Development, optimization and integrated characterization of rice-based yogurt alternatives enriched with roasted and non-roasted sprouted barley flour

Abstract

Plant-based yogurt substitutes ("gurts"), whose market growth is steadily increasing, have emerged as a promising option to promote more sustainable diets and food systems, especially when produced with locally sourced or low-input crops like barley. In this study, a novel gurt made with rice (10 %) and sprouted barley (5 %), was designed. Four lactic acid bacteria strains, Levilactobacillus brevis AM7, Leuconostoc pseudomesenteroides DSM20193, Lactiplantibacillus plantarum 18S9 and H64, were used as starters for making prototypes. Although with some differences in their acidification kinetics and proteolysis, all the strains adapted to the matrix. Then the formulation and production process were optimized. The use of sprouted barley, compared to raw flours, provided a content of amino acids 9-fold higher, further increased (up to 35 %) by the fermentation, and a more complex aroma profile characterized by the presence of furans and aldehydes. However, the high amylolytic activity in sprouted barley interfered with starch gelatinization decreasing the viscosity of the products from 3.3 to 0.08 Pa∗s. To overcome this challenge and obtain a creamy and spoonable product, sprouted barley flour was roasted, deactivating the enzymes and conferring a nutty and toasted flavor to the gurts due to the presence of pyrazines. The stability of the key biochemical and microbiological parameters during refrigerated storage was also assessed. Hence, plant-based gurts made with sprouted barley, emerge as a sustainable and health-promoting substitute to traditional dairy yogurts.

Keywords: Fermentation; GABA; Germination; Sprouted barley; Viscosity; Yogurt alternatives.

Graphical abstract

Fig. 1

Acidification kinetics parameters of the gurts containing rice and sprouted barley flours, fermented with L. platarum 18S9 (18S9), L. brevis AM7 (AM7), L. plantarum H64 (H64), and Leuc. mesenteroides DSM20193 (DSM20193). A, ΔpH between the initial value of pH and that reached at the stationary phase; V_max, maximum rate of acidification expressed as ΔpH/h; λ, length of the adaptation phase measured in hours. The data are the means of three independent experiments ± standard deviation. ^a-cValues with different superscript letters differ significantly (P < 0.05).

Fig. 2

Acidification kinetics parameters of the barley-based gurts. rB-G and sB-G, not fermented controls respectively produced with raw or sprouted barley flours and chemically acidified with lactic acid; fB-G and sfB-G, gurts respectively produced with raw or sprouted barley flours and fermented with L. plantarum H64; sfRB-G, fermented gurt produced with roasted sprouted barley. A, ΔpH between the initial value of pH and that reached at the stationary phase; V_max, maximum rate of acidification expressed as ΔpH/h; λ, length of the adaptation phase measured in hours. The data are the means of three independent experiments ± standard deviation. ^a-cValues with different superscript letters differ significantly (P < 0.05).

Fig. 3

Free amino acids concentration (mg/kg) of the barley-based gurts. rB-G and sB-G, not fermented controls respectively produced with raw or sprouted barley flours and chemically acidified with lactic acid; fB-G and sfB-G, gurts respectively produced with raw or sprouted barley flours and fermented with L. plantarum H64; sfRB-G, fermented gurt produced with roasted sprouted barley. The data are the means of three independent experiments ± standard deviation. ^a-eValues with different superscript letters, within the same amino acid, differ significantly (P < 0.05).

Fig. 4

Principal component analysis based on the Volatile Organic Compounds profile of the barley-based gurts. rB-G and sB-G, not fermented controls respectively produced with raw or sprouted barley flours and chemically acidified with lactic acid; fB-G and sfB-G, gurts respectively produced with raw or sprouted barley flours and fermented with L. plantarum H64; sfRB-G, fermented gurt produced with roasted sprouted barley.

Fig. 5

Viscosity, expressed as mPa∗s, of the gurts before (t0) and after (tf) fermentation and after 7 (t7), 14 (t14), and 30 (t30) days of refrigerated storage. rB-G and sB-G, not fermented controls respectively produced with raw or sprouted barley flours and chemically acidified with lactic acid; fB-G and sfB-G, gurts respectively produced with raw or sprouted barley flours and fermented with L. plantarum H64; sfRB-G, fermented gurt produced with roasted sprouted barley. The data are the means of three independent experiments ± standard deviation. Different uppercase letters between different incubation time of the same sample mean significant differences at a P < 0.05. Different lowercase letters among different samples within the same time of incubation mean significant differences at a P < 0.05.

Fig. 6

Sensory analysis of analysis of the barley-based gurts. rB-G and sB-G, not fermented controls respectively produced with raw or sprouted barley flours and chemically acidified with lactic acid; fB-G and sfB-G, gurts respectively produced with raw or sprouted barley flours and fermented with L. plantarum H64; sfRB-G, fermented gurt produced with roasted sprouted barley.