Abstract

“Nostrano-cheeses” are traditional alpine cheeses made from raw cow's milk in Trentino-Alto Adige, Italy. This study identified lactic acid bacteria (LAB) developing during maturation of “Nostrano-cheeses” and evaluated their potential to produce γ-aminobutyric acid (GABA), an immunologically active compound and neurotransmitter. Cheese samples were collected on six cheese-making days, in three dairy factories located in different areas of Trentino and at different stages of cheese ripening (24 h, 15 days, and 1, 2, 3, 6, and 8 months). A total of 1,059 LAB isolates were screened using Random Amplified Polymorphic DNA-PCR (RAPD-PCR) and differentiated into 583 clusters. LAB strains from dominant clusters (n = 97) were genetically identified to species level by partial 16S rRNA gene sequencing. LAB species most frequently isolated were Lactobacillus paracasei, Streptococcus thermophilus, and Leuconostoc mesenteroides. The 97 dominant clusters were also characterized for their ability in producing GABA by high-performance liquid chromatography (HPLC). About 71% of the dominant bacteria clusters evolving during cheeses ripening were able to produce GABA. Most GABA producers were Lactobacillus paracasei but other GABA producing species included Lactococcus lactis, Lactobacillus plantarum, Lactobacillus rhamnosus, Pediococcus pentosaceus, and Streptococcus thermophilus. No Enterococcus faecalis or Sc. macedonicus isolates produced GABA. The isolate producing the highest amount of GABA (80.0±2.7 mg/kg) was a Sc. thermophilus.

Highlights

  • Traditional alpine raw milk cheeses are commonly produced in alpine regions including the province of Trentino in NorthEastern Italy

  • This study identified lactic acid bacteria (LAB) developing during maturation of “Nostrano-cheeses” and evaluated their potential to produce γ-aminobutyric acid (GABA), an immunologically active compound and neurotransmitter

  • The total bacterial counts were in the range of 8-9 log cfu/g from 24 h to 3 months of ripening and decreased after 6 and 8 months by 1 order of magnitude

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Summary

Introduction

Traditional alpine raw milk cheeses are commonly produced in alpine regions including the province of Trentino in NorthEastern Italy. They are called “Nostrano-cheeses” and are semicooked cheese made by mixing approximately in 1 : 1 ratio the raw cow’s milk from two different milking. The first milking is carried to dairy factory the evening before the cheese-making and is stored in large shallow tank for 9–11 hours where a spontaneous creaming occurs. After this overnight stage, the partially skimmed milk under the cream in the tank is manually drained from the cream fat and placed in the cheese-making vat. The ripening is held at about 18∘C for 3 to 8 months

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