Evolution of lactic acid bacterial populations during lysine fortification of sourdough breads by addition of pistachio powder

Abstract

Food fortification is a current practise to increase the bioavailability of certain nutrients. In this study, 5% (w/w) pistachio powder was added to tender wheat flour or durum wheat semolina to evaluate its contribution to augment the amount of lysine in bread. Bread production was carried out by sourdough technology using a selected 3-species lactic acid bacterial (LAB) starter culture (Lactobacillus sanfranciscensis PON100336, Leuconostoc citreum PON10079 and Weissella cibaria PON10030). In order to determine the influence of pistachio powder on the evolution of LAB, sourdough bread productions were compared with control trials obtained from flour or semolina and evaluated for the development of the main microbial groups by plate counts. All sourdoughs were subjected to a long-time fermentation (21 h) and showed levels of LAB around 109 CFU/g, indicating the suitability of pistachio powder for lactic fermentation. Yeasts were also detected, in particular in semolina trials. MySeq Illumina technology was applied to investigate the bacterial composition of sourdoughs evidencing a different distribution of LAB species among the trials with Lactobacillus as being the major bacterial group in almost all sourdoughs, except that produced from flour supplemented with pistachio powder which displayed Weissella as dominant group. Physicochemical parameters were comparable among the trials. After baking, pistachio powder was found not to influence the height of the breads, but pistachio breads were more firm than control breads. Colour of the breads, as well as void fraction and cell density, were influenced by pistachio powder. The amount of lysine increased consistently thanks to pistachio supplementation which also determined a higher presence of o-xylene, p-cymene and limonene and the appearance of alpha-pinene and 1-octen-3-ol in the final breads. Sensory tests showed a higher appreciation of the judges towards the breads produced from flour and semolina supplemented with pistachio powder rather than control breads.