Search

Blueberry juice has been found to undergo severe browning after treatment and cold storage, such as processing by high hydrostatic pressure (HHP) at 550 MPa/10 min/25 °C followed storage at 4 °C for 4 days. This browning may be due to the degradation of anthocyanin (AC) in the berries. Therefore, in this study, gallic acid (GA), ferulic acid (FA), ascorbic acid (VC), citric acid (CA), tea polyphenol (TP) and α-tocopherol (VE) were compared to determine their ability to improve the stability of the AC in HHP-treated blueberry juice. The juice was combined with the six abovementioned antioxidants at different concentrations, then treated by HHP at 550 MPa/10 min/25 °C and stored at 4 °C for 20 days. Thereafter, the pH levels, degrees °Brix, color parameters, total AC content and polyphenol oxidase (PPO) activity of the blueberry juice blend were measured and compared. Gallic acid at 2 g/L was found to be the most effective antioxidant to protect against AC degradation. After storage at 4 °C for 20 days, the AC content of the juice with no added antioxidants had decreased by 62.27% with a PPO relative activity of 50.78%, while the AC content of juice supplemented with 2 g/L GA had decreased by 13.42% with a PPO relative activity of 28.13%. The results of this study, thus, suggest that GA can stabilize the structure of AC in blueberry juice and reduce PPO activity, which may be beneficial in guiding the production of blueberry juice with high AC retention. [ABSTRACT FROM AUTHOR]

Summary: A blueberry–grape–pineapple–cantaloupe juice blend was copigmented with gallic acid (GA) firstly and treated by high‐pressure processing (HPP) at 550 MPa, 25 °C for 5 min, ultrasound (US) at 520 W, 40 °C for 10 min, or heat treatment (HT) at 90 °C for 3 min to determine their influence on its physicochemical qualities. The shelf lives of HPP‐, US‐ and HT‐juice blends were 72, 48 and 88 days, respectively. The total anthocyanins (ACs), ascorbic acid and total phenols content in juice blends treated by HPP, US and HT did not change immediately after treatment or during the first 16 days' storage. However, after the three treatments, the total ACs, ascorbic acid and total phenols content in juice blends decreased in the following order after 16 days: US > HPP > HT. The HPP‐ and US‐treated juices were superior to the HT‐treated juices regarding flavour, and in the preservation of more types and relative content of esters and aldehydes. In conclusion, GA improved the total ACs and ascorbic acid stability in the juice, while the flavour of the HPP‐ and US‐treated juices surpasses that of HT‐treated juice. Therefore, the HPP treatment was deemed to be more advantageous and had greater market potential for short‐term storage. [ABSTRACT FROM AUTHOR]

Summary: This study investigated the effect of ultrafiltration (UF) combined with high‐pressure processing (HPP) at 550 MPa, 25 °C for 5 min, ultrasound (US) at 520 W, 40 °C for 10 min and heat treatment (HT) at 90 °C for 3 min on the microbial, physicochemical and sensory properties of a blueberry–grape–pineapple–cantaloupe juice blend during 104 days of storage at 4 °C. After UF, the shelf life of the HPP‐ and US‐treated clear juice blends were 104 and 72 days during the storage at 4 °C respectively. HPP, US and HT treatment minimally affected the anthocyanin and total phenol contents, while HPP better maintained the ascorbic acid levels and sensory properties in the clear juice blend during the storage. Therefore, HPP combined with UF was identified as a prospective processing technique in the fruit juice industry. [ABSTRACT FROM AUTHOR]