Abstract
The individually quick-frozen (IQF) method is used to produce high-quality frozen food by freezing an individual piece of food separately from the remaining food. In this study, the effect of various freezing and thawing combinations on the quality preservation of Pleurotus eryngii (king oyster mushroom) was investigated. For this purpose, diced and mini P. eryngii mushrooms were frozen by natural freezing (NF, − 20 °C) or IQF (− 62.5 °C and speed 8.23 m/s) methods and thawed using three thawing methods—flowing water thawing (FT, 4 °C), microwave thawing (MT, 620 W), or natural air convection thawing (NT, 20 ± 5 °C). Quality characteristics, such as thawing loss, texture, water holding capacity, color, microstructure, and sensory quality, were evaluated. MT showed the most rapid thawing time, followed by FT and NT for all the samples. The results showed that thawing curve, water holding capacity, and hardness of IQF samples were better than those of NF samples after NT, FT, and MT. Scanning electron microscopy analysis revealed that cell integrity of the IQF sample was better than that of the NF sample. MT is the fastest of the thawing methods, but thawing after NF yielded a sample closest to the fresh mushroom sample. Therefore, when combined with NT, IQF minimized the quality changes in frozen diced and mini P. eryngii mushrooms. This study showed that the IQF technology can be used as a new preservation and distribution method of mushroom.
Highlights
Mushrooms are widely used in Asian countries because of their high food value and excellent medicinal value; they are gaining increasing attention of researchers, especially in the prevention of certain diseases or improvement in health [1,2,3]
All the samples revealed that the thawing process slowed noticeably when the temperature was above 0 °C
In case of natural air convection thawing (NT), mini mushrooms frozen by natural air convection freezing (NF) took the longest thawing time of 42.48 min, and those frozen by individually quick-frozen (IQF) took 38.56 min to reach 4 °C
Summary
Mushrooms are widely used in Asian countries because of their high food value and excellent medicinal value; they are gaining increasing attention of researchers, especially in the prevention of certain diseases or improvement in health [1,2,3]. Pleurotus eryngii (king oyster mushroom) is widely used because of its culinary qualities, attractive texture, and flavor preferred by the consumers as well as its pharmaceutical properties It is mainly cultivated in China and Japan, and its market share in Korea is higher than that of the other mushroom varieties [4,5,6,7]. In the food industry, freezing is one of the most important and effective processing technologies for preserving fruits and vegetables to maintain their quality and nutritional properties. It is widely used as a post-harvest treatment of mushrooms [9, 13, 14].
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