In order to investigate the effect of different thawing methods on the quality of quick frozen Chimonobambusa quadrangularis shoot (QFCQS), five thawing methods, namely, microwave thawing, ultrasonic thawing, natural thawing, thawing in a water bath at 20 ℃ and thawing in a water bath at 50 ℃ were used to treat QFCQS. The changes in the drip loss, hardness, color, basic nutrients, peroxidase (POD), polyphenol oxidase (PPO) and phenylalnine ammonialyase (PAL) activity and microscopic structure of QFCQS were measured after thawing. The results showed that thawing time was significantly different among the five thawing methods (P < 0.05). Microwave thawing reduced the thawing time by 97% compared with natural thawing. The drip loss after thawing was as follows: natural thawing > thawing in a water bath at 50 ℃ > microwave thawing > thawing in a water bath at 20 ℃ > ultrasonic thawing. Furthermore, QFCQS with higher drip loss after thawing had lower hardness. After ultrasonic thawing, the color difference (∆E) of QFCQS was 1.72, and the color change was the smallest. Meanwhile, the nutritional quality was maintained to the largest extent, and the content of vitamin C was 1.35 times higher than that of natural thawing. PPO activity in QFCQS was not significantly changed among the five thawing methods (P > 0.05), while the activities of POD and PAL were the lowest after ultrasonic thawing. As shown in scanning electron microscope (SEM) images, the tissue structure was destroyed to the greatest extent after natural thawing but was maintained well after ultrasonic thawing. The results of this study can provide a theoretical basis for the selection and application of a suitable thawing method for QFCQS.

The quality of five cultivars of Chimonobambusa quadrangularis shoots with color shells (black, yellow, brown, red and green) from Jinfoshan Mountain was systematically analyzed and evaluated in terms of texture, color, protein and amino acid, fat, crude fiber, total sugar, vitamin C, selenium, and aroma. The results showed that there were obvious differences in the color of shell and flesh among cultivars. The a^* value of red shoot shells was -0.07 ± 0.01 and the b^* value of green shoot shells was 27.40 ± 0.99; the flesh of green-shelled shoots had a minimum a^* value of -6.50 ± 0.04. Brown-shelled shoots had moderate hardness ((1934 ± 90) g) and better crispness and chewiness. The five cultivars had water content of more than 92%, protein content of 2.21%-3.16%, fat content of 0.11%-0.21%, and crude fiber content of 1.31%-1.72%. The lowest and highest content of total sugar of (0.62 ± 0.01)% and (1.62 ± 0.03)% were found in green- and brown-shelled shoots, respectively. The content of vitamin C in all five cultivars was 1.22-1.63 mg/100 g, and selenium content ranged from 0.78 to 1.65 μg/100 g. In addition, the content of essential amino acids was as high as (735.53 ± 11.09) mg/100 g in fresh brown-shelled shoots, containing a higher level of protein and total sugar, but a lower level of crude fiber. In contrast, green-shelled shoots had a higher level of crude fiber and selenium but a lower level of total sugar. Hexanal, 2-hexenal, hexanol, trans-2-nonen-1-ol, 2-heptanol, 2-heptanone, and 2,5-heptanedione were identified as the major volatile components of Chimonobambusa quadrangularis shoots, and the volatile composition varied depending on the cultivar. The above findings will provide data support for the consumption, development and utilization of C. quadrangularis shoots with different shell colors.