Influence of Pre-treatment Techniques on Quality of Vacuum-Fried Carrot Chips

The influence of various pre-treatments on the physicochemical properties of vacuum-fried (VF) carrot chips, including blanching (85°C for 3.5 min), blanching combined with drying (85°C for 3.5 min followed by drying at 70°C for 1 h 30 min), blanching combined with freezing (85°C for 3.5 min followed by freezing at -20°C for 4 to 5 h), freezing (-18°C overnight), and edible gum coating (dipping in 1.5% guar gum for 5 min), was compared with untreated (control) and atmospheric-fried carrot chips. The processing conditions, such as frying temperature (100°C), frying pressure (9 kPa), and frying time (20 min), were selected for the pre-treatment study. Refined palm oil was used for vacuum frying, and de-oiling was carried out at 1000 rpm for 10 min. Quality parameters such as oil content, moisture content, water activity, total yield, color, and sensory value were determined using standard procedures. The results revealed that the lowest moisture content (2.15%) and water activity (0.214) were observed in vacuum-fried carrot chips that underwent the blanching combined with drying pre-treatment. The lowest oil content (10.04%) was recorded in vacuum-fried edible gum-coated chips. Frozen pre-treated vacuum-fried carrot chips had the lowest hardness value of 1.282 N, and the maximum colour values were L* (38.92), a* (22.85), and b* (27.86). Based on the quality parameters and sensory evaluation of the vacuum-fried carrot chips, the freezing pre-treatment was found to be superior among the pre-treatments.