Changes in quality parameters, Proline, BetalainsandColor during different thermal processes of Cactus pear (Opuntia ficusindica) juices.

The present study aimed to evaluate some quality parameters like glucose, fructose, HMF and proline contents, betalains and colour retentions of Orange cactus pear juice during different processes of concentration. Juice concentrates were produced by conventional juice cooking at 90°C, 80°C and by rotary evaporation at laboratory scale at 45°C and compared to products obtained at a traditional factory of prickly pear jam (“ROB”), respectively. The resulting products were characterized in terms of colour, browning index and selected quality parameters. In addition to betalains and proline quantifications, proline-betaxanthin ratio was determined. Results shows that fresh prickly pear juice was initially rich in glucose, fructose and proline fulfilling the prerequisites for non-enzymatic browning during processing. However, browning of concentrated juice samples was negligible even after which was attributed to the predominance of proline exhibiting. Interestingly, absorbance indices at 420 nm only increased for cooked samples at 90°C, whereas a slight increment were observed for 80°C cooked and concentrated samples, respectively. Unexpectedly no HMF formation were found after concentration by rotary evaporation.