Abstract
The reformulation of dairy products to contain less added sugar can contribute to reducing sugar consumption, thereby reducing the risk of non-communicable diseases. The objective of this study was to investigate the microbial ecology of reformulated yoghurt, which was produced using bi-enzymatic modification of lactose to increase its sweetness by a factor of 2–3. Ultimately, this reformulation strategy could reduce the amount of added sugar needed for equal sweetness of the end product. The bi-enzymatic modification relied on utilisation of a β-galactosidase enzyme to convert the milk sugar lactose to galactose and glucose, followed by the enzymatic conversion of the glucose moiety to fructose using a glucose isomerase. The microbial ecology of reformulated yoghurt produced with two mixed starter culture preparations containing either Streptococcus (S.) thermophilus and Lactobacillus (Lb.) delbrueckii or S. thermophilus, Lb. acidophilus and Bifidobacterium sp. strains, was analysed during fermentation and cool storage using 16S rRNA based metagenomics. None of the yoghurt samples showed a significant difference in microbial composition between sweetness-enhanced and regular milk at all sampling time points during manufacture and storage of yoghurt. However, a significant difference between the microbiota of inoculated milk before and after fermentation was observed. In both types of yoghurt, the starter culture genera dominated the microbial ecology at the end of fermentation as expected, reducing the possibility of growth of potentially pathogenic or spoilage bacteria possibly resulting from a changed carbohydrate spectrum.
Highlights
Sugar is vital for the healthy functioning of the human body, yet its excess consumption should be minimised in order to reduce the risk of non-communicable diseases such as diabetes mellitus type II
Statistical analysis of samples taken during fermentation and post-acidification storage demonstrated that there was no significant difference between the microbial composition of yoghurt produced with either sweetness-enhanced or regular milk
Sweetness-enhanced yoghurt samples taken during fermentation and post-acidification storage were analysed using 16S rRNA gene sequencing and statistical analyses demonstrated no significant difference between the microbial composition of this yoghurt compared to regular yoghurt
Summary
Sugar is vital for the healthy functioning of the human body, yet its excess consumption should be minimised in order to reduce the risk of non-communicable diseases such as diabetes mellitus type II. In Germany, dairy products contribute to the daily added sugar consumption by 7–9% (Alexy et al 2003; Max Rubner-Institut 2008; Max Rubner-Institut 2016). The reformulation of fermented dairy products to contain less added sugar can contribute to reducing sugar intake in the population. The natural milk sugar lactose is present in these products at about 4–6%, this sugar is not perceived as sweet (Chandan 2006). One approach to reformulate sweetened dairy products is to increase the sweetening power of lactose by converting this disaccharide into its sweeter monosaccharide components using a β-galactosidase enzyme to yield galactose and glucose (Harju et al 2012). As the individual monosaccharide components are sweeter than lactose, the overall sweetness of lactose can be increased by a factor of 2–3
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