Selecting Low Cost Freeze Dried Culture for Curd to Replace Existing Starter Culture
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Date
2013
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Uva Wellassa University of Sri Lanka
Abstract
Curd is a thick, sour, well known fermented milk product having close resemblance to yoghurt.
It has a distinct taste, richness and delicacy. It is not only refreshing and delicious but nutritious,
healthy and easily digestible. Curd is an integral part of Indian diet and possesses therapeutic
and dietetic properties (Gupta and Prasad, 2000). Curd is also known as probiotic or functional
food as it possesses live lactic acid bacteria. Benefits of consuming curd are; enhanced immune
response, balancing of fecal enzymes and intestinal micro flora, prevention of cancer, antibiotic
therapy, reduction of serum cholesterol and risk of coronary heart diseases, antagonism against
food borne pathogen, tooth decay organism and anti-tumor activity (Pattnaik and Mohapatra,
2000).
Bacterial cultures, known as starters are used in manufacturing of curd, yoghurt, kefir and other
cultured milk. The starter is added to the product and allowed to grow there under controlled
conditions. During fermentation, bacteria produce substances which give the cultured product
its characteristic properties such as acidity, flavour, aroma and consistency. Drop in pH, which
takes place when the bacteria fermenting lactose to lactic acid, has a preservative effect on the
product, while at the same time the nutritional value and digestibility are improved (Rubiga
Sivapatham, 2001).
Dairy starter cultures are carefully selected microorganisms, which are deliberately added to
milk to initiate and carry out desired fermentation under controlled conditions. Most of them
belong to lactic acid bacteria (Lactococcus, Lactobacillus, Streptococcus and Leuconostocs).The
different starter used in the manufacture of curd includes Lactococcus. lactis, L. cremoris,
Streptococcus thermophilus, Lactobacillus bulgaricus, L. plantarum and lactose fermenting
yeasts. The main objective of this study was to select a most cost optimized starter culture to
replace the existing composite starter cultures, without changing its organoleptic properties.
Methodology
Curds were prepared according to the standard procedure (SLS part 2:1989). Two starter
cultures were used (A and B) which were lower in cost than the existing starter culture.
Organoleptic characteristics of curds prepared with A and B were compared with the curd
thermophilus,
Lactobacillus delbrueckii subsp. Bulgaricus and Bifidobacterium species and culture type “B”
and
Streptococus lactis subsp. lactis biova diacetylactis. Completely Randomized Design (CRD)
comprising three treatments with four replicates was used as the experimental design.
Parametric data analysis was done using ANOVA for significance under α = 0.05 level using
MINITAB 15 statistical software package. Non parametric data analysis was done by Friedman
non-parametric test using MINITAB 15 statistical software package. The sensory evaluation
was carried out with seven trained panelists and 23 untrained panelists using nine point hedonic
scale to assess sensory attributes of appearance, flavour, texture, mouth feel and overall
acceptability.
Shelf life of the curd prepared was determined by analyzing titratable acidity, pH, yeasts and
moulds, coliforms at five days intervals for 35 days and compared with the control.
Results and Discussion
According to the figure 1 there was no significant difference between sensory attributes of
appearance, flavour, texture, mouth feel and overall acceptability of “A”, “B” with the control
(P>0.05). However, curd prepared with culture type “A” was rejected due to prolong setting
time compared to control. Culture type “B” was selected as the most cost optimized starter
culture which gives similar properties and used for further analysis.
Description
Keywords
Animal Sciences, Animal Production Technology, Milk Production, Milk