Monitoring Commercial Starter Culture Development in Presence of Red Grape Pomace Powder to Produce Polyphenol-Enriched Fresh Ovine Cheeses at Industrial Scale Level

Abstract

Red grape Nero d’Avola cultivar grape pomace powder (GPP) was applied during fresh ovine cheese production in order to increase polyphenol content. Before cheeses were produced, the bacteria of a freeze-dried commercial starter culture were isolated and tested in vitro against GPP. Two dominant strains, both resistant to GPP, were identified. Thestarter culture was inoculated in pasteurized ewe’s milk and the curd was divided into two bulks, one added with 1% (w/w) GPP and another one GPP-free. GPP did not influence the starter culture development, since lactic acid bacteria (LAB) counts were 109 CFU/g in both cheeses at 30 d. To exclude the interference of indigenous LAB, the pasteurized milk was analyzed, and several colonies of presumptive LAB were isolated, purified and typed. Four strains were allotted into Enterococcus and Lacticaseibacillus genera. The direct comparison of the polymorphic profiles of cheese bacteria evidenced the dominance of the starter culture over milk LAB. The addition of GPP increased cheese total phenolic compounds by 0.42 g GAE/kg. Sensory evaluation indicated that GPP-enriched cheese was well appreciated by the judges, providing evidence that GPP is a suitable substrate to increase the availability of total phenolic content in fresh ovine cheese.

Effect of grape pomace from red cultivar 'Nero d’Avola' on the microbiological, physicochemical, phenolic profile and sensory aspects of ovine Vastedda-like stretched cheese

“…Bacteria and yeast were below the detection limits most likely due to the oven-drying treatment performed on grape pomace (Mainente et al, 2019). The absence of microorganisms at detectable levels in Nero d'Avola cultivar GPP was already shown by Gaglio, Barbaccia, et al (2021), Gaglio, Restivo, et al (2021) and Barbaccia et al (2021) for the vintage 2018, 2019 and 2020.…”

“…Cheesemaking was performed at an industrial level in the dairy factory 'Biopek' located at Gibellina following the protocol of production for the stretched cheese 'Vastedda' as reported by Gaglio, Restivo, et al (2021). Two cheese trials were obtained with the starter culture: CTR, control cheese produced from pasteurized ewe's milk; EXP, experimental cheese produced from pasteurized ewe's milk and 1% (w w −1 of curd) GPP, based on the previous studies by Barbaccia et al (2021), Gaglio, Barbaccia, et al (2021) and Gaglio, Restivo, et al (2021). Each trial was carried out in a stainless steel vat containing 500 L of milk.…”

Development of “Quadrello di Ovino”, a Novel Fresh Ewe’s Cheese

“…All undesired bacteria ( Pseudomonas , members of Enterobacteriaceae family, L. monocytogenes , Salmonella spp., E. coli and CPS) were undetectable. Barbaccia et al [ 45 ] reported similar findings for pasteurized ewes’ milk used for another fresh ewe’s milk cheese production, Pecorino “Primosale”. After inoculation, starter cultures were monitored during cheese making.…”

“…These results might be ascribable to the ability of the indigenous milk bacteria to survive during the pasteurization process [ 41 , 42 ], but also to a post-pasteurization contamination [ 43 , 44 ]. Furthermore, this phenomenon seems to be common in pasteurized ewe’s milk [ 8 , 16 , 45 ]. All undesired bacteria ( Pseudomonas , members of Enterobacteriaceae family, L. monocytogenes , Salmonella spp., E. coli and CPS) were undetectable.…”

Polyphasic Characterization of Microbiota of “Mastredda”, a Traditional Wooden Tool Used during the Production of PDO Provola dei Nebrodi Cheese

“…All isolates were purified by several streaking steps onto the same agar media used for plate count and tested for Gram type by treatment with 3% (w/v) KOH method [32], and for catalase test performed by the addition of H 2 O 2 at 3% (v/v) to the colonies [33]. Pure cultures were first subjected to a grouping based on cell morphology and arrangement of the cells [34], and then analysed for their physiological and biochemical traits as described by Gaglio et al [35]. LAB cocci were further analysed for their growth at pH 9.2 and in the presence of NaCl (6.5 g/L) to discriminate enterococci from other dairy LAB cocci.…”