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. 2023 Sep 15;12(18):3454.
doi: 10.3390/foods12183454.

A Thorough Investigation of the Microbiological, Physicochemical, and Sensory Properties of Ewe's Yoghurt Fermented by a Selected Multi-Strain Starter Culture

Giuliana Garofalo  1 , Marialetizia Ponte  1 , Gabriele Busetta  1 , Marco Tolone  1 , Adriana Bonanno  1 , Baldassare Portolano  1 , Raimondo Gaglio  1 , Hüseyin Erten  2 , Maria Teresa Sardina  1 , Luca Settanni  1
Affiliations

A Thorough Investigation of the Microbiological, Physicochemical, and Sensory Properties of Ewe's Yoghurt Fermented by a Selected Multi-Strain Starter Culture

Giuliana Garofalo et al. Foods. .

Abstract

This work was carried out with the aim to investigate the microbiological, physicochemical, and sensory properties of an innovative yoghurt produced from ewe's milk. Experimental yoghurt productions were performed with a commercial freeze-dried starter preparation and a natural milk starter culture (NMSC) of Streptococcus thermophilus and Lactobacillus delbrueckii. The two yoghurts did not differ for colour parameters, showing an average value of lightness, redness, and yellowness of 94.99, -3.74, and 9.37, respectively. The yoghurt produced using the NMSC as a fermenting agent was characterised by a significantly lower fat percentage and a higher antioxidant potential than commercial starters. Microbiological analysis confirmed the safety of the final product and a level of living lactic acid bacteria of 108 CFU/g. Sensory analysis revealed some differences among yoghurts regarding unpleasant odour, homogeneity, and persistence in the mouth, but the yoghurt processed with NMSC was more appreciated. Thus, the production of ewe's yoghurt fermented by a selected multi-strain starter culture represents an interesting strategy to enlarge the functional ovine dairy product portfolio.

Keywords: antioxidant capacity; ewe’s yoghurt; lactic acid bacteria; milk starter culture; sensory traits.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Flow chart of ewe’s yoghurt.
Figure 2
Figure 2
Microbiological loads of milk samples before pasteurization. Results indicate mean values and SD of four determinations (carried out in duplicate for two independent productions). Abbreviations: EY-1, production performed with freeze-dried commercial starter culture (starter formulation YODOX91); EY-2, production performed with a multi-strain milk starter culture consisting of S. thermophilus and L. delbrueckii; RM, raw milk; TMM, total mesophilic microorganisms; E., Escherichia; LAB, lactic acid bacteria; MR, mesophilic rod; TR, thermophilic rod; MC, mesophilic cocci; TC, thermophilic cocci.
Figure 3
Figure 3
Growth of starter cultures during yoghurt production. Units are log CFU/mL for liquid samples and log CFU/g for solid samples. Results indicate mean values ±SD of four plate counts (carried out in duplicate for two independent productions). a, b, c = p < 0.05. Abbreviations: TMM, total mesophilic microorganisms; S., Streptococcus; L., Lactobacillus; PM, pasteurised milk; IM, inoculated milk; Y, yoghurt; EY-1, production of ewe’s yoghurt performed with freeze-dried commercial starter culture (starter formulation YODOX91); EY-2, production of ewe’s yoghurt performed with a multi-strain milk starter culture consisting of S. thermophilus and L. delbrueckii.
Figure 4
Figure 4
Spider diagram of sensory evaluation of yoghurts. Abbreviations: CCY, commercial cow’s yoghurt; EY-1, production of ewe’s yoghurt performed with freeze-dried commercial starter culture (starter formulation YODOX91); EY-2, production of ewe’s yoghurt performed with a multi-strain milk starter culture consisting of S. thermophilus and L. delbrueckii; ** p < 0.01; *** p < 0.001; n.s., not significant (p > 0.05).
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