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.

Pea starch (PS) was treated by high-pressure homogenization (HPH) at different pressures (0, 20, 40, 60, 80 and 100 MPa) three times for 30 min each in order to investigate the effect of HPH treatment on rheological properties and multiscale structure of starch. The results showed that the viscosity and thixotropy of PS initially increased and then decreased with increasing homogenization pressure. The frequency scanning results showed that the storage modulus G’ and loss modulus G” of PS gels were significantly increased after HPH treatment, and the viscosity and elasticity of PS gels were best after 40 MPa treatment. The G’ and G” curves of PS gels showed a turning point in the temperature range of 70–75 ℃. HPH treatment changed the granular morphology, crystal structure and short-range ordered structure of PS. Cracks, pits and holes appeared on the surface of PS granules after HPH treatment, and the particle size distribution changed. Through analysis by X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy, it was found that the proportion of amorphous region of PS increased after 100 MPa treatment, and HPH treatment increased the ratio between peak areas at 1047 and 1022 cm^-1 (R_1047/1022) and the short-range ordered structure of PS. ¹H Nuclear magnetic resonance (NMR) spectroscopy showed that the α-1,4 glycosidic bond and α-1,6 glycosidic bond in PS were damaged, and the branching degree of PS was reduced. This study can provide a theoretical basis for the application of HPH in the regulation of starch rheological properties and multiscale structure.

This study investigated the effects of different durations of ultrasound treatment (0, 10, 20, 30, 40 and 50 min) on the gelatinization, rheological properties, crystal structure, short-range ordered structure, and microstructure of lotus root starch (LS). The results showed that the molecular chain swelled and entanglement increased after ultrasonic treatment, and the gelatinization viscosity increased up to (6059 ± 31) mPa·s. Cracks, and collapses and holes appeared on the surface of starch particles, which promoted the entrance of water molecules and increase the viscoelasticity. Ultrasound treatment destroyed the α-1,6-glycosidic bonds of starch molecules, and broke some branches to form short starch chains, which were rearranged into ordered structures. The number of short-range ordered structures increased, and the R_1047/1022 ratio increased by 3.20%. Short-time ultrasonic treatment (30 min) enhanced the interaction between starch molecules, making the double helix structure more ordered and compact and increasing the T_p and ΔH by 11.09% and 89.21%, respectively. Long-time ultrasonic treatment (40–50 min) was not conducive to the formation of ordered structures. The results of this study can provide a theoretical basis for the application of ultrasonic in regulating the physicochemical properties and multi-scale structure of starch.