The effect of adding Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus on the acidity and overall consumer acceptability of Lebanese Kishk

Abstract

Kishk is a fermented cereal product made traditionally from bourghul (cracked wheat) and yogurt. Being a fermented product, which gets stored and used over a period of a year, moisture and acidity are two critical components of the preparation method and storage/spoilage. We investigated the effect of a pure Lactic acid bacteria (LAB) starter culture (Streptococcus thermophilus and Lactobacillus delbrueckii subsp. Bulgaricus) on the acidity and consumer acceptability of Lebanese Kishk. Traditional Lebanese Kishk was prepared and used as a control in this study. Three additional test samples were prepared by adding the following to bourghul; fresh cow milk "Milk", milk and LAB "Milk+LAB", and yogurt prepared by inoculating fresh cow milk with LAB. Samples containing yogurt exhibited higher acidity and lower moisture content during the preparation and fermentation phase, both of which are required parameters for safety. Even though the final product of all samples were comparable to the control in terms of moisture, the "Milk+LAB" sample was more acidic than the control. None of the tested samples had a significant impact on consumer overall acceptability of the final product; however, the "Yogurt+LAB" sample was significantly preferred over the control for its odor.