The determination of lactic acid in milk

Ling, E. R.

doi:10.1002/jsfa.2740020608

Cited by 18 publications

(4 citation statements)

References 7 publications

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“…The cannulas were connected directly and continuously to an automatic analyser according to a procedure described elsewhere (Aumaitre et al 1975). Total reducing sugars (Hoffman, 1937), true glucose (glucose oxidase technique; Hill & Kessler, 1961), fructose (Roe, 1934) and lactic acid (Ling, 1951) were determined either simultaneously or separately according to the type of studies made. In order to avoid excessive removal of blood, the number of simultaneous analyses in one and the same animal was restricted, explaining the different number of observations reported.…”

Section: Measurementsmentioning

confidence: 99%

Absorption kinetics of some carbohydrates in conscious pigs

1984

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1. Concentrations of reducing sugars, glucose, fructose and lactic acid in blood obtained from arterial and portal catheters were measured for periods of 8-24 h in twenty-three unanaesthetized pigs (mean body-weight 50 kg). From 6 to 8 d after implantation of catheters, the animals received experimental meals containing different levels (400, 800, 1200, 1600 g respectively) of different sugars (glucose ten meals, sucrose eighteen meals, lactose nine meals, maize starch sixteen meals) as well as a protein-mineral-vitamin premix.2. After each meal the reducing sugars appeared in the portal blood in successive waves. The porto-arterial differences in the concentration of reducing sugars, representing the real appearance of sugar-hydrolysis products in the animal, varied greatly according to the sugar ingested and its level of intake. For each level of intake, these differences were larger, but of shorter duration, for glucose and sucrose than for maize starch. For these three carbohydrates, the higher the level of ingestion, the larger and the more persistent the porto-arterial differences. Lactose represented a special case, as the porto-arterial differences of reducing sugars were always much lower than those obtained with the other sugars and they did not vary with the level of intake.3. Our findings show that the products formed by feeding glucose and sucrose appear more rapidly in the portal blood than those formed by feeding lactose. Accordingly, the length of time of digestion of glucose and sucrose is shorter than that of maize starch and lactose.Sugars ingested by man and monogastric animals are mainly polysaccharides although, in certain circumstances, disaccharides and even monosaccharides are also ingested. In the pig, dietary energy generally comes from cereal starch, but sometimes from industrial by-products such as whey or molasses which contain other types of carbohydrate (lactose, sucrose). However, use of dietary sugars, such as lactose (FCvrier, 1969) or sucrose (Brooks & Iwanaga, 1967; Aherne et al. 1969), does not lead to the same results especially for growth and nitrogen retention; in addition, their influence is variable according to age (Ekstrom et al. 1975). As the supply of energy-giving nutrients at the sites of protein synthesis should synchronize with the supply of amino acids to make the synthetic process optimal (Elman, 1953), variations in the nutritive value of sugars might be due to a different chronology in their digestion and in the absorption of their hydrolysis products, as well as to the different nature of the latter. Until now, estimation of the amounts of nutrients available for the animal during digestion was made by means of the digestibility method which allows the disappearance of nutrients during their oral-aboral transit to be measured but does not quantify the precise kinetics of their appearance in the organism and their transformation during transit and absorption. These kinetic aspects of the appearance of nutrients in the animal may be estimated from the enric...

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Section: Measurementsmentioning

confidence: 99%

Absorption kinetics of some carbohydrates in conscious pigs

1984

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“…The initial lactic-acid content of fresh milk is known to vary (3,6,7,10), and the recovery of lactic acid is only 80-90% (3). It was therefore decided that a solution of lithium lactate in water was a more reliable standard.…”

Section: Preparation Of Standard Lactic-acid Curvementioning

confidence: 99%

693. A rejection test for raw milk

Taylor

Clegg

1958

Journal of Dairy Research

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The determination of apparent lactic acid has been used as a basis for a rejection test for raw milk. The method consists of precipitation of milk proteins with barium chloride, sodium hydroxide and zinc sulphate, and the addition of ferric chloride to the filtrate to produce the yellow colour of ferric lactate. Lactic acid is not solely responsible for the production of the yellow colour, which, nevertheless, gives a good relationship with keeping quality of milk (measured as hours to the C.O.B. end-point at 22° C.) and the values have been expressed as ‘apparent lactic acid’.The relationship of winter and summer milks to keeping quality has been studied, and a value of 0·03% apparent lactic acid in milk is equivalent to an average keeping quality of 5¾ and 8½ hr. for winter and summer milks, respectively. A value of 0·03% is recommended as the earliest value of apparent lactic acid at which milk could be rejected.The apparent lactic acid in colostrum and late-lactation milk and in milk from cows suffering from mastitis has been determined, and only in late-lactation milk were the values found to be significantly higher than usual in fresh raw milk, and an inverse relationship between yield and apparent lactic acid is suggested.Permanent glass matching disks have been prepared for use in a Lovibond comparator. This permits the intensity of the yellow colour produced with 1% ferric chloride to be determined and the apparent lactic acid in milk estimated.Grateful acknowledgement is made to the management and staff of the Dairy Department of the Reading Co-operative Society and the Farmer's Clean Milk Dairy, Reading, and local milk producers for supplying samples for experiments; to the N.M.T.S. staff in Reading for help in finding suitable farmers, and to the Dairy Husbandry Department of the N.I.R.D. for information about and samples of abnormal and late-lactation milk. Our particular thanks are due Miss Marie Gruber for technical assistance, to Dr N. J. Berridge for the suggestion and help on the work on pH change as an indication of keeping quality (given in the appendix), and to Dr A. T. R. Mattick for the advice given in this work.

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“…Rapid methods for the determination of citric acid (6) and lactic acid (109) in dairy products and in grape juice and wine (98) have been proposed. Methods of separation of several nonvolatile carboxylic acids (25) and lower fatty acids (187) by chromatographic technique have been described.…”

Section: Chemistrymentioning

confidence: 99%