A Colorimetric Method for the Estimation of Reducing Groups in Milk Powders

Chapman, R. A.; McFarlane, William

doi:10.1139/cjr45b-012

Cited by 30 publications

(6 citation statements)

References 13 publications

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“…The TBA and FR values observed for skim-milk powder are indicative of the progress of Maillard browning during storage and are in agreement with the trend noted by Chapman & McFarlane (1945). The results of the present study do not however, clarify the contribution of Maillard browning to specific off-flavours in skim-milk powder.…”

Section: Discussionsupporting

confidence: 75%

“…The TBA test relies upon the formation of a coloured complex between TBA and hydroxymethylfurfural, which is a key intermediate in the browning sequence (Keeney & Bassette, 1959). This test is more specific for Maillard browning than the FR test, which was originally developed to measure protein denaturation by the ability of liberated sulphydryl groups to reduce potassium ferricyanide (Chapman & McFarlane, 1945). Subsequently, Lea (1947) showed that in skim-milk powder ferricyanide was also reduced by products formed by the protein-catalysed degradation of lactose.…”

Section: Discussionmentioning

confidence: 99%

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Flavour defects in edible casein and skim-milk powder: I. The role of Maillard browning

Walker¹

1972

Journal of Dairy Research

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TWO chemical tests were used to measure the extent of lactose degradation by Maillard browning in casein and skim-milk powder during storage. At the same time these products were evaluated organoleptically. Highly significant correlations between age, flavour score and level of browning in skim-milk powder were in contrast to the lack of any relationship between the flavour score or age of casein and its level of browning. Maillard browning occurring during storage of skim-milk powder was accompanied by increasing levels of cereal and malty flavours. A stale flavour, which closely resembled the musty flavour common to casein, was not observed in skim-milk powder until after storage for 9 months. A distinct difference in the flavour stability of rennet casein and acid casein could not be accounted for in terms of the relative extent of lactose degradation. Evaluation of casein samples with different lactose contents suggested that Maillard browning does not contribute to flavour defects during storage unless the curd is so insufficiently washed during manufacture as to produce an abnormally high level of lactose in the dried product.For many years commercial casein has been used primarily in the preparation of paper coatings, adhesives and plastics, with the result that properties such as viscosity, adhesive strength, solubility and ability to bind water and pigments have received considerable attention. Recently, however, the more widespread use of casein as a high-quality protein in compounded foods has required a more searching evaluation of its flavour stability.A common defect in casein may be described as a musty or stale flavour, which is sometimes detectable immediately following the drying of fresh casein curd and which becomes more pronounced during storage. Organoleptic evaluation of many casein samples has demonstrated that the musty flavour is intensified by heattreatment and that acid-precipitated caseins are considerably more susceptible to musty flavour development than are caseins precipitated by rennet.In 2 recent publications, Australian workers have investigated the nature and origin of the so-called 'gluey' flavour in casein and co-precipitates. In the first study, Ramshaw & Dunstone (1969 a) demonstrated positive correlations between gluey flavour, lactose content and the extent of Maillard browning as measured by the ferricyanide reducing value. Furthermore, the gluey flavour was not detectable by 15-2

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Section: Discussionsupporting

confidence: 75%

Section: Discussionmentioning

confidence: 99%

Flavour defects in edible casein and skim-milk powder: I. The role of Maillard browning

Walker¹

1972

Journal of Dairy Research

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“…Steinberg (1959) reported an increase in reducing substances in stored freeze-dried beef. Chapman and McFarlane (1945) also observed the accumulation of reducing substances in milk powders and isolated milk proteins stored in air. The nature of these reducing compounds is unknown but they are generally considered to indicate protein deterioration.…”

mentioning

confidence: 85%

Lipid autoxidation in freeze-dried meats

Chipault¹,

Hawkins²

1971

J. Agric. Food Chem.

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The rapid absorption of oxygen and appearance of off-odors in freeze-dried meats indicate that oxidative deterioration occurs.However, no peroxides were found and changes in spectral absorption of the fat, thiobarbituric acid reactive substances, and reducing capacity of the dried meats were small and could not be correlated with the absorption of oxygen. Of the several objective methods studied, oxygen absorption was the only one that could be used to indicate oxidation. Freeze-dried beef and chicken have been fractionated into their lipid and nonlipid components. The absorption of oxygen by the isolated fractions has been compared to that of the whole tissues. Autoxidation of freeze-dried meats takes place in two stages. The protein-bound lipids autoxidize first, without an induction period, and their initial rate of autoxidation decreases with time. After a period of lower oxygen absorption, the free glyceride fat begins to autoxidize in the autocatalytic manner characteristic of autoxidation in isolated glyceride fats.4 utoxidation of lipid is a serious cause of deterioration /A in freeze-dried meat. Lea (1943) recognized two types of defects in stored freeze-dried meats: a tallowy or oily flavor due to fat oxidation; and a mealy defect ascribed to deterioration of nonfat components.In studies with freeze-dried beef, Tappel ( 1956) and El-Gharbawi and Dugan (1965) found that protein-bound lipids autoxidized readily, whereas the free glyceride fat was very stable. In addition, Tappel (1956) reported that protein could account for 50 to 100% of the total oxygen absorbed by freeze-dried beef. However, Lea et al. (1958) observed that the residual protein of defatted herring meal did not oxidize readily.

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“…Acid-ferricyanide-reducing substances. The method of Chapman & McFarlane (1945) as modified by Crowe, Jenness & Coulter (1948) was used. The milk was diluted 1 in 10 with distilled water and immediately added to the buffered ferricyanide.…”

Section: Methodsmentioning

confidence: 99%

Certain non-biological properties of sterilized milk in relation to the treatment of the milk and the temperature of heating

Higginbottom

Taylor

1960

Journal of Dairy Research

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The effect of the temperature of laboratory sterilization of homogenized milk on the titratable acidity, the colour of the milk, the yellowing of the filtrate from the Aschaffenburg turbidity test, the acid-ferricyanide-reducing substances and on pH has been determined. The greater changes in these properties in milk sterilized under reduced oxygen tension compared with milk sterilized in open bottles was shown to be due, in part at least, to the slower rate of cooling in the evacuated bottles. Samples of commercial sterilized milk have also been examined and their properties have been compared with those of the sterilized milk produced in the laboratory.The ability of spores of the genus Bacillus to germinate and multiply in sterilized milk has been shown by Higginbottom & Taylor (1960 a) to depend in part on the treatment of the milk before and after sterilization. Concurrent with this work, certain non-biological properties of the sterilized milk were examined and considered in relation to the growth in such milks of spores of bacilli. The effect of sterilization under varying conditions on pH, titratable acidity, acid-ferricyanide-reducing substances, the colour of the nitrate in the Aschaffenburg turbidity test and the colour of the milk are reported in this paper. The effect on oxidation-reduction potential will be dealt with in another paper (Higginbottom & Taylor, 19606). These properties have all been followed in the same samples of milk in order to compare the changes caused by the different treatments of the milk and to associate these changes with the rate of bacterial growth. METHODSTitratable acidity. 25 ml sterilized milk were titrated with jsr/9 NaOH to pH 8-60 using a direct reading pH meter in conjunction with a glass electrode and a saturated calomel reference electrode. Results are reported as ml N/9 NaOH/10 ml milk. pH. A direct reading pH meter was used with a glass electrode. Turbidity test. The method of Aschaffenburg (1947) was used, the milk (20 ml) and (NH 4 ) 2 S0 4 (4 g) being measured accurately. Care was taken to heat the filtrate at 100 °C for exactly 5 min before cooling it in ice-water. These precautions were taken in order to standardize the method for the measurement of the colour of the filtrate.

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A Colorimetric Method for the Estimation of Reducing Groups in Milk Powders

Cited by 30 publications

References 13 publications

Flavour defects in edible casein and skim-milk powder: I. The role of Maillard browning

Flavour defects in edible casein and skim-milk powder: I. The role of Maillard browning

Lipid autoxidation in freeze-dried meats

Certain non-biological properties of sterilized milk in relation to the treatment of the milk and the temperature of heating

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