Flow microwave pasteurization (MW) is an increasingly popular technique for liquid food preservation. Due to its rapid and direct heating, it has the potential to producea better quality final product than traditional pasteurization (PT). The following is a pioneering study on the effect of MW on iridoid compounds in blue honeysuckle berry products.

The aim of the study was to determine the effect of MW (2100, 2400, 2700 and 3000 W) and PT (90°C/10 min) on the content of selected bioactive components in blue honeysuckle berry nectars of different varieties (Aurora—AUR and Indigo—IND). Quantitative and qualitative analysis of vitamin C, anthocyanins, phenolic acids and iridoids was determined by means of high-performance liquid chromatography.

AUR showed a greater decrease in vitamin C content due to preservation (18-39% for MW; 81% for PT) than for IND (9-22% for MW; 35% for PT). MW caused a decrease in the content of the sum of identified anthocyanins by 2-3% after MW preservation in AUR and an increase of 3-5% in IND; in contrast, PT caused a decrease of 15 and 11% for in AUR and IND, respectively. The sum of identified phenolic acids as a result of preservation decreased by 9-20% in AUR and by 3-10% in IND. For the sum of iridoids, the degradation change in IND was up to 5%, while in AUR, it was up to 1%. More varied relationships were observed for individual compounds as opposed to sums. Chlorogenic acid content increased in AUR by 3% and in IND by 7%, in contrast with the other phenolic acids and iridoids.

Further research is needed to optimize the parameters of microwave flow pasteurization and determine the effect on other bioactive compounds and microbial inactivation.