Biofilm and microstructure of small ruminant skin used in making traditional dairy products

Background

Bouhezza is a traditional Algerian cheese that is ripened in permeable goatskin bags known as Djeld, which enable spontaneous coagulation, drainage and maturation. Despite their central role in traditional Bouhezza production, the functional mechanisms of goatskin containers are poorly understood.

Aims

This study aimed to elucidate the microstructural and microbial dynamics of goatskin used in Bouhezza cheese production, with a focus on its potential role as a semipermeable membrane and microbial reservoir.

Methods

Goatskin samples were analysed before and after drying and Lben (fermented milk) treatment using scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM). Porosity, pore area and microbial colonisation patterns were assessed.

Major Findings

Drying significantly increased skin porosity from 5% (mean pore area: 3026 μm²) in fresh skin to 11% (mean pore area: 4250 μm²). After contact with Lben, porosity decreased to 4% in both fresh and dried skins, with mean pore areas reduced to 2703 and 3377 μm², respectively, reflecting microbial adhesion and biofilm formation. High-resolution SEM and CLSM imaging revealed filamentous Lben structures entrapping casein and microbial cells, likely regulating moisture and air exchange during cheese maturation. Moreover, Lben contact enriched the goatskin biofilm with lactic acid bacteria and yeasts, promoting the development of unique cheese texture, flavour and biochemical profiles. These microstructural and microbial ecosystems were associated with intensified lipolysis and flavour development in skin-aged cheeses.

Scientific and industrial implications

This study demonstrated that goatskin bags serve a dual function in Bouhezza cheese production: acting both as a semipermeable maturation membrane and as a dynamic microbial ecosystem that shapes the traditional character of Bouhezza cheese. These findings offer mechanistic insights into traditional cheese maturation and support the valorisation and preservation of artisanal dairy practices. Further research on the metabolic activity of biofilms in such systems is required.