Functional properties of water kefiran and its use as a hydrocolloid in baking

Abstract

Water kefir is produced by a microbial consortium, which is embedded into jelly crystals. These microbiota and the sparkling, sweet, slightly alcoholic drink have been in the focus of interest. This work showed that a food-grade, flour-like powder produced from the water kefir grains, which we termed water kefir powder (WKP), possesses promising hydrocolloid properties, which can be exploited in baking and beyond. For WKP production, grains were autoclaved, lyophilized and milled to a particle size below 0.025 mm. WKP was homogeneous, white- to cream-coloured and had a dry matter of 93.66 ± 0.07 %. It was not hygroscopic and could be stored in sealed plastic tins at room temperature. WKP aroma can be described as mainly sour, starchy, acetic acid-like and fermented. Aqueous solutions of WKP displayed a pH value of 3.8. Microscopic analysis of dry and wet WKP showed that it consisted of angular, sharp-edged particles whose angularity remained, but size increased during soaking. Furthermore, WKP became translucent when it was wet, whereby its water-holding capacity was not temperature dependent between room temperature (919 ± 0.39 %) and 75 °C (869 ± 0.41 %). Freezing experiments revealed a freeze–thaw stability of 95.0 ± 0.2 % for 8 % (w/v) WKP, 96.8 ± 0.4 % for 10 % (w/v) WKP and 98.8 ± 0.4 % for 12 % (w/v) WKP. Fat-binding capacity amounted 129 ± 0.22 %. No gel-building, emulsifying or foam-forming activity could be observed. Adding 1, 2 and 5 % WKP to wheat breads leads to decreased crumb firmness after 0 and 48 h and therefore increased freshness and retarded staling. No negative influence of WKP on smell and taste was found, whereas no potential for sodium reduction by using WKP could be found in this work.