Quantification of vitamin B12: evaluation of the impact of nonthermal (HP, PEF and UV-C) and thermal technologies of processing in milk

Abstract

The proportion of the world’s population over 60 years is estimated to almost double from 12% to 22% by 2050. Ageing induces diseases in the elderly, such as vitamin B12 deficiency, which is considered a public health issue. Milk is considered one of the main sources of this vitamin, containing 0.54 µg of B12 / 100 g of milk, contributing to the supply of a great part of the recommended daily dose (2.4 µg of B12) for good health. However, thermal treatments such as pasteurization and ultra high temperature (UHT) widely applied by food industries have been claimed to compromise B12 levels. On the other hand, nonthermal technologies such as high pressure (HP), pulsed electric field (PEF) and ultraviolet light (UV-C) have been studied and pointed out as mild treatments with low impact on the chemical characteristics of milk constituents. Such effects have been reported from the point of view of fat, proteins and other components, but no information has been reported on the impact of these technologies on B12 for HP and PEF processing. Furthermore, the impact of heat has been mentioned in the literature, but to the best of our knowledge, no studies have been done on the kinetics of thermal degradation of B12, considering the effects of high temperatures. So, the present thesis aimed to investigate these aspects. In the case of the nonthermal technologies, HP and PEF did not impact B12 levels, being considered HP at 600 MPa the most promising condition to treat milk keeping B12 levels and providing a safe product regarding microbial inactivation aspects. In the other cases (HP at 400 and 500 MPa and PEF 12 µs), although vitamin concentration was not affected, a more pronounced microbial count was obtained. In the case of UV-C light processing, B12 levels showed a tendency to diminish according to the most intense dose applied in the samples, in which the 18 mJ / cm2 led to a reduction of 10% of B12 concentration compared to the control. However, no microbial inactivation was observed in the samples treated with UV-C light. From the point of view of the kinetic studies, the thermal degradation of B12 was confirmed for temperatures in the range of 100 to 140 oC. The activation energy of 130 ± 5 kJ / mol was obtained, and the activation enthalpy and entropy were 126 ± 5 kJ / mol and 19 ± 14 J / mol.K, respectively, demonstrating that the thermal degradation of this vitamin is a process dependent on the temperature, in which the molecule undergoes the formation of non-bioactive products. The studies demonstrated the importance of considering nonthermal technologies to treat milk and the need for better knowledge about the extension of thermal treatments on B12 degradation. Both studies can contribute to having alternative processing and/or conditions to treat milk, maintaining B12 levels in the product, which is essential to supply the requirements of this vitamin for a good health condition, mainly in the elderly population.