Effect of pulsed-vacuum, hot-air, infrared, and freeze-drying on drying kinetics, energy efficiency, and physicochemical properties of Ginkgo biloba L. seed

摘要

In this research, Ginkgo biloba L. seeds (GBS) were freeze-dried, infrared-dried, hot-air dried, and pulsed-vacuum dried. A detailed analysis of their drying kinetics (drying curve, drying rate curve, effective moisture diffusivity, mathematical modeling), shrinkage and energy efficiency (specific moisture extraction, specific energy consumption), and physicochemical properties (soluble solids, total sugar, reducing sugar, ascorbic acid, phenolics, and tannins) were performed. Results showed drying methods had various effects on different indexes and were confirmed by principal component analysis. The drying process occurred in the falling-rate period. The effective moisture diffusivity values amongst various drying methods ranged from 3.5 x 10(-8) to 7.6 x 10(-8) m(2)/s, which were within the normally expected range for food materials. The exponential model best fitted the experimental results for drying with coefficient of determination (R-2 ) .981 and root mean square error, sum of square error, and reduced chi-square closer to zero than the parabolic and inverse-logarithmic (Log3p1) models. The freeze-dried GBS had the highest nutritional (statistically the same with the fresh GBS) and lower shrinkage; nevertheless, it had the lowest moisture extraction rate and the highest energy consumption. Hot-air dried GBS had the highest shrinkage and lowest nutritional retention. Infrared-dried GBS was superior with the highest non-tannic phenolic, proanthocyanidins content, effective moisture diffusivity, drying rates, and energy efficiency. The current findings indicate that infrared drying is a promising drying technology for GBS and has the potential to be applied on a commercial scale.Practical application Ginkgo seeds (GBS) are utilized as functional food across Asia. In China, ginkgo trees' extensive cultivation has surpassed market requirements, as GBS production could reach 60,000 tons per year. Therefore, there is an urgent need to find new opportunities to take advantage of the availability and usage of GBS regardless of the season and overcome the situation that GBS usage only remains at incipient phases of home-cooked recipes. Drying is a common approach to preserve foods'. Nonetheless, there are some drawbacks to conventional drying method, such as low energy efficiency, lengthy process periods, and a decline in quality attributes. The infrared dryer provided a reduced drying time, highest drying rate, energy efficiency, and good quality; thus, it could be applied in the food industry to hot air and freeze-drying, allowing the drying method for GBS faster. The research provided a predictive mathematical model for the parameter control GBS drying process.