Chemical, Textural and Antioxidant Properties of Oat-Fermented Beverages with Different Starter Lactic Acid Bacteria and Pectin

Abstract

Currently, starter cultures for fermenting plant-based beverages are not widely available commercially, but producers can use starter cultures for dairy products. Therefore, the aim of this study was to determine the physicochemical, rheological, antioxidant and sensory properties of oat beverages with/without pectin fermented by four different dairy starter cultures. The use of a mono-starter with Lactobacillus bulgaricus or Sreptococcus thermophilus allows for the efficient use of glucose, and more lactic acid is accumulated. The beverage with L. bulgaricus is characterised by high adhesion, syneresis and low cohesiveness, and it has high antioxidant activity and a low sensory profile. Using starter with L. bulgaricus, S. thermophilus and some Lactococcus for fermentation yields a product with high sensory capacity, forming a high-viscosity beverage matrix with low syneresis, high water retention, chewy texture and stickiness. It has been observed that the absence of lactococci and the presence of Lactobacillus casei, L. Rhamnosus and L. paracasei in the starter yields a product with high antioxidant activity, especially in the presence of pectin. The use of pectin significantly improves the viscosity and textural properties of oat yoghurt, enhancing the drink's flavour and giving it body. For many reasons, the use of different commercial starters in the dairy industry results in different viscosities of oat fermented beverages, forming a matrix with different textural, sensory and antioxidant properties.

Keywords: antioxidants; fermentation; lactic acid bacteria; oat-based beverage; texture; viscosity.

Figure 1

The production steps of the fermented oat base.

Figure 2

Effect of starters and pectin on pH (A) and titratable acidity (B), absolute glucose concentration (C) and percentage of residual glucose (D). Blue bar—unfermented oat base without pectin, red bar—unfermented oat base with pectin, grey bar—oat-based fermented beverage without pectin, black bar—oat-based fermented beverage with pectin. The blue line shows the level of the index for the oat base without pectin and the red line shows the level of the index for the oat base with pectin. Asterisks indicate statistically significant differences between variants without pectin (control) and with pectin according to non-parametric one-way analysis of variance (Kruskal–Wallis) test, p < 0.05.

Figure 3

Effect of starter and the pectin to concentration on total phenol-containing compounds (TPCs) ((A), product; (B), protein-free extract). Blue bar—unfermented oat base without pectin; red bar—unfermented oat base with pectin; grey bar—oat-based fermented beverage without pectin; black bar—oat-based fermented beverage with pectin. The blue line shows the level of the index for the oat base without pectin and the red line shows the level of the index for the oat base with pectin. Asterisks indicate statistically significant differences between variants without pectin (control) and with pectin according to non-parametric one-way analysis of variance (Kruskal–Wallis) test, p < 0.05.

Figure 4

Total amount of extractable polysaccharides (EPSs). Blue bar—unfermented oat base without pectin; red bar—unfermented oat base with pectin; grey bar—oat-based fermented beverage without pectin; black bar—oat-based fermented beverage with pectin. The blue line shows the level of the index for the oat base without pectin and the red line shows the level of the index for the oat base with pectin. Asterisks indicate statistically significant differences between variants without pectin (control) and with pectin according to non-parametric one-way analysis of variance (Kruskal–Wallis) test, p < 0.05.

Figure 5

Sensory profile of oat-based fermented beverage. Controls without pectin (LB, ST, ProBio, Symb and oat base) are indicated by the thick solid lines, samples with pectin (LB + pectin, ST + pectin, ProBio + pectin, Symb + pectin and oat base + pectin) are indicated by the dashed lines.

Figure 6

Antioxidant activity of fermented oat base: Ferric-reducing antioxidant power (A); Radical-scavenging ability (B); OH free-radical-scavenging ability (C). Blue bar—unfermented oat base without pectin, red bar—unfermented oat base with pectin, grey bar—oat-based fermented beverage without pectin, black bar—oat-based fermented beverage with pectin. The blue line shows the level of the index for the oat base without pectin and the red line shows the level of the index for the oat base with pectin. Asterisks indicate statistically significant differences between variants without pectin (control) and with pectin according to non-parametric one-way analysis of variance (Kruskal–Wallis) test, p < 0.05.

Figure 7

Principal component analysis (A) of oat base and oat-based fermented beverages with/without pectin, dendrogram of oat-based fermented beverages with/without pectin (B) and heat-map correlation (C) of antioxidant activity and chemical composition.