Effects of intense pulsed light treatment with different intensity on preservation of fresh shiitake mushrooms

Abstract: There is a considerable desire to maintain the nutritional compounds and sensory properties of food products which is vulnerable to traditional processing. Intense pulsed light belonging to non-thermal technology is broadly used in sterilization, enzyme inactivation because of its instantaneous, high intensity and wide spectrum light source. And it was reported in many studies that intense pulsed light could become a suitable alternative strategy to improve the food quality, but limited information exists for edible fungi. For the sake of determining the effectiveness of intense pulsed light treatment on preservation of post-harvest shiitake mushrooms, the variability of its sensory qualities, physiology and aging indices and nutrition qualities by intense pulsed light treatment with different intensity during the storage time were evaluated in this paper. For intense pulsed light treatment, the shiitake mushrooms harvested the same batch were transported back to laboratory on the same day, then removed handles and mud. The preprocessed shiitake mushrooms were divided into four groups randomly, and each was exposed to a dose of 0, 9, 15 and 21 pulses corresponding to 0, 28.8, 48.0 and 67.2 mJ·cm-2, respectively. All samples which packed with freshness protection package were stored at 25 ℃ from 0 to 12 days, while above indices were examined every three days. The results revealed that intense pulsed light treatment could maintain the colour and flavor of shiitake mushrooms to some extent, whereas the effect of 48.0 mJ·cm-2 treatment group was the best that sensory qualities could retain well until 9th day of storage. Moreover, physiology indices of shiitake mushrooms including weight loss rate, firmness and browning degree deteriorated with the prolongation of storage time. At the end of preservation period (the 12th day), however, the weight loss rate of shiitake mushrooms of intense pulsed light treatment groups was all lower than 5% but the control group attained to 9.77%. The firmness of control group was significantly lower than those of treatment groups, on the contrary, the browning degree of treatment groups were lower than control group (P<0.05). The intermediate and high level of intensities were lower than 28.8 mJ·cm-2, simultaneously. In addition, peroxidase activity, polyphenol oxidase activity and malondialdehyde mass fraction were associated with aging indices. Despite the peroxidase and polyphenol oxidase activity of shiitake mushrooms increased at early stage, they decreased at later period. At the end of storage time, the malondialdehyde mass fraction and the peroxidase activity treated by intense pulsed light were obviously lower than that of untreated, while the polyphenol oxidase activity of 48.0 and 67.2 mJ·cm(2 groups were lower than control group (P<0.05). In fact, the nutrition qualities such as total phenol and reducing sugar mass fraction of shiitake mushroom increased at preliminary and then descended during storage, vitamin C mass fraction declined. In comparison with control, the 28.8, 48.0 and 67.2 mJ·cm(2 treatment groups increased respectively 28.44%, 42.61% and 17.37% for phenol mass fraction, 68.56%, 88.45% and 63.42% for vitamin C, and 12.87%, 96.39% and 54.16% for reducing sugar after 12 days of storage. Therefore, intense pulsed light could significantly retard the decrease of weight loss rate and firmness of the shiitake mushrooms, delay the increase of browning degree and malondialdehyde mass fraction, promote the reduction of peroxidase and polyphenol oxidase activity, and reduce the loss of total phenol, vitamin C and reducing sugar during the storage time. The effects of maintaining the nutrition qualities of shiitake mushrooms in 48.8 mJ·cm(2 treatment group was the best. The above results indicated intense pulsed light treatment could be available for extending the preservation shelf life of shiitake mushrooms, which has a potential application prospect in controlling the qualities of edible fungi.