Evaluation of the thermodynamic viability of the formation of benzyl alcohol and toluene from benzoates in milk and fruit yoghurts

Abstract

Recent data in respect of the reduction of benzoates to benzyl alcohol and toluene in orange juice show that a risk of toxic substances formation in fruit yoghurt containing benzoates should be reevaluated. In this article, the thermodynamic viability of the reduction of benzoates to benzyl alcohol and toluene in milk and yoghurt has been substantiated. Tafel region of redox reactions in milk on the platinum electrode was À0.2 to À0.4 V against the silver chloride electrode. It has been demonstrated that spontaneous redox processes in fruit yoghurt include the conversion of oxidised forms of fruit polyphenols to reduced forms.

Electrochemical Basis for Re-evaluating Antioxidant Effect of Redox Substances in Foodstuffs

“…The high reducing ability of redox systems of citrus fruit explains the presence of toluene in orange juice containing benzoate . Redox systems of milk and yogurt are characterized by a lower E 0 than that of polyphenols, which proves data with respect to the thermodynamic viability of the formation of benzyl alcohol and toluene from benzoates in milk and fruit yogurts …”

“…It was proven that the reducing effect of added antioxidants, as well as naturally occurring redox substances of fruit juices, purée, milk, and yogurts, should be taken into account when evaluating the chemical safety of products containing benzoates. , Indeed, reduction conversions of benzoates to benzyl alcohol and to the more reduced substance (toluene) are thermodynamically possible and are in accordance with the reference data. ,− It was shown in practice, using GC-MS, that ascorbic acid reduces benzoic acid to toluene in the model system . However, the presence of catechins in apple juice affects the reducing power of ascorbic acid, therefore toluene was not found in apple juice containing benzoates .…”

“…The polarization curves of fruit juices, with a more negative E 0 of substances of redox systems, is situated in the area of more negative potentials than that for juices with less powerful redox substances. This allowed for forecasting the direction of redox reactions in mixed juices and in fruit yogurts . The quantity of reduced forms of redox substances affects only the oxidation current density but not the area of potentials where polarization curves are situated .…”

“…Yogurt redox systems also include a lactic acid/pyruvic acid couple. , Lactic acid in yogurts can be reversibly oxidized to pyruvic acid, which leads to an additional formation of hydrogen ions . Therefore, the oxidative transformation of lactic acid leads to an increase in active acidity in yogurts and other dairy products.…”

“…Different values of plant polyphenol redox potentials allow the assumption that the reason for the above-mentioned differences may be explained on the basis of the functioning of polyphenols as redox systems, and not as antiradical agents. The value of the redox potential of an antioxidant was shown to be important with respect to the formation of toxic substances in foodstuffs (fruit juice, puree, fruit yogurt) containing benzoates. , …”