Reaction calorimetry as a tool for studying the quality of fresh-cut fruits and the efficacy of various preservation treatments

This research was aimed to investigate the quality changes of fresh-cut fruits and the efficacy of various preservation treatments by calorimetric process analyser. First, the study was focus on the development of a novel method based on reaction calorimetry for monitoring the oxidation reaction in foods. The instrument measures the heat flow signal (W) released during the reaction. Such heat flow as well as its integral yields the heat (J) of the reaction. The overall heat was used as index to express the antioxidant capacity of the food samples. The oxidation reaction was investigated between food containing antioxidants and an oxidant reagent (i.e. hydrogen peroxide). The results suggested to use of reaction calorimetry to investigate the antioxidant capacity of fruit juices, fruit puree, tea, coffee and alcoholic beverages, like wines without time consuming sample pre-treatment protocol. The reliability of the approach is assessed through the study of the reaction between hydrogen peroxide and ascorbic acid at different concentrations and pH at 25 C. The second aim was focused to evaluate the efficiency of traditional and innovative preservative treatments on fresh-cut fruits using novel calorimetric approach for monitoring the reaction. Fresh-cut apples (Malus domestica cv. Golden Delicious) were subjected to different stabilization treatments, such as dipping with ascorbic acid solutions (traditional treatment), exposure to UV-C and pulsed light (innovative treatments). The rate of reaction of treated fresh-cut apples was investigated with microcalorimetry. The apple slices treated with ascorbic acid, pulsed light or UV-C treatments showed decrease in the heat flow than control, which confirm the reduction of fruit reaction. The heat flow signal was proportional to the concentration of ascorbic acid or pulsed light dose used, but was not linearly proportional to the fluence of the UV-C treatment. The findings of this study suggest that innovative treatments based on the irradiance of light were able to preserve and enhance the stability of fresh-cut apples, and also suggest the suitability of calorimetry to determine the stability of fresh-cut fruits. Moreover, to accelerate the oxidation reaction in foods, reaction calorimetry method was extended using Fenton type reaction for its industrial application. The method was performed on same samples like previous application of this method, and the results were promising, which made ten times faster of the oxidation of antioxidant compounds (i.e. ascorbic acid) and food samples.