Quality changes of Pleurotus eryngii during vacuum frying

Quick and accurate determination of oil content is extremely important to control the oil content of vacuum fried fruit and vegetable chips. This article uses fresh Pleurotus eryngii as raw materials to explore the influence of different vacuum frying times (0–14 min) on the moisture distribution, oil changes and quality of Pleurotus eryngii strips. The results show that as the frying time increases, the lateral relaxation time required for the taro strips to drop from the highest point of the signal amplitude to smooth becomes shorter and shorter, and the decay rate becomes faster and faster, that is, when the frying time is 14 minutes, The attenuation curvature and velocity are the largest. The oil content and brittleness of Pleurotus eryngii strips are significantly increased (P < 0.05); the water content is significantly reduced (P < 0.05); the hardness first decreases and then increases (P < 0.05); the brightness L* value does not change much, and the color is not Significant change (P > 0.05). At the same time, low-field NMR shows that the high-degree-of-freedom water in the pleurotus eryngii strips migrates to the low-degree-of-freedom water during the vacuum frying process. Among them, the free water in the pleurotus eryngii strips has a large degree of freedom. It has been removed, resulting in poor mobility and increased inability to flow. Part of the free water migrates to the semi-bound water, and most of the semi-bound water migrates outward as free water and then is removed. From this, all peaks are gradually removed. Moving to the left, the total peak area decreases. During the frying process, the T2 relaxation time of Pleurotus eryngii strips all shifted to the left, the total peak area is continuously reduced, the water content is getting less and less, the fat content is getting higher and higher, and the fat content distributed in the edge shell is always higher than Other locations. Low-field nuclear magnetic resonance technology can provide a fast, accurate, and non-destructive method for detecting moisture and grease for the vacuum-fried fruit and vegetable chips. As the frying time increases, the inner contour of the MRI image of Pleurotus eryngii strips gradually becomes blurred, the brightness gradually decreases, the volume shrinks, the less water, and the image interior is close to the background color (blue), indicating that the sample has reached the end of drying; and The grease content is distributed in the edge shell layer higher than other positions. Therefore, the water is continuously removed, the oil signal becomes stronger and stronger, and the oil content of the sample becomes higher and higher.