Engineering, Energy, Transport AIC

Vitalii YAROPUD – Candidate of Technical Sciences, Associate Professor, Dean of the Faculty of Engineering and Technology, Vinnytsia National Agrarian University (St. Soniachna, 3, Vinnytsia, Ukraine, 21008, e-mail: yaropud77@gmail.com, https://orcid.org/0000-0003-0502-1356).

Petro LAVRENIUK – Recipient of the Third Educational and Scientific Level of the Department of machinery and equipment for agricultural production of Vinnytsia National Agrarian University (3 Soniachna Street, Vinnytsia, 21008, Ukraine, e-mail: lavreniuk.petro.1239@gmail.com, https://orcid.org/0000-0002-2480-7365).

Walnuts are at high risk of oxidative spoilage during storage, transportation and sale. The speed of this process is affected by the chemical composition of the nuts, which varies depending on the variety and region of cultivation. This means that each batch of nuts has a different storage potential. The problem is exacerbated by the lack of an effective system for tracking batches of nuts at all stages: from production to sale. There is also a lack of objective methods for assessing the shelf life of nuts. Because of this, manufacturers and sellers often incorrectly set expiration dates. As a result, according to statistics, more than 30% of walnuts sold in stores have signs of bitterness, which indicates their spoilage.
Preservation of the quality of walnuts depends on a number of key factors, among which the level of humidity, temperature, humidity of the ambient air, access of oxygen, condition of the nuts, packaging materials, storage method and technological processing (peeled, in shell, roasted, etc.) play an important role. Although walnuts are considered a product with a long shelf life, maintaining optimal conditions is critical to maintaining their freshness and flavor.
The aim of the research is to study the kinetics of drying walnuts under the influence of a warm air flow in laboratory conditions.
The results of laboratory studies of the kinetics of drying walnuts with a warm air flow demonstrate that the main process parameters – initial humidity w₀, air temperature T, air flow velocity v and drying duration t – significantly affect the drying rate Vt and the final moisture level wt.
The change in nut moisture wt with time t in all studied conditions occurs gradually. The drying rate Vₜ is the highest at the initial stages and decreases with time due to the depletion of surface moisture. Similarly, with increasing air flow velocity, the drying rate increases. In general, optimization of the drying process involves adjusting the temperature and air flow velocity depending on the desired drying time. High temperature and optimal air flow rate ensure efficient drying. It was found that the delay in temperature change becomes shorter with increasing temperature. Thus, it can be considered that at the initial stage (5 h) of walnut drying, it is advisable to apply high-temperature treatment (80 °C) to improve the heat transfer effect and drying performance, which will further increase the drying rate. Subsequently, it is desirable to reduce the drying temperature to (50 °C).

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