Microbiological and Physichochemical Analysis of Milk Under Solar Powered Cooling System in Siaya County, Kenya

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Microbiological and Physichochemical Analysis of Milk Under Solar Powered Cooling System in Siaya County, Kenya

Maryanne Betsy Usagi, Benson Onyango, Bernard Muok and William Omuketi
Jaramogi Oginga Odinga University of Science and Technology, P.O BOX 210-40601 Bondo, Kenya
DOI: https://doi.org/10.51584/IJRIAS.2023.8613
Received: 01 June 2023; Revised: 01 June 2023; Accepted: 03 June 2023; Published: 07 July 2023

Abstract: – This study aimed to determine the effect of solar powered milk cooling on the microbiological and physicochemical properties of milk. So far, information on impact of solar milk cooling on the microbiological and physicochemical properties of milk remains limited. Samples of uncooled (144) and milk cooled (144) using SPMCS were analyzed for changes in physicochemical and bacterial counts. Clot on boiling, alcohol test and pH were determined as physical components of milk. Chemical composition such as butter fat content, lactose, protein and density were also determined using a lactoscan. Bacterial counts were determined and expressed as colony forming units (cfu). All cooled milk samples were negative for both COB and alcohol test while 12.5 % and 22.2 % of the uncooled milk samples were positive for COB and alcohol test respectively. The pH of cooled (6.63) and uncooled milk (6.4) was significantly different. Similarly, cfu for cooled (5.8 log10 cfu/ml) and uncooled milk (6.4 log10 cfu/ml) samples were significantly different. Negative clot on boiling and alcohol test for cooled milk indicates the effectiveness of SPMCS in preserving milk quality. Slightly higher pH and low bacterial counts of cooled milk was as a result of reduced microbial activity due to low temperatures provided by SPMCS. The system was effective in preserving milk quality on transit thereby lowering losses incurred by farmers.

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Key words: – Quality, Cooled, Uncooled, Solar, raw, milk

I. Introduction

Milk is a complex mixture of compounds, including water, fat, protein, lactose, enzymes, minerals, organic acids and vitamins (Kumar et al., 2018). It is a highly perishable food with a short shelf life of about 3–5 hours because it provides excellent nutrients that support the growth of microorganisms (Karmaker et al., 2020). The physicochemical conditions of unpreserved milk favour growth of yeasts, moulds and a broad spectrum of bacteria particularly at temperatures above 16 °C (De Marchi et al., 2014). These microorganisms alter the chemical composition of milk such as milk acidity thereby lowering its quality (Ghandi et al., 2020).
Milk quality refers to compositional characteristics that enhance the acceptability of milk and milk products, which include chemical, physical, technological, bacteriological and aesthetic characteristics (Kurwijila, 2016). It also encompasses milk safety which refers to the state whereby milk is safe for consumption. Consumption of safe milk is unlikely to cause harm to the consumer, or the risks associated with consumption are reduced to an acceptable level (Ndambi et al., 2018.).
Milk spoilage has been a major obstacle to the dairy sector in tropical countries. The high ambient temperature coupled with absence of cooling facilities accelerate the spoilage of milk produced (Wanjala et al., 2017). Poor upstream milk production practices cause milk spoilage and loss of farm earnings along the downstream dairy value chain (FAO, 2016). Milk contamination with microorganisms is a major concern since milk is normally transported to the market and collection centers at temperatures permissive for the growth of microorganisms (Gandhi, et al., 2020). In Kenya, lack of access to electrification by rural dairy farmers limits the deployment of technologies to enhance quality of milk (Foster et al., 2015). Absence of refrigeration facilities and low standards of hygiene by resource poor farmers result in milk with high bacterial count which negatively impacts the dairy product quality (Kurwijila, 2016). According to Paludetti et al. (2018), milk composition and microbiological load are important factors to consider when evaluating quality, due to their influence on milk processability, nutritional quality, dairy product quality and safety.