Application of novel microwave-assisted vacuum frying to reduce the oil uptake and improve the quality of potato chips, LWT -Food Science and Technology (2016), ABSTRACT: The objective of this study was to evaluate the ability of 20 microwave-assisted frying (MVF) technology to reduce the oil uptake and improve 21 quality attributes of fried potato chips. Potato chips were produced using MVF and 22 vacuum frying (VF) technologies and the oil uptake, residual moisture content, 23 microstructure, texture (crispness) and color attributes of chips were compared. The 24 effects of microwave power density (12, 16 and 20 W/g), frying temperature (100, 25 110 and 120 ) and vacuum degree (0.065, 0.075 and 0.085 MPa) in MVF were 26 evaluated. Results showed that the oil uptake in MVF samples was significantly lower 27 than VF samples, decreased from 39.14 to 29.35 g oil/100 g dry solid. The moisture 28 evaporation rates were accelerated and the MVF produced crispier chips with better 29 natural color. Higher microwave power densities resulted in faster water evaporation 30 rates and lower breaking force. Higher frying temperature led to faster water 31 evaporation, lower oil content and faster color change. Higher vacuum degree bring 32 about faster water evaporation, lower oil content and less color change. Observation 33 of microstructure showed that the cellular structure and integrity of cell wall in chips 34 was better preserved by MVF.35

The combination of ultrasound and microwave in vacuum frying system was investigated to achieve higher drying efficiency and quality attributes of fried products. Purple-fleshed potato were used as test specimen and different power levels of microwave (0 W, 600 W, 800 W) and ultrasound (0 W, 300 W, 600 W) during vacuum frying. Drying kinetics, dielectric properties, moisture state variation and quality attributes of fried samples were measured in a vacuum frying (VF), and an innovatively designed ultrasound and microwave assisted vacuum frying (USMVF) equipment. The USMVF process markedly increased the moisture evaporation rate and effective moisture diffusivity compared to VF process. The oil uptake was reduced by about 16-34%, the water activity and the shrinkage was lowered, the texture (crispness) and the color of fried samples were greatly improved. The higher ultrasound and microwave power level in USMVF made a greater improvement. The total anthocyanin levels and retention of fried purple-fleshed potato chips was the highest (123.52 mg/100 g solids and 79.51% retention, respectively) among all treatments in US600M800VF process. The SEM analysis revealed a more porous and disruption microstructure in USMVF sample.

With advances in computer, control and sensing technologies it is now possible to design smart dryers at least for certain products. In this paper, a generalized definition of smart (or intelligent) drying technology is proposed and discussed. Recent development in smart drying technology for fresh foods is reviewed briefly. Such technology can be cost effective in detecting and monitoring various food quality parameters which vary with time of the drying process, thus controlling the conditions of drying and producing high quality products. Some important categories of smart drying technology are listed and discussed; these include: biomimetic systems, computer vision technology, microwave dielectric spectroscopy, near infrared reflectance (NIR) spectroscopy, magnetic resonance imaging (MRI), ultrasonic techniques, electrostatic sensor technology and control systems for drying environment. Several latest applications of these smart drying technologies are analyzed. Key factors leading to success of smart drying technologies Downloaded by [Monash University Library] at 13:37 04 December 2014 2 are discussed. Developments, challenges, and applications, which represent a major step toward development of drying technology, are presented.

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The objective of this study was to investigate the effect of low temperature on the microwave-assisted vacuum frying of potato chips. A newly built in-house microwave-assisted frying machine was developed and used in this study. The effect of low temperature on the microwave-assisted vacuum frying of potato chips was investigated via comparing sample properties prepared with the frying temperature of 90℃, 95℃ and 100℃. The experience was taken at the same vacuum degree in every frying process. Parameters of included moisture content, oil content, color parameters (lightness, redness and yellowness), and textures (hardness, crispness) were used to evaluate the effect of different frying temperature on the microwave-assisted vacuum frying of potato chips. Results showed that with lower temperature in microwave-assisted frying, the rate of moisture evaporation of potato chips was slowed down and the time of the ending of frying is prolonged from 10min with the frying temperature 100℃ to 14min with 90℃ and 12min with 95℃.Meanwhile the oil content in fried potato chips Downloaded by [University of Otago] at 19:12 18 July 2015 2 was increased with the lower temperature in microwave-assisted vacuum frying. The breaking force of final products are not significantly (p＞0.05) affected in different frying temperature of microwave-assisted vacuum frying. And the frying temperature of 100℃in microwave-assisted vacuum frying had better preservation of natural color than the lower frying temperature with prolonged frying time. Results showed the temperature is one of the main factor that affects the quality of microwave-assisted vacuum frying of potato chips and the producer could find suitable temperature conditions according the experience.

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