Durian (Durio zibethinus) is known as the king of fruits and is highly prized in Southeast Asia. Revered in the region for its unique flavour and taste, its overpowering and distinctive odour makes it less popular in the Western world.
A new study was conducted jointly by the National University of Singapore (NUS) and the NUS Suzhou Research institute to investigate the effects of sequential inoculation of the yeast Williopsis Saturnus var. saturnus NCYC22 (W. saturnus) on the viability of Bifidobacterium animalis subsp. lactis B94 and Lactobacillus casei L26, with durian pulp as the fermentable substrate.
They observed that the sequential inoculation of W. saturnus after B. animalis subsp. lactis did not result in any significant difference when compared with B. animalis subsp. lactis monoculture, as W. saturnus died soon after inoculation.
On the other hand, the sequential inoculation of W. saturnus was found to considerably improve the survival of L. casei, as well as to enhance the utilisation of glucose and fructose, when compared with L. casei monoculture.
Distinct durian odour
Furthermore, there were marked differences in the metabolism of organic acids, specifically in the case of lactic and succinic acids.
The researchers also noted the significantly increased levels of volatile compounds, such as alcohols (ethanol and 2-phenylethyl alcohol) and acetate esters (ethyl acetate, isoamyl acetate, and 2-phenylethyl acetate), which they wrote "would positively contribute to the flavour notes".
They added that despite the initial volatile sulphur compounds having been reduced to trace levels post-fermentation, the distinct durian odour remained.
This led them to state that using a combination of probiotics and W. saturnus to ferment durian pulp could result in a potential method of developing a "novel non-dairy durian-based functional beverage to deliver probiotics".
The researchers said the addition W. saturnus had no impact on Bifidobacteria or substrate transformation and metabolite formation because of Bifidobacteria’s low pH and high acetic acid production, which caused early death for the yeast.
They therefore concluded that "the use of a right combination of probiotics and W. saturnus could be a novel strategy for producing durian-based probiotic products".
Source: International Journal of Food Microbiology
"A novel non-dairy beverage from durian pulp fermented with selected probiotics and yeast"
Authors: Yuyun Lu, et al.