Vacuum frying optimizes quality of fruit-and vegetable-based snacks.

Consumers are demanding more high-quality ready-to-eat fruits and vegetables that do not contain any artificial preservatives. Vacuum frying has the potential to produce healthier snacks that offer improved taste and texture.

Scientists at Texas A&M University evaluated vacuum frying for making snacks from sweet potatoes, green beans, Tommy Atkins mangos and blue potatoes. Their research supports the ability of vacuum-frying technology to provide high-quality fruit and vegetable snacks.

In this research, eight liters of canola oil were poured into a cast aluminum electric pressure cooker. Then, 50 grams of approximately 1.5-mm-thick sample vegetable slices were placed inside a basket in the cooker. The vessel was depressurized, and the lid was closed. At less than 10 Torr, the slices were immersed into the hot oil. The optimum frying temperature was 120 C for all produce except for the sweet potato, which was fried at 130 C. The green beans had to be soaked for 1 hour in a 50% maltodextrin-0.15% citric acid solution before they were fried. Frying time was about 1 to 7 minutes, based on the produce. After they were fried, the slices were blotted with dry paper towels to remove excess oil.

The products were also fried in a traditional deep-fat commercial fryer at 160 C to 165 C for 4 minutes. Color, oil content, the total carotenoid content of the green beans, mangos and sweet potatoes, and the anthocyanin content of the blue potatoes were determined using standard AOAC methods.

A 30-member consumer panel rated the sensory quality of both types of fried snacks using a 1 to 9 hedonic scale. Compared with traditional frying, the oil content of the vacuum-fried mangos and of the green beans was 15% lower. The vacuum-fried blue and sweet potatoes had 5% more oil. The anthocyanin content of the vacuum-fried blue potato was 55% higher.

The total carotenoid content increased by 30% for the green beans and by 80% for the sweet potatoes and mangos. The sensory panelists overwhelmingly preferred the vacuum-fried products for their color, texture, taste and overall quality.

Further information. Rosana Moreira, Biological and Agricultural Engineering Department, Texas A&M University, 2117 TAMU, College Station, TX 77843; phone: 979-847-8794; email: rmoreira@tamu.edu.