Combination of non-thermal technologies for the improvement of strawberry functionality

There is an increasing awareness of the importance of healthy diet among the consumers. Berries and other fruits are rich sources of polyphenols, vitamins and fibre, which can have a high beneficial effect on health due to their potential to reduce risk of cardiovascular, cognitive and cancer diseases etc. [1]. Non-thermal processes have gained importance in recent years due to the increasing demand for fresh foods of high nutritional value, representing an alternative to conventional thermal treatments. The aim of this work was to evaluate the effect of pulsed electric field (PEF) pre-treatment before osmotic dehydration (OD) on mass transfer parameters, antioxidant properties and on the recovery of anthocyanins after simulated in vitro gastrointestinal digestion in strawberry fruits. Strawberry halves were treated with PEF at two different electric field strengths (100 and 200 V cm-1) using 100 near-rectangular shaped pulses, with fixed pulse width of 10 μs and repetition time of 10 ms. Afterwards, samples were subjected to OD treatments carried out in two different hypertonic solutions (40% w/w), one with sucrose and the other one with trehalose, both with addition of 1 % of CaLac. The results showed that there was an increase of water loss upon the application of combined process, while no decrease of solid gain was observed. The antioxidant capacity and activity were higher in PEF treated strawberry, although all the combinations of PEF and OD reduced the values of antioxidant capacity and activity. Four different types of anthocyanins were detected in strawberry before digestion, but after digestion only cyanidin-3-O-glucoside could be quantified in the fruit. Obtained findings suggest that the major anthocyanins present in strawberry are unstable under gastrointestinal conditions, but in vitro simulated digestion indicated that small amounts of cyanidin-3-O-glucoside can reach the intestine where they may be further metabolized and bioactived.