Writing in Applied Microbiology, the team from the National University of the Littoral in Argentina investigated the functional potential of postbiotic compounds made from pH-controlled fermentation of milk, at laboratory and industrial scale.
Proteolytic activity and antibody secretion
Results in the mice study showed proteolytic activity (PA) of the fermented milk postbiotics was higher than that of other commercial cultures and Lactobacillus strains. Results also showed mice fed the postbiotics secreted higher amounts of IgA or immunoglobulin – a crucial antibody and the most abundant defence in the mucosa-associated immune system. This higher secretion, the researchers said, led to a “significantly higher” survival against Salmonella infection.
“In the present study, it was demonstrated that the pH-controlled milk fermentation using the proteolytic DSM-100H culture could be a suitable strategy to obtain a cell-free supernatant with immunomodulatory and protective capacity against Salmonella infection in mice,” the researchers wrote.
At a time when health promotion and disease prevention were increasing in interest, they said the postbiotics were promising for functional food development.
“These postbiotics may be an attractive alternative as ingredients to produce functional foods, especially when the characteristics of the food matrix are not favorable to host viable cells of probiotic micro-organisms.”
Previous work, they added, demonstrated butter milk was a “suitable substrate” for the fermentation process.
Beyond probiotics, beyond dairy...
The researchers said fermented dairy products carrying probiotic bacteria were “functional food market leaders” that aligned with a growing desire for health promotion and disease prevention. But, certain characteristics of probiotics – including sensitivity to lactic acid or osmotic pressure and the need for low-temperature storage – meant these ingredients were largely confined to dairy products.
Use of bioactive peptides from milk proteins, like postbiotics, therefore presented “technological advantages”, the researchers said, such as a longer shelf-life, easier storage, handling, transportation and reduced refrigeration time.
Importantly, the postbiotics developed in this study, they said, were effective when produced at both laboratory and industrial level.
“These results suggest that the production at different scales and the spray drying process would not interfere with the protective effect,” the researchers wrote.
Spray drying also enabled nutritional and sensorial qualities to be retained, together with an extreme reduction in weight for transportation and an extended shelf-life, they added.
In vivo trials
The researchers used 81 six-week-old male mice, split into experimental groups of seven, 10 or 15, to test the postbiotics. Secretory IgA was quantified by looking at the content in faeces, and Salmonella survival tested by introducing a single infective dose to the mice and monitored daily for 20 days.
Source: Applied Microbiology
Published ahead of print, doi: 10.1111/jam.14276
Title: “Postbiotics produced at laboratory and industrial level as potential functional food ingredients with the capacity to protect mice against Salmonella infection”
Authors: E. Dunand et al.