Study of kefir and kefiran production

• Autor(a) principal: Anjos, Joshua Andre Margarido
• Data de Publicação: 2018
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10773/25643
• topic: Kefir; Kefir grains; Kefiran; Exopolysaccharide; Lactobacillus kefiranofaciens; Cheese whey

Kefir is a fermented milk beverage with unique sensory properties and high nutritional and therapeutic values. Currently, there is an increase in its consumption and manufacture in many countries, however, in Portugal, only recently this beverage has started to be produced industrially. Thus, a detailed study of kefir production should be done to help expanding the implementation of kefir industrial process in our country. Additionally, kefiran is a value-added exopolysaccharide (EPS) produced during kefir manufacture, mainly due to the presence of Lactobacillus kefiranofaciens in kefir grains, which could be of commercial interest, since it may have several food and medical applications. To produce kefiran, cheese whey, a by-product from dairy industry, which represents a significant environmental issue due to its high volumes produced and high organic matter content, could be used as a low-cost carbon source as it contains high amount of lactose. In this work, several fermentation conditions were studied for kefir production by kefir grains using UHT milk, and compared concerning pH values, lactose, lactic acid, and ethanol concentrations: initial kefir grains concentration (3, 6 and 9% (w/v)), initial milk volume (100 and 200 mL), agitation rate (0, 60 and 180 rpm) and temperature (controlled, 28 ºC, and room temperature, 21-25 ºC). The best conditions determined for kefir production were also assessed using a pasteurized cow milk sample provided by Lacto Serra company. The best conditions were achieved with 9% (w/v) of initial kefir grains concentration, 200 mL of initial milk volume, controlled temperature of 28 ºC and without agitation, allowing the production of this beverage in approximately 8 h, with both cow milk samples. Moreover, different culture media were tested and compared for kefiran production by kefir grains and by pure culture of Lactobacillus kefiranofaciens: MRS broth medium, UHT and pasteurized cow milk samples, cow cheese whey sample (concentrated and pasteurized) and sheep cheese whey sample (raw). In the end, kefiran extraction, purification and quantification was performed. Kefiran production was the highest when MRS broth medium was fermented by kefir grains during 96 h, resulting in a concentration of 1.69 g/L. Nevertheless, the best result using a cheese whey sample was obtained when cow cheese whey sample (concentrated and pasteurized) was fermented by pure culture of Lactobacillus kefiranofaciens during 148.5 h, providing 1.16 g/L of kefiran. This study showed that a low-cost carbon source like cheese whey can effectively be used to produce a value-added exopolysaccharide like kefiran. Although kefiran values seem promising, a lot of work can still be done concerning to kefiran production optimization.