No abstract

SummaryThe vitamin content of ultra-high-temperature (UHT) processed milk was compared with that of the original raw milk. Three processes were used. In the first, which caused no change in oxygen content, the milk was heated and cooled in a plate-type heat exchanger. In the second, the milk was again heated indirectly and then evaporatively cooled, leaving in the milk about one-third of the initial oxygen content. In the third process the milk was heated by direct steam injection and cooled by evaporation and contained little or no residual oxygen.On processing and during subsequent storage for 90 days there was no loss of vitamin A, carotene, vitamin E, thiamine, riboflavine, pantothenic acid, biotin or nicotinic acid. There was little or no loss of vitamin B6or vitamin B12on processing, but up to 50% of each of these vitamins was lost during 90 days' storage. All the dehydroascorbic acid (DHA) and about 20% of the ascorbic acid (AA) was lost on processing. There was no further loss of AA during 90 days’ storage when no residual oxygen was present, but in milks containing more than about 1 ppm oxygen all the AA was lost within 14 days. About 20% of the folic acid was lost on processing; thereafter, as with ascorbic acid, the extent of the loss on storage depended on the residual oxygen content of the milk: in the absence of oxygen the folic acid was stable.

I. The flow of digesta through the duodenum and the concurrent secretion of the pancreas were studied in four Friesian calves given four milk-substitute diets. The diets were: reconstituted, 'mildly' pre-heated, spray-dried skim-milk powder with (SKF) or without (SK) margarine fat or with 5 0 yo of the skim-milk powder in diet S K F replaced by soya-bean flour (ASKF) or fish-protein concentrate (BSKF), together with dried whey. The diets were given ad lib. twice daily from 13 to 37 d of age, each diet being given for 6 consecutive days. Collections of duodenal digesta and pancreatic secretions, from cannulas, were made for 12 h after feeding the 6th and 12th meals ('experimental' meals) for each diet.2. The diets fed as 'experimental' meals contained polyethylene glycol (PEG) as a fluid (whey) marker and goat's milk containing [*H]lysine as a marker for total protein; 8-carotene was added as a lipid marker to the three diets containing margarine fat.3. Over the 12 h postprandial period, the patterns of duodenal digesta flow and secretion of pancreatic fluid did not differ markedly between the four diets. The abomasal outflow of both nitrogen and lipid in a 12 h postprandial period was related to their intakes from the 'penultimate' (5th and 11th) meals for diets S K F and SK but to their intakes at the 'experimental meals' for diets ASKF and BSKF. Secretion of pancreatic enzyme activity was highest during the 1st hour after feeding but the main outflow from the abomasum of total N and lipid occurred 5-10 h after feeding.4. The time required for all the whey marker (PEG) to pass through the duodenum was similar for diets SKF and SK, but only 53 and 42 % respectively of the ingested protein marker passed through the duodenum in the 12 h after feeding. More acid appeared to be secreted by the abomasum when diet SK was given; also less undigested protein passed out of the abomasum after giving this diet. It is concluded that the physical absence of fat globules in the abomasal clot increases the degree of proteolysis. 5. The secretions of pancreatic fluid and pancreatic enzyme activity were all markedly lower for diet SK than for diet SKF.6. With diets containing non-milk proteins (ASKF and BSKF), abomasal proteolysis was less efficient and the ingested protein passed out of the abomasum more rapidly than for diet SKF. There was no difference in the rate of abomasal outflow of the whey fluids between diets SKF, ASKF and BSKF.7. In comparison with diet SKF, diets ASKF and BSKF tended to induce less pancreatic enzyme secretion over a 12 h postprandial period, with the exception of lipase.8. There appeared to be no direct relationship between the quantities of any of the pancreatic enzymes secreted during a postprandial period and either the concurrent flow of duodenal digesta or the total quantities of dietary constituents passing through the duodenum. J. H. TERNOUTH AND OTHERS I975Ternouth, Roy & Siddons (1974) showed that the composition of milk-substitute diets affected the secretion of pancreatic enzymes by calv...

A study has been made of methods using 2,4-dinitrophenylhydrazine (DNPH) or 2,6-dichlorophenolindophenol (DCP) for the determination of vitamin C (ascorbic acid-)-dehydroascorbic acid) in raw, UHT processed, evaporated and sterilized milk.Interfering substances were not detected in milk that had received a heat treatment no more severe than 145 °C for 4 s (UHT process), so that either reagent could be used.With more drastic heat treatment, interfering substances were formed and only the DNPH method with column and thin layer chromatography of the DNPH derivatives was specific for vitamin C. With in-bottle sterilized milk, the values for ascorbic acid were (in mg/100 ml) 1-16 (DCP method with H 2 S reduction); 0-58 (DCP method with Escherichia coli reduction); 0-64 (DNPH method); 0-33 (DNPH method combined with chromatography).In our experience the DNPH method combined with chromatography of the derivatives is highly specific for vitamin C and should be used to check the results obtained by other and simpler methods.

SummaryA comparison was made of the effects of direct and of indirect ultra-high-temperature (UHT) processing of milk, under standardized operating conditions giving equal sporicidal effects, on some of the more labile water-soluble vitamins and on vitamin A and carotene. The effects of processing per se were negligibly small, and the method of processing was important only in so far as the presence of residual oxygen in the sterilized milk has been found to cause losses of folic acid and ascorbic acid during storage subsequent to sterilization. The incorporation of a de-aerator vessel, to reduce the oxygen level in the indirectly heated milk and so eliminate the adverse effects of oxygen during storage, had no effect on the vitamin loss occurring during heat treatment. It is concluded that milk produced by indirect heating plant incorporating a de-aerator should be similar in vitamin content to milk produced on a direct heating plant, both immediately after processing and after storage.