Selected chemical and microbiological characteristics of plain (n = 11) or sweetened (n = 11) natural stirred yoghurts collected in the Italian market were evaluated. A strong imbalance (1:103 to 1:105) between viable cell counts of Lactobacillus delbrueckii ssp. bulgaricus (LB) and Streptococcus thermophilus (ST) was observed in five sweetened samples. Unlike the plain samples, lactic acid content was higher than that of residual galactose, suggesting the possible involvement of either galactose or added sugar in microbial catabolism. Nevertheless, isotope ratio mass spectrometry of lactic acid and sugars isolated from two sweetened samples resulted in a similar 13C/12C ratio for lactic acid and lactose, thus suggesting the catabolism of this disaccharide only. A significantly (P < 0.001) lower level of galactose characterised sweetened yoghurts with respect to plain ones. This feature was not related to significant production of exopolysaccharides by yoghurt bacteria since these compounds were not detected in any of the analysed sweetened samples. Pectin or starch were detected in three sweetened yoghurts despite the fact that addition of thickener to the milk base is not permitted by Italian regulation. Levels of furosine ranged from 44 to 208 mg·100 g–1 protein, suggesting that milk for yoghurt manufacturing is sometimes over-heated. In this regard, evaluation of heat damage could be an additional parameter to characterise yoghurt quality.

Survey of selected chemical and microbiological characteristics of (plain or sweetened) natural yoghurts from the Italian market / I. De Noni, L. Pellegrino, F. Masotti. - In: LAIT. - ISSN 0023-7302. - 84:5(2004), pp. 421-433. [10.1051/lait:2004020]

Survey of selected chemical and microbiological characteristics of (plain or sweetened) natural yoghurts from the Italian market

I. De Noni
Primo
;
L. Pellegrino
Secondo
;
F. Masotti
Ultimo
2004

Abstract

Selected chemical and microbiological characteristics of plain (n = 11) or sweetened (n = 11) natural stirred yoghurts collected in the Italian market were evaluated. A strong imbalance (1:103 to 1:105) between viable cell counts of Lactobacillus delbrueckii ssp. bulgaricus (LB) and Streptococcus thermophilus (ST) was observed in five sweetened samples. Unlike the plain samples, lactic acid content was higher than that of residual galactose, suggesting the possible involvement of either galactose or added sugar in microbial catabolism. Nevertheless, isotope ratio mass spectrometry of lactic acid and sugars isolated from two sweetened samples resulted in a similar 13C/12C ratio for lactic acid and lactose, thus suggesting the catabolism of this disaccharide only. A significantly (P < 0.001) lower level of galactose characterised sweetened yoghurts with respect to plain ones. This feature was not related to significant production of exopolysaccharides by yoghurt bacteria since these compounds were not detected in any of the analysed sweetened samples. Pectin or starch were detected in three sweetened yoghurts despite the fact that addition of thickener to the milk base is not permitted by Italian regulation. Levels of furosine ranged from 44 to 208 mg·100 g–1 protein, suggesting that milk for yoghurt manufacturing is sometimes over-heated. In this regard, evaluation of heat damage could be an additional parameter to characterise yoghurt quality.
Heat damage; Isotope ratio mass spectrometry; Sweetened yoghurt; Thickener
Settore AGR/15 - Scienze e Tecnologie Alimentari
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2434/9465
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