Читать книгу Thermal Food Engineering Operations - NITIN KUMAR - Страница 27

RF dielectric has various applications in lumber, textile, and food industries, etc.

RF treatment is giving after the biscuits baked in cereals, to dry foods (herbs, spices, vegetables, potato products, pasta products), thawing, etc. The efficient role of RF is seen in moisture removal during the baking process.

It is also used for the thawing of meats and fish in large amounts, and its volumetric nature enhances the acceleration in the process without affecting the distribution of temperature throughout the product [54].

1 i) RF application in Fresh food processing:In Fresh fruits: A significant reduction in brown rot was seen when dielectric treatment (27.12MHz, 15kW) was given with hot water. Infection in peaches being reduced using RF heating and brown rots controlled in nectarines. In Fresh Vegetables: Vacuum-packaged Caixin (a green leafy vegetable) with an adequate microbial count resulted in a significant decrease in the number using ohmic heating with a 20 mm gap in electrode without affecting any other property of the material [26].

2 ii) RF heating on fresh meats showed results when treated while meat processing, as reduced E. coli count, shelf life extension wherein it has higher heating uniformity and had a shorter cooking time [31, 75].

3 iii) Significant reduction of A. parasiticus in corns seen using a combination of RF heating with hot air [25, 26].

4 iv) RF heating system in food industries used to inactivate bacteria in wheat flour, caixin, peach, pepper spice, apple juice, stone fruit, almonds, ham, etc., using free-running or 50Ω type system at a frequency of 27.12MHz [31].

5 v) It also used for disinfestation of rice, lentils, legumes, walnuts, etc., using a free-running oscillator at a frequency of 27.12MHz [31].

6 vi) Also used in cooking purposes in beef, egg white, meat emulsion, pork ham, turkey, meat, etc., using free running or 50 ohms at a frequency of 27.12MHz.

7 vii) Used in the thawing of pork, tuna fish, beef using 50 ohms at a frequency of 13.56-27.12MHz [31].

8 viii) For enzyme inactivation in miso paste, apple, myrosinase using 50 ohms at 27.12MHz frequency.

9 ix) Application in roasting and drying of nuts as well for improving energy efficiency and product quality [31].

10 x) Dry-blanching with RF was observed to be an efficient method to treat products in which a 95% reduction in enzyme activity (POD) was seen in 3-7 min. time with a gap of 8-8.6 cm; rehydration enhancement, retention of the textural properties were also recorded [24].

11 xi) Application in wood drying (10-30MHz), agricultural product drying (27MHz), food drying, etc. [79].

12 xii) Production of Biodiesel from moist microalgae: Cell disruption of Algae done using RF heater at a frequency of 27.12MHz and maximum power output of 6kW and the esterification/transesterification reactions were also promoted [48].