Some aspects of the production and quality improvement of fermented milk/cereal mixture (kishk)

Khaskheli, Muhammad (1998) Some aspects of the production and quality improvement of fermented milk/cereal mixture (kishk). PhD thesis, University of Glasgow.

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Kishk is a very popular dried fermented milk/cereal mixture consumed in many countries of the world. The manufacture of Kishk is based on traditional methods, and may differ from one region to another. In the present study, the following aspects were investigated: First, standardising the production of laboratory-made Kishk; after using different ratios of wheat Burghol and yoghurt, a ratio of 1:4 was found to be suitable. Second, evaluating the compositional quality of Burghol made from different varieties of oats and barley, and the effect of these cereals on the overall characteristics of Kishk. Third, assessing the quality of Kishk using different cereals (porridge oats, oats flour, wheat flour, Burghol and Burghol flour), yoghurt, acidulant and/or 'milk'. Burghols from different varieties of barley and oats were prepared in a similar manner to that for the production of wheat Burghol. The traditional cracking process was successful for barley and oats, but difficulties were experienced in the separation of husk from the oats product. The chemical composition of the parboiled 'cracked' cereals were compared with that of the original grains, and with wheat Burghol. In all, the proximate composition (i.e. fat, protein and ash) of the parboiled 'cracked' products were reduced compared to the original cereals. Sensory evaluation of these Kishks could be summarised as follows: First, Kishks made with different cereal Burghols (oats, barley or wheat) were differentiated by the type of cereal used. Second, the flavour of Kishk made with different cereals (oats and wheat), yoghurt, GDL and 'milk' were different. Most of the odour, flavour, after-taste and mouth feel characters have differentiated the Kishk according to the type of 'dairy' base used. The perceived mouth feel characters (chalky, sticky, slimy) differentiated the Kishk according to the type and particle size of cereals (e.g. porridge oats, oats flour, wheat Burghol or wheat flour) used. Third, Kishk made with different wheat products (Burghol, Burghol flour or wheat flour) was also differentiated by the particle size. Fourth, wheat flour-based Kishk was perceived to have better mouth feel characters followed by Burghol flour- and Burghol-based Kishk. Yoghurt/Burghol or wheat flour mixtures were studied during the secondary fermentation period (0, 48, 96 and 144 h), and the influence of particle size of the cereal was evident on the β-amylase and proteolytic activities. Burghol-based mixture had the highest β-amylase content/activity and wheat flour the lowest, whilst the non-protein nitrogen compounds content was higher in wheat flour than the Burghol-based mixture after 144 h. The degradation of starch in all these mixtures was almost linear during the secondary fermentation period. This appeared to be influenced by the interactions between the starch and other components such as protein, lipids and polyphenols to make the starch resistant to enzymatic degradation. The release of enzyme inhibitors such as phytic acids during the secondary fermentation period may also have interfered in the recovery of the starch during analysis. The microstructure of cereal (Burghol or wheat flour)/yoghurt or whey from yoghurt mixture suggest that physical change in starch granules occurred rather than degradation.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Subjects: S Agriculture > S Agriculture (General)
Colleges/Schools: College of Medical Veterinary and Life Sciences
Supervisor's Name: supervisor, Not known
Date of Award: 1998
Depositing User: Mrs Monika Milewska-Fiertek
Unique ID: glathesis:1998-38917
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 09 Nov 2018 11:57
Last Modified: 17 Oct 2022 16:12
Thesis DOI: 10.5525/gla.thesis.38917
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