Furaanvorming tijdens de productieketen van levensmiddelen: vooruitzichten om het furaangehalte van fruit- en groentegebaseerde systemen te verminderen

Furan is a processing-induced contaminant that is classified as ‘possibly carcinogenic’ to humans. Since the carcinogenic effects can most probably be attributed to a genotoxic mechanism, furan concentrations in foods should be kept as low as reasonably achievable. Heat-treated, shelf-stable fruit- and vegetable-based products (e.g. jarred baby foods, ready-to-eat soups, sauces and juices) are important contributors to the furan exposure of children and adults. As a step towards furan reduction in such products, this doctoral thesis addressed the need for quantitative insight into the effects of (i) the thermal preservation process, (ii) the product formulation and (iii) the storage conditions on furan formation in fruit- and vegetable-based systems. The thermal preservation process clearly has a large impact on the formation of furan. Traditionally, heating processes of low-acid, semisolid foods such as purées, soups and sauces are characterized by long treatment times at a high temperature to obtain shelf-stable products. In this doctoral thesis, innovative high-pressure high-temperature (HPHT) processing presented itself as an interesting alternative for furan reduction in such products. For a fair comparison with conventional thermal processing, a range of individual vegetable purées was HPHT- and thermally treated aiming at an equivalent thermal impact on Clostridium botulinum spore inactivation (F0 = 5 min). The highest furan concentrations were found in the thermally treated purées (~0.1 MPa, 117 °C), with red beet (15 ng/g purée), bell pepper (11 ng/g purée) and spinach (10 ng/g purée) being identified as possible risk matrices. Following HPHT treatment, the furan concentration of the vegetable purées decreased to levels close to the analytical limits (1-2 ng/g purée). Since a pressure level of 600 MPa did not significantly decrease the rate of furan formation in spinach purée, the observed furan reduction could be explained by the application of compression heat, resulting in faster heating and cooling rates compared to conventional thermal processing. Besides process optimization or the application of an alternative processing technique, the furan concentration of shelf-stable fruit- and vegetable-based foods can also be reduced by product reformulation. Basic food constituents such as sugars, ascorbic acid, fatty acids and carotenoids have all been reported as possible furan precursors. Based on an I-optimal experimental design with potato purées spiked at different concentration levels of these precursors, reducing the amount of monosaccharides or adjusting the redox conditions of the matrix could be suggested as two possible approaches for furan mitigation. Significant correlations were observed between the furan concentration following thermal sterilization (121 °C, F0 = 15 min) and the initial concentrations of fructose and glucose, which could most probably be attributed to their high, but realistic concentrations (each up to 5 g/100 g purée) in the product. Under the given conditions (ca. pH 6, high-moisture foods), ascorbic acid showed a clear reducing effect on furan formation as an antioxidant, possibly by protecting polyunsaturated fatty acids against oxidative degradation. Next to the interventions at the precursor level, the furan formation can also be affected by adjusting the oxygen availability and/or pH. Lowering the oxygen concentration (0.1-1.8 mg/l) or an acid pH of 3 resulted in a clear furan reduction for a similar range of potato purées. Following thermal treatment for preservation, the product quality of shelf-stable fruit- and vegetable-based foods can further be altered by chemical deterioration reactions during storage. For the first time in the literature, this doctoral thesis showed that most fruit- and vegetable-based foods have a substantial potential for furan formation during storage, irrespective of the thermal intensity applied for preservation (i.e., pasteurization or sterilization). The furan concentrations of orange and mango juices largely increased during the storage phase (8-32 weeks at 20-42 °C), rather than during pasteurization (92 °C, 30 s). The furan concentrations of sterilized (117 °C, F0 = 5 min) vegetable purées increased in a matrix-specific manner. Potato (a commonly used ingredient of shelf-stable products) was one of the vegetable types that was most susceptible to furan formation during storage (5 months at 35 °C). By storing the selected fruit- and vegetable-based systems at moderate (room temperature) or refrigerated (4 °C) temperatures, furan formation could be reduced to a minimum. Moreover, the furan concentration of sterilized and stored vegetable purées could be decreased by evaporative losses during the reheating step prior to consumption. This doctoral thesis demonstrated the potential of furan mitigation measures throughout the processing chain of fruit- and vegetable-based food systems. Ultimately, the experimental attempts should result in the establishment of an industrial toolbox for furan mitigation, similar to acrylamide. By providing possible furan mitigation measures at different steps of the food processing chain (thermal preservation process, product formulation and storage), such a toolbox should enable food processors to reduce the furan concentration of fruit- and vegetable-based foods, with limited adverse side effects on other important food safety or quality attributes.nrpages: 150status: publishe