Effect Of Superheated Steam Heating On Fat Related Changes In Reconstitute Milk And Fresh Milk
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Date
2016-04
Authors
Ghazwan Mahdy Salih
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Abstract
Milk and dairy products play main role in human nutrition, which places it first in human nutrition in many countries. Fat and protein are the most important ingredients in milk and can be affected by several factors such as feeding, cow’s age and heat processing. Milk is used as a main ingredient to prepare many types of foods, such as pastries, pies, chocolates and cakes, and can help to improve the overall food characteristics such as texture, colour, and flavour. In this study, superheated steam (SHS) mode was used to heat three types of cow’s milk reconstituted whole milk powder (RWMP), reconstituted omega-3&6 fortified milk powder (FOMP) and raw milk using different parameters temperature and holding time. The SHS heat condition of the RWMP and RFMP were 120-180 °C for 5-15 min, and the raw milk was 130-150 C for 30-60 second. The changes in colour (L*, a* and b*), viscosity, density, pH, lipid oxidation index, fatty acid profile, isomerization fatty acids, vitamins, antioxidant activity, microbiological and volatile compounds were investigated. The study also included optimizing the best conditions of raw milk, heated by SHS and comparison with different heat treatment (microwave and conventional) methods. SHS significantly affected on colour and physical properties of RWMP and FOMP. However, the lipid oxidation index showed stabile to degradations at 120-150 C for 5 min with slight changes at high temperatures and long holding time. From the changes in fatty acids profile, SHS indicated stability relevant to the degradation MUFA and PUFA at the same condition mention above with no isomerization was detect in the SHS heat treatment
to the both of RWMP and RFMP. The vitamins (A retinol, C ascorbic acid and E α-tocopherol) and antioxidant activity (% inhibition of DPPH radical) showed decrease the values with increase the temperatures and holding time. The volatile compounds responsible for the off-flavour sach as hexanal, 2-hexanal were not detected in SHS. Effect of SHS heat treatment of the raw milk also indicates no significant effect on the colour and physical properties except slight changes in viscosity. However, the result did not show any significant differences with respect to lipid oxidation, fatty acid profile, antioxidant activity and volatile compounds. On the milks microbiological quality, SHS fully inactivated pathogenic bacteria (total coliform and Staphylococcus aureus) with reduction in the total bacterial count from 15.33×104 - 63 (cfu. ml-1). Response surface methodology was used to optimize the best conditions of SHS, the result indicate SHS 130 °C for 10 Sec to be the best optimal heating conditions of raw cow’s milk. The comparison between SHS optimum condition with microwave and convention methods was also investigated. The study showed the best with SHS heat treatment to be better than the convention and microwave methods.
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Milk and dairy products play main role , in human nutrition,