Development and Performance Investigation of an Inflatable Solar Drying Technology for Oyster Mushroom

Nguyen Van Hung,Marvin Tala,Ampy Paulo Roxas,Carlito Balingbing,Lei Anne Fuertes,Martin Gummert

doi:10.3390/en13164122

Abstract

We developed an inflatable solar dryer for mushroom drying, which was adapted from the Solar Bubble DryerTM originally designed for paddy drying. The improved dryer with an added perforated elevated floor ensured the quality without any requirement of mixing or turning of the mushrooms during drying. Its drying performance and economic feasibility were evaluated through determination of the drying parameters including moisture content (MC) reduction, mushroom quality, energy efficiency, greenhouse gas emissions, and cost-benefits ratio. Mushroom MC was reduced from 90% down to 40–60% within 2–4 h, corresponding to the drying rate at this stage of 10–20% h−1. At the next stage, it took about 4–6 h corresponding to a drying rate of 2–10% h−1 to reach the required product MC of 8–10%. The color of the dried mushrooms still remained white-cream. The drying process required 4.57 MJ, emitted 0.33 kg CO2e, and required an input cost of 1.86 $US kg of dry product. For the specific case in the Philippines, this can generate a net profit of 468–1468 $US−1 year−1 and the investment will break even in 1.3–4.0 years corresponding to the selling price of dry mushroom of 10–12 $US kg−1. The study developed a solution to improve the solar bubble dryer and verified its drying process for mushroom drying at farm scale. It would add a significant value to farmers’ income as well as a diversified source of nutrient-rich food.

Highlights

World commercial mushroom production is about 8 million tons [1]
Solar Bubble Dryer (SBD) originally used for paddy grain drying was adapted with an additional perforated floor for elevating the mushrooms (Figure 3b)
This modification enables the drying air moving both on the top and underneath of the mushrooms to increase drying efficiency and prevent them from sticking on the bottom plastic film

Summary

Introduction

World commercial mushroom production is about 8 million tons [1]. Out of many varieties, edible mushrooms, such as rice straw mushroom ( called “white button mushroom”), and oyster mushroom are widely cultivated in tropical countries such as China and Vietnam [2,3]. The biological efficiency (ratio between mushroom weight at harvest and dry weight of substrate used for mushroom cultivation) of rice straw mushroom is 5–10% [2], while that of oyster mushroom is 30–130%, depending on the substrates [3,5,6]. These mushrooms are a nutrient-rich food and a livelihood source with healthy protein content [7,8,9]. Nguyen-Van-Hung et al [11] and Le-Vinh-Thuc et al [2] reported that rice straw mushroom production can add 50–100 $US profit to a hectare of rice production

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Conclusion