నైరూప్య

The Effect of Storage Temperature and Duration on the Composition and Bacteriological Quality of Raw Milk

Naceur M’hamdi*, Rachid Bouraoui, Cyrine Darej, Abir Mahjoub, Lamia Hassayoune, Hajer M’hamdi and Latifa Lanouar

Storage of milk production in cold temperatures is a current Tunisian legislation request. However, there is no specification of a limit period for this. The main aim of this study was to assess the effect cold storage and during transport on physicochemical and bacteriological quality of milk in the region of Mahdia. An investigation was carried out on 61 dairy farms in which milk was stored for 2, 24 and 48 hours and transported under refrigeration until the center. Moreover, 61 milk samples were analyzed for bacteriological quality, chemical composition and physical parameters. Results showed that at a temperature less than 5°C the average values of TBC and CT were 7.9 10⁵ and 2.06 10⁴ cfu/ml, respectively and that TBC increases from a temperature ranging from 5 and 7°C to reach an average of 9 10⁵ cfu/ml and from a higher temperature (26°C) the TBC and CT were 3.7 10⁶ and 3.74 10⁴ cfu/ml, respectively. Analysis of variance showed that the physical characteristics (acidity and pH), were significantly affected by length and temperature of storage (P<0.05). The mean value at 26°C is 6.69. For a temperature between 5 and 7°C, pH is 6.7, while for a temperature less than 4°C, the pH is 6.73 and acidity is 15.64 ± 1.04°D. On the other hand, at 26°C, acidity is 15.74 ± 0.73°D. However, no significant effect was noticed of the cold storage and transport on chemical parameters of milk (Fat, protein, lactose and total solid). The mean levels of fat and protein content, lactose and EST are respectively 31.46, 30.69, 49.39 and 114.2 g/l.

Finally, we conclude deterioration in bacteriological quality of the milk after transport.