The change in weight and surface temperature of a pine cone (Pinus sylvestris L.) as a result of microwave irradiation

Abstract

In this article, the author investigates the change of weight and temperature of pine cones in a microwave oven over the following range of microwave irradiation power (PMF): 800, 620, 440, 260 and 130 W. Cones were divided into groups according to their weight and the author examined the influence of PMF on their water content and drying rate. The process is described with the help of mathematical equations and curves. The cones were irradiated in the microwave until all cones of the given group began to open the first scales. Small cones required longer exposure times to PMF than medium and large cones in order to cause scale opening. The most efficient of the five settings was a irradiation power of 620 W with an exposure time to microwaves for no longer than 20 seconds. In the second part of the study, the author analyses the changes of temperature on the cone surface using a thermal imaging camera. The values of surface temperature depended on irradiation power and the duration of irradiation.

Influence of the Duration of Microwave Irradiation of Scots Pine (Pinus sylvestris L.) Cones on the Quality of Harvested Seeds

“…Statistics of the physical parameters of the cones used in the study are presented in Table 2. The physical characteristics of the study material were found to be within the typical range for Europe, where the length of Scots pine cones ranges from 19 to 70 mm, their thickness ranges from 12 to 35 mm [33,34], and their weight ranges from 5 to 18.4 g [1,35]. The mean moisture content was 34%.…”

“…Due to the high processing capacity that these facilities require, the need for regular deliveries of large amounts of cones is high in order to reduce extraction costs. However, this is often not easy to achieve as the availability of cone crops depends on seed years [1]. The most widespread forest tree in Central and Eastern Europe is Scots pine (Pinus sylvestris L.), hence the seed material of this species is typically used for studies.…”

“…Although numerous studies were conducted, no positive effects in terms of significant reduction in extraction time emerged. One of the reasons for this was the high sensitivity of seeds during drying to external factors, such as excessive temperature or inappropriate air humidity [1].…”

“…The effects of microwave irradiation on Scots pine cones were discussed by Aniszewska and Słowiński [27], who determined the maximum exposure time for enabling the extraction of good quality seeds. Aniszewska also investigated an increase in the surface temperature of cones, depending on the microwave irradiation power and duration [1]. Microwave-assisted drying of canola, soybean, and corn was carried out by Hemis et al [28], who concluded that microwaves could lead to cracks in seeds, reducing their quality.…”

“…This would lead to weight loss and initiate the opening of scales, that is, their separation from one another. Such treatment improves the leaning of scales and exposure of seeds in the next phase of the first stage of cone hulling, which is conducted in an extraction chamber or kiln [1]. However, a precondition for the widespread use of microwaves is the investigation of their effects on seed viability.…”