Abstract
The physicochemical and sensory properties of five commercially available sour milk (amasi) products- AoA, AoB, AoC, AoD and AoE were analyzed in 3 batches. Samples were collected from retail shops in Thohoyandou. The products were examined forEscherichia coli, lactic acid bacteria (LAB), total plate count (TPC), pH, titratable acidity (TA), colour, viscosity and sensory properties. Microbial analysis results for LAB ranged between 1.25 × 105 and 1.97 × 106cfu with sample AoA and AoB being the highest by 1.96 × 106 and 1.97 × 106 cfu, respectively. E. coli count ranged from 1.22 × 104 to 1.78×105 cfu with sample AoE and AoC being the lowest and highest (p < 0.05), respectively. TPC had the least number of counts with the values between 4.2 × 103 and 9.1 × 104 cfu. The pH values of the products ranged between 4.22 and 4.34 and TA ranged between 0.80 and 0.84. Colour measurements gave L* values of the products ranging from 33.77 to 40.19, while a* and b* values were 3.08 to 6.43 and 13.17 to 18.77, respectively. Differences existed in viscosities of the products that were not significantly different (p < 0.05). Sensory score for the overall acceptability indicated that consumers did like the sour milk, as the values ranged from 3.8 to 4.4. Although there were significant differences (p < 0.05) in terms of sweetness, smoothness and astringency, they did not affect the consumer acceptability of the products. Presence of E. coli in the sour milk products can be of health concern to consumers. Key words: Sour milk, amasi, physicochemical, microbial.
Highlights
Sour milk known as amasi among the Zulus in South Africa is a fermented product produced in clay pots and gourds which are used repeatedly through spontaneous fermentation of raw milk that occurs naturally at ambient temperature of ยฑ 5ยฐC (Bryant, 1949; Keller and Jordan 1990; Gadaga et al, 2001)
Samples (1 mL) of each sour milk were serially diluted (10-1, 10-2, 10-3 and 10-4) in 9 mL of buffered peptone water (BPW) and appropriate dilution was surface plated onto Sorbitol MacConkey agar (SMAC) (Oxoid) for E. coil and de Man Rogosa and Sharp (MRS) agar was prepared from the ingredients for Lactobacillus
The outcome of this study showed the availability of E. coli in the sour milk products which can be of health concern to consumers
Summary
Sour milk known as amasi among the Zulus in South Africa is a fermented product produced in clay pots and gourds which are used repeatedly through spontaneous fermentation of raw milk that occurs naturally at ambient temperature of ยฑ 5ยฐC (Bryant, 1949; Keller and Jordan 1990; Gadaga et al, 2001). Attribute Sourness Sweetness Texture (thickness) Smoothness Astringency Colour Overall acceptability. Examples of amasi products in the study location include Limpopo dairy maas, Clover Inkomazi, Save Moramasi/ Spar maas, Moordriftmaas and Hygienik (amaziakgomo). Sour milk is one of the products in which microorganisms are used during its production; in cases where hygienic practices are not properly applied, microbial contamination may occur during processing, distribution of product and retail outlets. Monitoring the quality of dairy product is important, considering the safety of the consumers. Since milk and milk products are good vehicles for both beneficial and harmful microorganisms, some of which may have health and subsequent financial consequences to the consumer, it is important to independently monitor quality. This study, examined those physical, chemical, microbial and sensory parameters that determine quality of sour milk product
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