Technological Parameters of Kefir Self-Pressing in Polyester Bags

Controlled whey separation, or syneresis, is a key technological task in the production of strained and concentrated fermented dairy products because it determines texture, water-holding capacity, and product yield. Kefir is a mixed-fermentation dairy product that requires gentle concentration by self-pressing. However, the effects of filtering fabric parameters and polyester bag design on process efficiency remain insufficiently studied. The aim of the work was to determine the most rational parameters of polyester bags for kefir self-pressing based on whey separation, total solids content, and sensory properties of the strained product. It featured kefir produced with kefir grains. At the first stage, the syneresis was evaluated in conical polyester bags with fabric densities of 110, 114, 125, 130, and 145 g/m2. The second stage focused on the 114 and 125 g/m2 samples. The amount of separated whey was determined gravimetrically. Other parameters included total solids content and sensory properties of strained kefir. Polyester fabric density was found to affect both the course of self-pressing and the properties of the final product. The 110 g/m2 fabric proved to be technologically unsuitable because kefir leaked through the pores. Based on the overall set of indicators, a conical bag made of 114 g/m2 polyester was identified as the most rational option. These findings can be applied to develop and improve technologies for strained and concentrated fermented dairy products with controlled texture and syneresis properties.