Pre-Drying Treatment of Carrots and Cabbage with Extremely Low Frequency Electromagnetic Field

Tubers and cabbage are strategically important crops. However, their volume production is limited by their short shelf-life and vulnerability to spoilage. Drying makes it possible to extend the shelf-life but often damages the quality. As a result, the processing and pre-treatment should be calibrated for optimal parameters. In this research, carrots and white cabbage were treated with an extremely low-frequency electromagnetic field before convective drying to study the effect of various modes on the microbiological profile of the vegetables. The research featured carrots of the Red Core F1 and Borets F1 hybrids and white cabbage of the Olimp F1 and Agressor F1 hybrids. The carrots and cabbage were treated with an extremely low-frequency electromagnetic field (25 Hz, 1 mT, 15 min) and cut into thin bars (0.3–0.5 mm and 0.5–0.7 mm, respectively). After being dried in an Oberhof Fruchttrockner D-47 hot-air dehydrator, the samples were stored in plastic ziplock bags at 25 ± 2°C and a relative air humidity of 75% for 3 months. The QMAFAnM levels were studied in line with Technical Regulation of Customs Union TR CU 021/2011 before storage and after 1 and 3 months. As for the carrot samples, the preliminary treatment with an extremely low-frequency electromagnetic field accelerated the drying process: the dry product yield was 0.4–0.9% lower than in the control samples. The experimental drying process was less intense for cabbage, with the dry product yield being 2.8–3.9% higher than the control. For the carrots, the drying options were 55°C for 7 h and 65°C for 5 h. Both modes provided permissible values of microbial contamination throughout the entire storage period. The preliminary treatment with an extremely low-frequency electromagnetic field reduced the QMAFAnM by 10.7–34.5%. The cabbage samples dried at 65°C for 3 h had permissible values of microbial contamination. However, the experimental pretreatment led to an increase in QMAFAnM by 9.5–12.5% compared to the control. The cabbage samples dried at 55°C for 4 h exceeded the microbial contamination standards for all parameters. The data obtained may help to develop new methods for drying carrots and cabbage using an extremely low-frequency electromagnetic field.