Lactulose content, colour and the organoleptic assessment of ultra heat treated and sterilized milks

Abstract

24 ultra heat treated (UHT) and 17 in-bottle sterilized milks prepared in commercial plants and of a similar age were presented to taste panels for assessment of flavour and colour. The colour was also analysed instrumentally and the lactulose content of the milks measured by an enzymic method. Flavour defects, other than the cooked flavour, were scored very low. The lactulose content of the milks was negatively correlated with the acceptability of the milks and positively correlated with the cooked flavour. Correlations were also found between the visual and instrumental assessments of milk colour and between some of the instrumental colour parameters and the lactulose content of the milks. UHT and in-container sterilized milks could not always be distinguished on the basis of their organoleptic qualities. The best distinction was observed in the scores for cooked smell and acceptability of taste. The usefulness of the lactulose content and/or the colour of the milks in discriminating between UHT and in-bottle sterilized milks was calculated. Using all the data, sterilized milk could be correctly identified in 96-7 % of decisions. The lactulose content of a milk was considered to give a good indication of the organoleptic quality of the milk.

Effect of orange fiber addition on yogurt color during fermentation and cold storage

“…2); therefore, fiber presented a darkening effect, probably due to the absorption of water by the fiber, as L* value of foods is associated to the amount of free water in the surface of a product more than the complete product. 26 This way, when fiber is added to the milk it is expected to absorb 11 g of water per gram of fiber, 27 therefore a decrease in whiteness is expected.…”

Kinetic Study on Color Changes in Milk Due to Heat

“…Starting from the work of Kessler and Fink (1986), this correlation has been investigated systematically using increasingly sensitive and reliable tristimulus calorimeters. Color data by means of such procedures may, for example, contribute to distinctions between sterilized and UHT milk (Andrews and Morant, 1987;Fink and Kessler, 1988). Activation energy of the browning reaction, according to Kessler and Fink (1986), was 116 KJ/mol.…”

Rapid determination of lactulose in milk by microdialysis and biosensors

“…Consequently, lactulose and undenaturted b-lactoglobulin concentrations have been proposed by some researchers, [2][3][4][5][6][7][8] and adopted by the International Dairy Federation (IDF) 9 and by the European Commission (EC), 10 as analytical indicators to distinguish UHT milk from in-container sterilised milk. For lactulose, an upper threshold value of 60 mg per 100 ml has been suggested in order to avoid excessive heat damage in UHT milk.…”