g OM "disappearing" in the rumen. With the exception of one animal in which the rumen ammonia concentration was especially high, the efficiency of protein synthesis varied between animals over only a narrow range and there was no evidence. that efficiency was influenced by variation in the pattern of fermentation in the rumen.

The effect of pH adjustment, calcium removal and citrate addition on the stability of a cream liqueur at 45°C was investigated. Evidence is presented to show that by either removal or sequestration of ionic calcium the shelf life of cream liqueurs can be usefully extended. Data is included on the relation between viscosity and composition for a range of liqueurs.

The properties of cream liqueurs with either sorbitol or sucrose as the principal carbohydrate have been investigated in detail. Not only does the use of sorbitolmodify the organolepticproperties of the liqueur but its use also promotes a signijicant increase in shelf-life of the product. In addition, a simple one-stage process for the manufacture of cream liqueurs is described andhas been compared with a typical two-stage technique.Although a comprehensive range of cream liqueurs has appeared on the world market the technology of cream liqueur production is in its infancy, and most information on formulation and stabilization is in proprietary hands. In a general article, the principles of cream liqueur formulation and compositional analyses of the most successful range of liqueurs were outlined (Banks, Muir & Wilson, 1981a). Subsequently, extension of the shelf-life of cream liqueurs at high ambient temperatures was studied, and the effects of pH adjustment, calcium removal, and calcium ion sequestration were investigated in detail (Banks, Muir & Wilson, 1981 b). This work showed that the ionic calcium present in cream has a detrimental effect on the quality of cream liqueurs and that, either by removal or sequestration of the calcium, the shelf-life could be greatly enhanced.In preliminary evaluation of the organoleptic properties of cream liqueurs, it was noted that the use of sorbitol as the major carbohydrate in cream liqueurs markedly changed the flavour and mouthfeel of the product (Banks et ai., 1981a). For this reason, further studies were carried out and are reported here.In addition, efforts were made to streamline the process of manufacture of liqueurs, and, as a result, a simplified method for liqueur production was also developed. EXPERIMENTAL MATERIALS AND METHODSFreshly pasteurized double cream (48 per cent butterfat) was prepared on site or purchased from a local creamery. In both cases, the cream was heat-treated at 80°C for 16 s.Sodium caseinate was bought from the Scottish Milk Marketing Board (Underwood Road, Paisley) and sucrose and sorbitol from local retail outlets.Neutral spirit, malt, and blended Scotch whiskies were gifted by various distillers.The tri-sodium citrate used in this work was Analar grade reagent.