查看更多>>摘要：'Seolhyang' strawberries are popular in Asian markets owing to their bright-red color and desirable flavor. However, Seolhyang strawberries have a fragile outer layer and a short shelf-life. Therefore, 'Seolhyang' strawberries are often treated with CO2 to prolong their shelf-life. However, the effects of high CO2 treatment on the quality of Seolhyang strawberries are unclear. Herein, the effects of a short-term high CO2 treatment on the decay rate, firmness, color, targeted metabolite profile, and antioxidant activity of Seolhyang strawberries in two ripening stages (i.e., half-red and bright-red) were investigated during a 9-day cold storage period. Targeted metabolites (i.e., sugars, organic acids, and anthocyanins) were investigated using HPLC and/or UHPLC-qTOF. CO2-treated strawberries exhibited lower (although not significantly) decay rates than untreated strawberry samples. The bright-red samples contained higher levels of anthocyanins than the half-red samples, regardless of CO2 treatment, during storage. High CO2-treated half-red and bright-red strawberries exhibited firmness, color, and metabolite profiles similar to those of their controls at the final storage time. Interestingly, CO2-treated half-red strawberry samples showed higher antioxidant activity than the control. Thus, CO2 treatment may prolong the shelf-life of Seolhyang strawberries without loss of quality based on improving their targeted metabolite profiles and antioxidant activity.
查看更多>>摘要：Although hazelnuts are mostly consumed after toasting and mixed with other ingredients, for manufactures it is important to have efficient quality control tests on the raw product that they purchase from farmers and suppliers. This study explores the possibility to predict sensory quality of raw hazelnuts, classified according to industrial sensory evaluation, using volatilome analysis through Proton Transfer Reaction Mass Spectrometry (PTR-MS) rapid fingerprinting. Firstly, the link between volatile markers for different visual and sensory defects was investigated. Uncompliant hazelnuts showed higher concentrations for a larger number of volatile organic compounds (VOCs) than compliant samples, including some key hazelnuts odorants like 5-methyl-4-heptanone, 5-propyldihydro-2(3H)-furanone, octanal, 2,4-nonadienal and hexanal. Secondly, by mixing defective and good quality hazelnuts, the method sensitivity in recognizing defects percentage was determined. For about 13% of the detected mass peaks, the method was able to discriminate samples containing 20% of hazelnuts with unacceptable quality from good quality samples. Finally, unsupervised data clustering of VOCs fingerprints obtained with different precursor ions (H3O+, NO+ and O-2(+)) provided a correct classification rate higher than 90% for all ions. The applied methodology is suitable to support sensory quality control programs of raw hazelnuts in confectionary industries.
查看更多>>摘要：Radio frequency (RF) heating has been widely applied for pasteurizing food products. The pasteurization mechanism of pathogens using RF heating is still not clear. In this study, a 27.12 MHz RF system was used to process walnut shells (9%, w.b.) inoculated with S. aureus ATCC 25923. The changes on the gene level of S. aureus ATCC 25923 were evaluated by transcriptomics analysis. Results showed that treatment of S. aureus cells with RF heating resulted in the damage of cell integrity, as observed by scanning electron microscopy, sublethal damage detection, and extracellular adenosine triphosphate (ATP) detection analyses. A total of 449 differentially expressed genes was associated with nucleic-acid metabolism, translation, energy metabolism, cell membrane, and cell wall biosynthesis after RF treatment. Lipid metabolism-related genes (gcdH, ALDH, fadD, fadN, etc.) were all up-regulated, while cell wall synthesis related genes (SgtB, LysC, asd, tag, etc.) were down-regulated more than 2-fold after RF treatment. These results indicated that RF heating disrupted the cell membrane homeostasis and inhibited the synthesis of cell wall. In addition, the translational activity and energy metabolism were also altered after RF treatment. These results provide valuable insights into the pasteurization mechanism of S. aureus ATCC 25923 treated by RF heating.
查看更多>>摘要：A higher fermentation capability and quality of a rice wine was achieved, using mixed fungal (Rhizopus chinonsis R01, Asperigillus niger A20, Mucor pusillus M05 and Saccharomyces cerevisiae S10) starter fermentation of japonica rice supplemented with a-amylase (AM), glucoamylase (GAM) and acid protease (AP). Results showed that alcohol content, free amino acids (FAA) and volatile flavor substances concentrations were increased by 49.22%, 85.54%, and 25.71% compared with the control group respectively. To understand the role of enzymes during rice wine brewing, the effects of hydrolases on chemical and physical properties of cooking rice, on the yeast growth, enzyme productivity of molds were determined. Rice starch was hydrolyzed effectively by AM and GAM, the viscosity reduced significantly, the enzyme contact area expanded, which accelerated the further hydrolysis of japonica rice. Increase of hydrolysate promoted the fungi growth, while improved the ability of molds to produce enzymes. AP promoted the protease activity of M. pusillus M05 and A. niger A20, improved protein utilization, increased the content of FAA and formed higher level of flavor substances in rice wine. The results indicate that hydrolase addition can change the physic-chemical state of the mash to enhance microbial biotransformation and modify flavor metabolism.
NSTL
Elsevier