Effect of Storage, Oxygen and Concentration on the Levels of Key Volatiles in Processed Orange Juice

The Impact of Sweetener Type on Physicochemical Properties, Antioxidant Activity and Rheology of Guava Nectar during Storage Time

This study aimed to evaluate the differences in physicochemical properties, antioxidant properties, and rheology between guava nectar with sucrose and guava nectar with neotame and stevia addition (0.01% and 0.05%). All parameters were investigated during refrigerated storage at 4 °C for 15 days. The result showed that all sweetened guava juice samples led to the juice with the greatest presence of overall appearance and antioxidant property. The flow behavior of sweetened guava juice was shear-thinning which was not different from guava juice without sweetener. However, the major volatile flavor compounds identified in all guava juice samples were β-caryophyllene, α-caryophyllene, bisabolene, aromadendrene, α-humulene, and nerolidol, which is not different from guava juice without sweeteners during storage. It indicated that stevia and neotame are good alternative sweeteners to produce low caloric juice production.

Changes of aroma compounds and qualities of freshly-squeezed orange juice during storage

This study focused on the changes of physicochemical and microbiological properties and aroma compounds of freshly-squeezed orange juice during storage at different temperatures. Aroma compounds were analyzed by solid-phase microextraction-gas chromatography-mass spectrometry (SPME-GC-MS). The results showed that the total aerobic plate counts of orange juice stored at room temperature and 37 °C was far more than 4 °C. Totally 33 aroma compounds were determined in these orange juices. Significant differences on the aroma compounds in orange juices stored at different temperatures were observed in the present study. Most of the terpenes decreased at 4 °C after 15 days' storage, while 10 and 8 terpenes increased during storage at room temperature and 37 °C. α-Terpineol and p-vinylguaiacol were the only off-flavor compounds found in juice stored at 4 °C and room temperature at late storage respectively. While terpinen-4-ol, 4-ethylguaiacol and p-vinylguaiacol were found in juice stored at 37 °C at late storage. α-Terpineol was the only off-flavor compound found in orange juice stored at 4 °C.