Enzymatic browning inhibition and antioxidant activity of pear juice from a new cultivar of asian pear (Pyrus pyrifolia Nakai cv. Sinhwa) with different concentrations of ascorbic acid

Prediction model of browning inhibitor concentration and its optimal composition for mass processing of ready-to-eat fresh-cut 'Fuji' apple (Malus domestica Borkh.) strains

In this study, we optimized the composition of the browning inhibitor for apples and established a prediction model for the browning inhibitor concentration in mass-processed fresh-cut apples based on electrical conductivity measurements. The "Fuji" apples that were harvested in Chungju, Korea, were used for this study. Vitamin C mixture (VCM) and trehalose (Tre) were used as browning inhibitors at a 4% ratio. The browning reaction under Δ3 of BI (browning index) for 5 days was defined as the target shelf-life of the apple flesh. The ΔBI of VCM and Tre was lower than that of VCM by 4%. It is revealed that the electrical conductivity of the browning inhibitor was highly correlated with its concentration and the number of soaked apples. Finally, the regression of the conductivity was fitted as Y = -0.0024 (number of soaked apples) + 0.5111 (R2 = 0.9931). In the validation test, the conductivity must be maintained at 0.4373 S/m or higher to maintain the target anti-browning level of Δ3 or less, which corresponded to ∼80% of the initial qualitative level after manufacture. The conductivity measurement of the browning inhibitor is suitable for monitoring and predicting its concentration in the mass processing of fresh-cut apple production due to the convenience of this method. PRACTICAL APPLICATION: The conductivity measurement of browning inhibitors can be applied not only to the mass processing of apple production but also to the anti-browning treatment of other fruits and vegetables, due to the convenience of this method. From these research results, it is expected to derive a formula that can predict the concentration of browning inhibitors through simple experiments for other fruits or vegetables.

Analysis of factors related to browning of red sour soup during fermentation

As a traditional fermentation food, red sour soup (RSS) is very popular in China. However, browning is always occurred during the process of fermentation, which influences the sensory quality of RSS and limits its further application. Thus, it is meaningful to elucidate the main factors related to browning during the process of fermentation. Herein, the changes in various factors related to browning from group spontaneous (RSS-SF) and inoculant fermentation (RSS-IF) were determined and analyzed. Firstly, the activity changes of enzymes related to browning indicated that browning of group RSS-SF and RSS-IF during fermentation was not related to enzymatic browning. Secondly, path analysis revealed that the main factors related to non-enzymatic browning of group RSS-SF and RSS-IF were oxidation of polyphenol and degradation of ascorbic acid (Vc). The results of this study not only identifies the main factors associate with browning of RSS, but also provides foundation on how to control the browning of RSS in further study.

Effect of ascorbic acid and acerola juice on some quality properties of aseptic filled apple juice

Quality and storability are crucial factors in production of apple juice. The main goal of this study was investigation of the effects of ascorbic acid and acerola juice on the changes of some sensorial parameters and bioactive compounds of aseptically filled and industrial scale produced apple juice during storage for 12 months. While the viscosity and pH of apple juice did not change significantly, the ΔE* peaked (20–30) at month 6 of the storage period. The colour of apple juice was lighter than at the beginning of storage. Maximum total phenolic contents were 1,100, 1,400, and 1,250 mg L−1 in the control, ascorbic acid supplemented, and acerola added samples, respectively. Other parameters (antioxidant capacity, ascorbic acid, browning index, etc.) peaked in month 4. Acerola was a good alternative anti-browning and antioxidant agent for the treatment of apple juice in the processing. The antioxidant capacity of apple juice treated with acerola was higher than with ascorbic acid. The results were obtained with industrial samples, thus, they can serve as a very good base for the optimisation process and industrial production without the need for scale-up.

Sequencing, assembly, annotation, and gene expression: novel insights into browning-resistant Luffa cylindrica

Luffa is a kind of melon crop widely cultivated in temperate regions worldwide. Browning is one of the serious factors affecting the quality of Luffa. Therefore, the molecular mechanism of Luffa browning is of great significance to study. However, the molecular diversity of Luffa cultivars with different browning-resistant abilities has not been well elucidated. In our study, we used high-throughput sequencing to determine the transcriptome of two Luffa cylindrica cultivars '2D-2' and '35D-7'. A total of 115,099 unigenes were clustered, of which 22,607 were differentially expression genes (DEGs). Of these DEGs, 65 encoding polyphenol oxidase, peroxidase, or ascorbate peroxidase were further analyzed. The quantitative real-time PCR (RT-qPCR) data indicated that the expression levels of the LcPPO gene (Accession No.: Cluster-21832.13892) was significantly higher in '35D-7' compared with that in '2D-2'. Several POD genes (Accession No.: Cluster-21832.19847, Cluster-21832.30619 and Cluster-48491.2) were also upregulated. Analysis of the plantTFDB database indicated that some transcription factors such as WRKY gene family may also participate in the regulation of Luffa browning. The results indicated that the divergence of genes expression related to enzymatic reaction may lead to the different browning resistances of Luffa. Our study will provide a theoretical basis for breeding of browning-resistant Luffa.

Effects of high-pressure processing and thermal pasteurization on quality and microbiological safety of jabuticaba (Myrciaria cauliflora) juice during cold storage

The aims of this study were to investigate the effects of high-pressure processing (HPP) on jabuticaba juice characteristics including microbial levels, phenolic compounds, antioxidant activity, and physicochemical properties during 28 days of storage at 4 °C and to perform a sensory evaluation. Juice samples were pressurized at 200, 400, or 600 MPa for 5 min. During thermal processing, juice was treated in a water bath at 90 °C for 60 s. Elevated aerobic plate counts, coliforms, psychrotrophs and yeasts/molds, were not detected in the HPP-400, HPP-600, or thermal-processed (TP) juices and further cold storage showed at least a shelf life of 28 days at 7 °C. All HPP-treated juice had significantly higher antioxidant capacities, higher total phenolic, flavonoid, and monomeric anthocyanin content, and lower browning degrees, compared with the TP. The soluble solid content, titratable acidity and pH were not significantly different in the HPP-400, HPP-600, and TP after 28 days. The ΔE values were significantly increased in all juice samples. Sensory analysis indicated that the HPP-treated juices had higher acceptance and lower bitter perception. In conclusion, HPP treatments above 400 MPa were effective in ensuring microbiological safety, maintaining the overall quality parameters, extending the shelf life, and achieving consumer acceptance.

Melatonin in Apples and Juice: Inhibition of Browning and Microorganism Growth in Apple Juice

Synthetic melatonin (N-acetyl-5-methoxytryptamine, MT) is popular in the US and Asian markets as a health supplement. Here, we identified a naturally occurring melatonin source in apple juice. Melatonin was present in all 18 apple cultivars tested. The highest melatonin level of the edible part of apple was detected in the apple peel. The melatonin content in 'Fuji' apple juice is comparable to the level of its flesh. Melatonin was consumed during the process of juicing due to its interaction with the oxidants. Melatonin addition significantly reduced the juice color change to brown (browning). The mechanism is that melatonin scavenges the free radicals, which was indicated by the ASBT analysis; therefore, inhibiting the conversion of o-diphenolic compounds into quinones. Most importantly, melatonin exhibited powerful anti-microorganism activity in juice. The exact mechanisms of this action are currently unknown. These effects of melatonin can preserve the quality and prolong the shelf life of apple juice. The results provide valuable information regarding commerciall apple juice processing and storage.