Nuchev sponsored Massey University student, Abby Li, is presenting her research work next week at the Degree Show in Auckland New Zealand.by Xiaoqi Li: Institute of Food, Nutrition & Human Health, Massey University, Auckland, New Zealand
Goat milk and derived milk products are increasingly become important food source due to their health benefits of higher digestibility compared to bovine milk (Jandal,1996; García, Rovira, Boutoial & López, 2013) and low allergenic (Park, 2007; García, Rovira, Boutoial & López, 2013 ). However, unlike the consumer acceptance of goat milk cheese, the development of the highly beneficial drinking milk products has been held back by the unique “goaty” flavour. Thereby, the understanding of the development of “goaty flavour” will be important so as to minimise the unfavourable flavour in goat milk products.
The objective of this project was to determine the impact of pasteurisation and ultra high temperature (UHT) heat treatment on the “goaty flavour” of fresh goat milk.
Fresh goat milk was heat treated at 72°C for 15 seconds, 135°C for 5 and 15 seconds, 140°C for 5 and 15 seconds respectively. All samples were stored in the fridge at 4°C. Heat processed goat milk samples were tested for the microbiological safety, and evaluated by a trained sensory panel during storage for 14 days.
The heat treated goat milk was tested for Coliforms, Listeria and Salmonella prior to sensory evaluation. Aerobic plate counts were used to examine the level of microorganisms in the milk products as an indication of the effectiveness of heat treatment processes.
Goats milk products were evaluated by trained sensory panelists to describe the goat milk during the 14 days storage time.
Results and Discussion
The aerobic plate counts (APC) in the pasteurised goat milk after heat treatment was 140 cfu/ml which was less than 50000 cfu/ml (Foodsafty, 2014), and the APC in UHT milk samples was 0 cfu/ml indicateing that the heat treatments were effective in inactivating the microorganisms. During storage the plate counts were less than 150 cfu/ml for the pasteurised sample, and there was no colony formed in all UHT samples. No coliforms, Listeria or Salmonella were detected.
Sensory results showed that the typical mutton and goaty flavours of goat milk products can be easily picked up by sensory panellists. Furthermore, these flavours didn’t increase during a storage time period of 14 days (Fig 1 & 2). Pasteurised goats milk samples had least mutton and goaty flavours compared to the UHT milk samples.
Laboratory processed fresh goat milk shows the existence of the goaty flavours. The higher processing temperature and longer processing holding time increased goaty flavour. There was no significant change can be detected by sensory panel of goaty flavour during storage at 4ºC.
I would like to thank Nuchev Ltd, who kindly sponsored this research. I wish to thank Mr. Steve Howse for his patient guidance and enthusiastic encouragement during the research.
I would also like to express my very great appreciation to Dr John Grigor and A/Prof Marie Wong for their valuable and constructive suggestions during the planning and development of this research work.
Food Safety. (2014). Microbiological reference criteria for food. Retrieved from http://www.foodsafety.govt.nz/elibrary/industry/microbiological_reference-guide_assess.pdf
García, V., Rovira, S., Boutoial, K., & López, M. B. (2013) Improvements in goat milk quality: A review. Small Ruminant Research(0). doi: http://dx.doi.org/10.1016/j.smallrumres.
Jandal, J.M., (1996). Comparative aspects of goat and sheep milk. SmallRumin. Res. 22, 177–185.
Park, Y. W., Juárez, M., Ramos, M., & Haenlein, G. F. W. (2007). Physico-chemical characteristics of goat and sheep milk. Small Ruminant Research, 68(1–2), 88-113. doi