MRI visualization of shiitake mycelium growing in logs in order to support shiitake mushroom log cultivation
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ORIGINAL RESEARCH
MRI visualization of shiitake mycelium growing in logs in order to support shiitake mushroom log cultivation Kuniyasu Ogawa
. Takeshi Yashima
Received: 15 May 2020 / Accepted: 20 August 2020 Ó Springer Nature B.V. 2020
Abstract In order to correlate the yield and quality of shiitake mushrooms with the growth process of shiitake mycelium in logs over several years, a noninvasive visualization method using a magnetic resonance imaging (MRI) measurement system was developed. The MRI measurement system had a permanent magnet of 1.0 T magnetic field strength and a 110 mm air gap. The test logs in which grew the shiitake mycelium had a diameter of 43–48 mm, a length of 110–118 mm and a dried mass of 125–135 g. The log was inoculated on one cutting surface after being supplied water, and was placed in a thermostatic chamber (21 °C, about 75% humidity) for 69 days. The test log was observed by MRI, and MR images and T1 maps of shiitake mycelium growing over time were obtained. It was found that the shiitake mycelium has a T1 relaxation time constant longer than 150–200 ms, and its signal intensity in the MR images is smaller than that of water penetrated into a log. When making the MRI measurements, it is necessary
K. Ogawa (&) Department of Mechanical Engineering, Keio University, 3-14-1 Hiyoshi, Kouhoku-ku, Yokohama, Kanagawa 223-8522, Japan e-mail: [email protected] T. Yashima Ishikawa Agriculture and Forestry Research Center, 1-1 Mizuho, Noto-chou, Housu-gun, Ishikawa 927-0311, Japan e-mail: [email protected]
to dry a log to water content of about 20% or less. In addition, a control log with mold was also observed by MRI. The shiitake mycelium can be distinguished from water penetrated into log and mold occurring in the log by combining the T1—signal intensity map and clear recognition of a low-intensity region in MR images acquired at longer echo times. Keywords Shiitake mycelium Log-cultivation T1 relaxation time constant Magnetic resonance imaging
Introduction The production of shiitake (Lentinula edodes) cultivated using logs in Japan in 2016 was about 8,000 tons (National Statistics Center). Log-cultivated shiitakes are popular (Przbylowicz and Donoghue 1988; Wasser 2005; Tokimoto 2010) and expensive because of their good taste and smell compared with that cultivated in woodchip blocks. The report shows that the composition of shiitake varies depending on the growth media used, which are logs or woodchip blocks (MEXT 2015). According to the comparison of shiitake components per 100 g shown in the report, log-cultivated shiitakes have a lower water content (88.3 g), higher carbohydrates (7.6 g) and higher
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Cellulose
energy (23 kcal) than that of woodchip-blocks-cultivated shiitakes (89.6 g, 6.4 g, 20 kcal). A woodchip-block is a mixture in which wood chips of about 5 mm size and rice bran (Oryza sativa) are mixed at a mass ratio of 9:1, water is further added and mixed, and then packed in a plastic bag. Rice bran is ad
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