Energy Consumption, Colour, Texture, Antioxidants, Odours, and Taste Qualities of Litchi Fruit Dried by Intermittent Ohmic Heating

Abstract

To reduce the cost of dried litchi fruit, the processing characteristics and physicochemical properties of litchi were investigated using drying by intermittent ohmic heating (IOH) (intermittent air drying (IAD)) generated by BaTiO3 resistance. Litchi fruit pulp were dried at 70 °C with an air velocity of 1.8 m/s; the drying intermittent profiles were as follows: (1) 20 min drying-on and 5 min drying-off; (2) 20 min drying-on and 10 min drying-off; and (3) 20 min drying-on and 15 min drying-off, which correspond to pulse ratios (PRs) of 1.2, 1.5, and 1.8, respectively. After drying, the water content, energy consumption, vitamin C content, total phenolic content, colour, taste, and odour qualities were assessed. The results suggested that IOH drying requires lower energy consumption and yields higher quality products. The energy consumption of intermittent air drying ranged from 341 kJ∙g−1 to 427 kJ∙g−1. The IAD of 1.2 and 1.5 PR reduced the browning of litchi fruits and gained better product quality. The major components of odour and tastes were explored in dried litchi. The rising PR of IAD enabled a lower retention of methane and sulphur-organic aroma and a higher assessing value of bitterness taste. This study revealed that BaTiO3 is suitable for IOH drying and it resulted in more merits of dried litchi fruit.

Keywords

• e-tongue
• e-nose
• ohmic heating
• phenols
• litchi fruits