Abstract
Food spoilage is a complex process and excessive amounts of foods are lost due to microbial spoilage even with modern day preservation techniques. The aim of this study was to assess the microbiological quality of some dairy products in Beni-suef city, Egypt. A total of 210 samples of some dairy products (Kareish, Tallaga, Ras cheeses, small scale and large scale yoghurt, small scale and large scale cream samples) (30 of each) were collected from local retail stores, dairy shops and farmers' markets in Beni-Suef city. All samples were analysed for total bacterial count (TBC), total coliforms count, total yeast and mold count, total psychrotrophic count, lipolytic count and proteolytic count. The mean value of Kareish cheese and small scale cream for TBC were 1.07×107 ± 5.64 ×106 and 3.35×106 ± 1.23×106cfu/g, respectively. The mean values of Kareish, Tallaga, Ras cheeses, small scale yoghurt and small scale cream for total coliforms count were 2.55×105 ±1.59×105, 9.58×102 ± 4.32×102, 88.10 ± 21.11, 1.94×102 ± 79.47 and 1.58×104 ± 5.85×103cfu/g, respectively. The mean values for total yeast and mold count were 1.83×105 ± 9.25×104, 6.10×102 ± 3.35×102, 54.67 ± 22.04, 2.66×105 ± 8.07×104 and 2.57×104 ± 2.10×104cfu/g, respectively. The mean values for total psychrotrophic count were 2.89×107 ± 1.36×107, 1.16×106 ± 7.00×105, 2.46×106 ± 4.50×105, 7.81×105 ± 3.37×105 and 2.51×106 ± 6.95×105cfu/g, respectively. The mean values for lipolytic count were 1.23×106 ± 5.18×105, 9.32×105 ± 5.63×105, 2.91×106 ± 4.13×105, 2.32×105 ± 8.68×104 and 3.00×106 ± 7.34×105cfu/g, respectively. The mean value for proteolytic count were 1.16×106 ± 4.88×105, 9.94×105 ± 6.03×105, 5.85×106 ± 7.58×105, 3.32×105 ± 2.12×105 and 5.21×106 ± 1.27×106cfu/g, respectively. In conclusion, the presence of these organisms indicated that the examined dairy products were of inferior quality which reflects unhygienic measures, inadequate heat treatment during the manufacture, using bad quality ingredients or additives and improper sanitation during handling, storage and distribution.
Highlights
Milk and dairy products such as cheese are rich in nutrients such as protein, calcium, vitamins, phosphorus, magnesium, zinc, etc. providing a major part of human food, due to high nutritive value of these products, they provide a good media for the growth and multiplication of many of microorganisms (Ledenbach and Marshall, 2009; Pal and Awel, 2014)
Yeasts are the most important contaminants in some types of dairy products. This is especially relevant in fermented products such as yoghurt and sour milk, where yeast species are the major cause of spoilage because the low pH provides a suitable environment for their growth (Rohm et al, 1992)
The results given in Table (1) showed that the mean values of microbial load of the examined Kareish cheese samples were 1.07× 107 ± 5.64 × 106, 2.55×105 ± 1.59×105, 1.83×105 ± 9.25×104, 2.88×107 ± 1.36×107, 1.23×106 ± 5.18×105, 1.16×106 ± 4.88×105 cfu / g for total bacterial count (TBC), total coliforms count, total yeast and mold count, total psychrotrophic count, lipolytic count and proteolytic count, respectively
Summary
Milk and dairy products such as cheese are rich in nutrients such as protein, calcium, vitamins, phosphorus, magnesium, zinc, etc. providing a major part of human food, due to high nutritive value of these products, they provide a good media for the growth and multiplication of many of microorganisms (Ledenbach and Marshall, 2009; Pal and Awel, 2014).Cheese is essentially a microbial fermentation of milk by selected lactic acid bacteria whose major function is to produce lactic acid from lactose causing curd formation, the poor hygienic conditions during milking and cheese making and the inappropriate conditions of their storage negatively influenced the cheese quality (Özdemir et al, 2010). Yoghurt is one of the most popular fermented dairy products which have a wide acceptance worldwide that obtained by controlled fermentation of milk by lactic acid bacteria, which is carried out by Lactobacillus bulgaricus and Streptococcus thermophiles (Tamime and Robisons, 2007). It is considered a nutrient dense food, whereas it's highly nutritious, digestible and a source of more than ten essential nutrients, certain minerals and vitamins (Weerathilake et al, 2014). The changes in the physical, chemical and microbiological structures of yoghurt determine the storage and shelf life of the product (Sofu and Ekinci, 2007)
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