Improving the quality of mandarin juice using a combination of filtration and standard homogenization.

Cloud loss and pulp precipitation are serious quality defects of mandarin juice (MJ) which brake on industrialization and need to be overcome by developing stabilization process. Therefore, filtration (FT) and standard homogenization (SH) on improving the cloud stability of MJ and minimizing the loss of major qualities were investigated. The FT-SH combined treatment effectively decreased the minimal particle size below 15 µm and sedimentation rate by 17.30%-74.40%, and increased the cloud value from 7.97% to 332.57%, results in more uniformity and cloud stability of MJ. Moreover, FT reduced the pectin methylesterase (PME) activity by 34.19%-50.96%, browning (ΔE∗ < 3), free and bound phenol contents (27.81% and 59.13%), and aroma intensity (p < 0.05). SH released the free phenols from bound phenols association with cloudiness. The optimum stabilization condition was considered as the 100-mesh + 20 MPa that was obviously improved the cloudiness and minimizing the color, polyphenol and aroma loss.

Simultaneous extraction of phenolic compounds of citrus peel extracts: effect of ultrasound.

Ultrasound-assisted extraction (UAE) has been widely applied in the extraction of a variety of biologically active compounds including phenolic compounds. However, there is an insufficiency of information on simultaneous extraction of these compounds in this area. In the present study, seven phenolic compounds of two families including cinnamic acids (caffeic, p-coumaric, ferulic, sinapic acid), and benzoic acids (protocatechuic, p-hydroxybenzoic, vanillic acid) from citrus (Citrus unshiuMarc) peels were evaluated by UAE. The effects of ultrasonic variables including extraction time, temperature, and ultrasonic power on the yields of seven phenolic acids was investigated. Results showed that the yields of phenolic compounds increased with both ultrasonic time and temperature increased, whereas the opposite occurred with increasing time at higher temperature to some certain. In the case of 40 degrees C, the decrease in the yields of some phenolic compounds was observed with increased time, whereas those of other compounds did not significantly declined. Ultrasonic power has a positive effect on the yields of phenolic acids under study. Among all ultrasound variables, temperature is the most sensitive on stability of phenolic compounds. Moreover, when phenolic compounds from citrus peel extracts were subjected to ultrasound process, the benzoic acids were more stable than the cinnamic acids. Meanwhile, the optimal ultrasound condition was different one compound from another. These were partly attributed to both the differently chemical structures of phenolic acids and the combination effects of ultrasonic variables.

[Variation of betaine and proline contents in wheat seedlings under salt stress].

Glycine betaine (GB) and proline contents of leaf and root were simultaneously determined by HPLC-ESI-MS at seedling stage in the three wheat (Triticum aestivum L.) varieties (salt tolerance from high to low), SW12, Ningchun No.4 and Chinese Spring (C.S) under 5 different salt stress levels. The GB contents among SW12, Ningchun No.4 and C.S were found outstanding difference by ANOVA (P<0.01) and consistent with salt tolerance in wheat. Proline contents were not different among 3 wheat varieties in leaf, but difference was found in the root between the Ningchun No.4 and C.S (P<0.05). The result suggested GB, as one of the materials for osmotic adjustment in plant, had the closest relationship with salt tolerance and could be used as an index of salt tolerance in wheat.

Phenolic compounds and antioxidant activity of extracts from ultrasonic treatment of Satsuma Mandarin (Citrus unshiu Marc.) peels.

Ultrasound-assisted extraction (UAE) was used to extract phenolic compounds from Satsuma mandarin ( Citrus unshiu Marc.) peels (SMP), and maceration extraction (ME) was used as a control. The effects of ultrasonic time (10, 20, 30, 40, 50, and 60 min), temperature (15, 30, and 40 degrees C), and ultrasonic power (3.2, 8, 30, and 56 W) on phenolic compounds were investigated. High-performance liquid chromatography (HPLC) coupled with a photodiode array (PDA) detector was used for the analysis of phenolic acids after alkaline hydrolysis (bound phenolic acids) and flavanone glycosides. The contents of seven phenolic acids (caffeic acid, p-coumaric acid, ferulic acid, sinapic acid, protocatechuic acid, p-hydroxybenzoic acid, and vanillic acid) and two flavanone glycosides (narirutin and hesperidin) in extracts obtained by ultrasonic treatment were significantly higher than in extracts obtained by the maceration method. Moreover, the contents of extracts increased as both treatment time and temperature increased. Ultrasonic power had a positive effect on the contents of extracts. However, the phenolic acids may be degraded by ultrasound at higher temperature for a long time. For example, after ultrasonic treatment at 40 degrees C for 20 min, the contents of caffeic acid, p-coumaric acid, ferulic acid, and p-hydroxybenzoic acid decreased by 48.90, 44.20, 48.23, and 35.33%, respectively. The interaction of ultrasonic parameters probably has a complex effect on the extracts. A linear relationship was observed between Trolox equivalent antioxidant capacity (TEAC) values and total phenolic contents (TPC); the correlation coefficient, R(2), is 0.8288 at 15 degrees C, 0.7706 at 30 degrees C, and 0.8626 at 40 degrees C, respectively. The data indicated that SMPs were rich sources of antioxidants. Furthermore, UAE techniques should be carefully used to enhance the yields of phenolic acids from SMPs.