INTERNATIONAL JOURNAL OF AGRICULTURE & BIOLOGY ISSN Print: 1560–8530; ISSN Online: 1814–9596 10–049/ZII/2010/12–3–439–442 http://www.fspublishers.org Full Length Article To cite this paper: Siddique, F., F.M. Anjum, N. Huma and A. Jamil, 2010. Effect of different UHT processing temperatures on ash and lactose content of milk during storage at different temperatures. Int. J. Agric. Biol., 12: 439–442 Effect of Different UHT Processing Temperatures on Ash and Lactose Content of Milk during Storage at Different Temperatures FARZANA SIDDIQUE 1 , FAQIR MUHAMMAD ANJUM, NUZHAT HUMA AND AMER JAMIL† National Institute of Food Science and Technology, University of Agriculture, Faisalabad, Pakistan †Department of Biochemistry, University of Agriculture, Faisalabad, Pakistan 1 Corresponding author’s E-Mail: farzanasiddiqueft@gmail.com ABSTRACT Commercial milk and improve quality milk containing total plate count 2.2 × 10 6 and 3.5 × 10 5 cfu/mL and somatic cell count 621,000 and 249,000 per mL, respectively were subjected to different ultra-high temperature (UHT) processing temperatures (135, 138, 141 & 144 o C) and stored at 25 o C and 40 o C temperatures for 90 days. Commercial milk contained significantly lower content of lactose as compared to improved quality milk. More degradation of lactose content was observed in milk stored at 40 o C than at 25 o C temperature. The lactose content decline in UHT milk processed at a temperature 135 o C was lower than at 144 o C temperature. Commercial milk possessed higher ash content than improved quality milk. UHT processing and storage temperatures had no influence on ash content of both milk sources. © 2010 Friends Science Publishers Key Words: Commercial milk; Improved quality milk; Somatic cell count; Total plate count; Storage period INTRODUCTION Milk is a secretion from the mammary glands derived from the milking of healthy Halal milch animals (PSQCA, 2008) it should be free from colostrum. Nature has gifted milk with the attributes of an ideal food. It is highly nutritious containing essential nutrients required for the development of all age groups. The stockpile milk nutrients include the energy providing lactose and fat, the bone forming calcium and other minerals, the body building proteins and health promoting vitamins. Pakistan is ranked as a fifth largest milk producing country in the world with milk production of 43.6 billion liters per year (GOP, 2009). Only 4% of the total milk produced is processed and used in urban areas of the country. Milk may be consumed as fresh, boiled and in powder form. Common milk products are yogurt, ghee, butter milk, butter, cheese and ice cream. By weight, milk and its products makes up nearly one-third of all the food consumed in Pakistan. However, per capita availability of milk in Pakistan is less than the recommended levels of 0.5 L per person per day prescribed by World Health Organization (WHO, 2005). With rapid increase in human population and stress to maximize production of food especially in developing countries, demands the use of technologies for more production and preservation of food. The processors preserve and process the milk by thermal processing to meet the increasing demand of milk round the year in the markets. Various thermal processing techniques are being applied in the dairy industry but among ultra-high temperature (UHT) treated milk has higher acceptability due to hot prolonged summer season in Pakistan. UHT processing is carried out by subjecting milk at a high temperature for a short period of time in order to have a long shelf-life at room temperature (Valero et al., 2001). The thermal processing treatment of milk brings about changes in nutritional, sensoric and technological properties of milk. The intensity of these changes varies widely with changing in processing conditions (Fox & McSweeney, 1998). Milk sterilized by the use of UHT treatment tends to be unstable during storage. This stability is a critical aspect of quality of UHT milk, which limits its use. Lactose a disaccharide sugar is major carbohydrate of milk commonly referred as milk sugar. Basically the milk of the mammals is the solitary source of lactose (Holsinger, 1998) and ranged from 4.4-5.2% with average content of 4.8%. It is a low glycemic index carbohydrate, which makes this sugar beneficial for diabetics (Brew, 2003). Lactose undergoes changes more readily in milk than in the dry state. A series of reactions take place during heat treatment between amino groups of proteins and aldehyde groups of lactose known Maillard reaction. This reaction is much faster at temperatures above 100°C, which results in a change in color and flavor as well as loss in essential amino acids (lysine & arginine) (Manji & Kakuda, 1988; Alfa-