A microbiological, biochemical and sensory characterisation of bovine milk treated by heat and ultraviolet (UV) light for manufacturing Cheddar cheese

The aim of the study was to quantify microbiological, biochemical and sensory changes in full cream raw milk (RM) processed with high temperature short time (HTST) pasteurisation (P), ultraviolet light treatment (UV) and a combination of UV light treatment and HTST pasteurisation (UVP) in commercial scale production of Cheddar cheese. The three treatments have been compared at a similar level of microbial efficacy. No significant differences were reported on the macro-nutrient composition, however a 35% and 18% reduction in cholesterol in the UV and UVP treatments were observed. HTST treatment (UVP and P) reduced riboflavin and Vitamin B12 in milk by similar to 31% and similar to 18% respectively, with no reduction in riboflavin and Vitamin B12 observed after the UV treatment alone. Lipid oxidation and lipolysis results indicated a significant difference between raw and UVP treated milk (p < 0.05). Protein oxidation results indicated no significant differences except for methionine sulfone, which increased by 67.24% and 87.93% respectively for UV and UVP treatments. Some differences were noted with sensory results, most noticeably on the tallowy' flavour descriptor for the UV treated milk, however customer acceptance of UV treated milk will ultimately determine the acceptability of UV technology as an alternative or adjunct to commercial thermal treatment of milk in cheese production. Industrial relevance: UV light has been proposed as a non-thermal alternative or adjunct to traditional heat treatment for the reduction of micro-organisms in fluids. UV technology presents numerous benefits over traditional preservation, such as use of heat treatment, for example: low cost of installation and maintenance, lower production cost and the reduction of carbon emissions when compared to traditional thermal pasteurisation systems. Furthermore UV technology also offers alternative processing technology in developing countries where production of milk and cheese are done on a small scale. Known limitation for the efficacy of UV as a processing option was its low penetration depth into turbid liquids, such as milk, and the possible negative impact on organic compounds when over-exposed to UV light. New optimised reactor design features of the swirl tube Surepure Turbulator (TM), could potentially negate these negative effects associated with UV treatment due to improved uniformity of treatment. This technology would provide and affordable and accessible processing solution to not only enhance the safety and extend shelf-life of the milk being produced, but will also increase final product quality of secondary dairy products such as Cheddar cheese produced from UV treated milk. These advantages could positively impact on the safety, profitability and sustainability of the agro-industrial sector within such regions. (C) 2014 Elsevier Ltd. All rights reserved.