Dense Phase Carbon Dioxide Treatment Research Articles

Insight into the allergenicity and structure changes of parvalbumin from Trachinotus ovatus induced by dense-phase carbon dioxide

Parvalbumin (PV) is a major allergen in fish, and traditional treatments cannot reduce its sensitization. The effects of dense-phase carbon dioxide (DPCD) treatment on the sensitization and spatial structure of PV in Trachinotus ovatus were evaluated in this study. Western blotting and indirect ELISA were used to determine the allergenicity changes and spatial conformations of PV treated by DPCD. Tris-tricine-SDS-PAGE, circular dichroism, surface hydrophobicity, endogenous fluorescence, UV spectrophotometry, free amino group, total sulfhydryl group and SEM analyses were applied to characterize PV structure. The results showed that DPCD treatment (15 MPa, 30 min, 50 °C) could reduce PV-induced allergic reactions by 39–41 %, which destroyed the normal conformational epitopes and reduced the risk of PV-induced allergy. The secondary structure changed from ordered to disordered with a decreased content of α-helical groups, while the internal hydrophobic groups were exposed. The total sulfhydryl group content decreased significantly (P < 0.05). The surface hydrophobicity and ultraviolet absorption spectrum were enhanced, and the endogenous fluorescence peak shifted to a long wavelength. Meanwhile, the content of free amino groups increased significantly (P < 0.05). This study could provide a theoretical basis and a promising technical approach for reduction of PV allergenicities.

Inactivation effect and kinetics of cathepsin L from white shrimp (Litopenaeus vannamei) by dense phase carbon dioxide

The effects of dense phase carbon dioxide (DPCD) pressure and temperature on the activity of cathepsin L in white shrimp (Litopenaeus vannamei) were studied. Meanwhile the effects of DPCD and heat treatment on the activity of cathepsin L were compared. The results of inactivation kinetics showed that under the same treatment temperature, the inactivation effect of DPCD on cathepsin L increased gradually with the increase of pressure and time. The effect of DPCD pressure on the activity of cathepsin L accorded with the first-order kinetic model. Under the same treatment pressure, with the increase of temperature, the inactivation effect of cathepsin L was significant at the initial stage of DPCD treatment (rapid inactivation period), and decreased with the extension of time (stable inactivation period). The effect of DPCD treatment temperature on cathepsin L activity accorded with the first-order kinetic model at 35 °C, and two-stage kinetic model at 40–60 °C. The difference of relative enzyme activity between the two treatments showed that the dependence of DPCD on temperature was greater than that of heat. Ea, F and Ea, S of DPCD were higher than that of heat, which indicated that cathepsin L was more easily inactivated under DPCD treatment.

Investigation of the relationship between gel strength and microstructure of surimi gel induced by dense phase carbon dioxide based on quantitative analysis

The microstructure of a surimi product determines its quality. Dense phase carbon dioxide (DPCD) can induce surimi gel formation, and the gel strength of the product are significantly better than that of heat-induced gels. The study analysed the changes of the surimi from golden pompano gel strength during the process of DPCD-induced gelation, and the changes of microstructure based on quantitative analysis of scanning electron microscope (SEM) image using ImageJ 1.42 software. The correlations between gel strength and microstructure was investigated. The results showed that the DPCD treatment significantly increased the cross-linking degree (CLD) and gel strength of surimi, compared with the raw surimi. The CLD and gel strength of surimi increased with the increase of DPCD treatment pressure, temperature and time. Quantitative microscopic analysis revealed that the number of pores (n) in the surimi gels increased and then decreased. The apparent porosity (ƞa), average pore area (Aa), average pore perimeter (Pa), fractal dimension (Df) and pore equivalent diameter (d) increased with the increase of DPCD treatment pressure, temperature and time. Correlation analysis showed that the CLD, ƞa, Aa, Pa, Df, d and median pore perimeter (Pc-50) were strongly positively correlated with the gel strength. In contrast, lacunarity (L) is strongly negatively correlated with the gel strength. The linear correlation coefficients between the CLD, ƞa and Df and the gel strength are 0.97, 0.95 and 0.96, respectively. These results provide a technical basis for DPCD to process high-quality surimi products. These findings also offer a novel approach for the testing and evaluating of the quality of surimi products.

Changes in advanced protein structure during dense phase carbon dioxide induced gel formation in golden pompano surimi correlate with gel strength

Changes in protein structure are closely related to gel strength. Dense phase carbon dioxide (DPCD) treatment is an excellent non-thermal food processing method that can be used to induce gel formation in surimi. The sensory, water holding capacity and gel strength of DPCD induced gels are superior to heat-induced gels. Fourier-transform infrared spectroscopy was used to investigate the role of DPCD in the quality of golden pompano surimi gels and changes in protein structure. The intermolecular forces of surimi gels were analyzed in terms of ionic and hydrogen bonds, disulfide covalent and non-disulfide covalent bonds, as well as hydrophobic interactions. Correlation analysis was used to investigate the relationship between the changes in advanced protein structure and gel strength during DPCD-induced gel formation in golden pompano surimi. The results showed that the α-helix and random coil levels of surimi gel were significantly decreased (p &amp;lt; 0.05), while the β-sheet and β-turn content was significantly increased (p &amp;lt; 0.05). The number of ionic and hydrogen bonds in gel proteins decreased significantly (p &amp;lt; 0.05), while the hydrophobic interactions, and disulfide and non-disulfide covalent bonds increased significantly (p &amp;lt; 0.05) after DPCD treatment. Correlation analysis showed that β-sheets, β-turns, hydrophobic interactions, and disulfide and non-disulfide covalent bonds were strongly positively correlated with gel strength, whereas α-helices, random coils, and ionic and hydrogen bonds were strongly negatively correlated with gel strength. Therefore, the α-helix and random coil structures of surimi gels were transformed into β-sheet and β-turn structures after DPCD treatment. Hydrophobic interactions, and disulfide and non-disulfide covalent bonds were the main intermolecular forces during the DPCD-induced gel formation of surimi. Ionic and hydrogen bonds were not the main intermolecular forces. The results provide fundamental data for elucidating the mechanism of DPCD-induced protein gel formation.

Correlation between Water Characteristics and Gel Strength in the Gel Formation of Golden Pompano Surimi Induced by Dense Phase Carbon Dioxide.

The relationship between the gel quality of golden pompano surimi treated with dense phase carbon dioxide (DPCD) and changes in water characteristics was evaluated. Low-field nuclear magnetic resonance (LF-NMR) and nuclear magnetic resonance imaging were used to monitor changes in the water status of surimi gel under different treatment conditions. Whiteness, water-holding capacity and gel strength were used as the quality indicators of the surimi gel. The results showed that DPCD treatment could significantly increase the whiteness of surimi and the strength of the gel, while the water-holding capacity decreased significantly. LF-NMR analysis showed that, as the DPCD treatment intensity increased, the relaxation component T22 shifted to the right, T23 shifted to the left, the proportion of A22 decreased significantly (p < 0.05) and the proportion of A23 increased significantly (p < 0.05). A correlation analysis of water characteristics and gel strength showed that the water-holding capacity of surimi induced by DPCD was strongly positively correlated with gel strength, while A22 and T23 were strongly negatively correlated with gel strength. This study provides helpful insights into the quality control of DPCD in surimi processing and also provides an approach for the quality evaluation and detection of surimi products.

Effect of dense phase carbon dioxide treatment on the flavor, texture, and quality changes in new-paocai

This study investigated the effect of dense phase carbon dioxide (DPCD) treatment on the organoleptic properties of new-paocai. Optimal DPCD treatment (25 MPa/40 °C/40 min) was determined by conducting single-factor and orthogonal experiments with the sensory, bactericidal, and electronic eye evaluations. DPCD treatment (25 MPa/40 °C/40 min) did not significantly affect the nitrite, pH, total acid, and organic acid of the new-paocai brine, and the texture of the radish slices did not display substantial changes. Gas chromatography-mass spectrometry (GC–MS) was employed to characterize the new-paocai brine flavor, revealing 63 and 60 respective flavor compounds with and without DPCD treatment. In addition, DPCD treatment significantly reduced the total organic volatile compound content in the paocai from 48.182 μg/mL to 35.952 μg/mL, DPCD has a great influence on volatile flavor substances. The electronic nose (E-nose) effectively distinguished the flavor differences in the new-paocai brine with and without DPCD treatment. This study combined new food processing technology with traditional food production, could provide a new idea for pickle production technology.

Gelation Process Optimization of Shrimp Surimi Induced by Dense Phase Carbon Dioxide and Quality Evaluation of Gel.

Dense phase carbon dioxide (DPCD) is a new non-thermal method to induce surimi gel. However, the gel quality is affected by many factors, such as DPCD treatment time, temperature, and pressure, which makes it complicated to determine its operating parameters. Box-Behnken and backward linear regression were used to optimize the conditions (temperature, pressure, and treatment time) of DPCD-induced shrimp surimi gel formation, and a model between shrimp surimi gel strength and treatment conditions was developed and validated in the present study. Meanwhile, the heat-induced method was used as a control to analyze the effect of DPCD on the quality of shrimp surimi gel in the present study. The results showed that DPCD treatment affected the strength of shrimp surimi gel significantly, and the pressure of DPCD had the greatest influence on the gel strength of shrimp surimi, followed by time and temperature. When the processing pressure was 30 MPa, the temperature was 55 °C, and the treatment time was 60 min, the gel strength of the shrimp surimi was as high as 197.35 N·mm, which was not significantly different from the simulated value of 198.28 N mm (p > 0.05). The results of the gel quality properties showed that, compared with the heat-induced method, DPCD reduced the nutrient and quality loss of the shrimp surimi gel, and increased the gel strength and gel water-holding capacity. The results of low-field nuclear magnet resonance showed that DPCD increased the binding capacity of shrimp surimi to bound water and immobilized water, and reduced their losses. Gel microstructure further demonstrated that DPCD could improve shrimp surimi gelation properties, characterized by a finer and uniformly dense gel network structure. In summary, DPCD is a potential method for inducing shrimp surimi to form a suitable gel. The prediction model established in this study between DPCD treatment temperature, pressure, time, and gel strength can provide a reference for the production of shrimp surimi by DPCD.

Quark Cheese Processed by Dense-Phase Carbon Dioxide: Shelf-Life Evaluation and Physiochemical, Rheological, Microstructural and Volatile Properties Assessment.

Dense-phase carbon dioxide (DPCD), a novel non-thermal processing technology, has attracted extensive attention due to its excellent performance in food sterilization and enzyme inactivation without quality deterioration. In this work, we aimed to extend the shelf life of quark cheese with DPCD and explore the effect of DPCD treatment as well as storage time on the quality of quark cheese. The sterilization parameters were optimized by means of orthogonal experiments, and the physiochemical, rheological, microstructural and volatile properties of cheese were investigated. The optimal DPCD treatment (20 MPa, 45 min, 55 °C) successfully extended the shelf life of quark cheese due to its inhibition effect on yeast and was able to slow down the proteolysis and alterations in pH and color of cheese. Cheese processed using DPCD after 14-day storage even displayed similar rheological properties to the control at day 0, from which bound water significantly migrated during storage. Moreover, DPCD contributed to the retention of the volatile profile of cheese during storage. This study demonstrated that DPCD is a promising pasteurization technology for quark cheese to improve its quality stability during storage.

Dense phase carbon dioxide treatment of mango in syrup: Microbial and enzyme inactivation, and associated quality change

Dense phase carbon dioxide (DPCD) has been mainly explored as a new non-thermal pasteurization method for liquid foods. However, it's pasteurization efficacy absolutely needs to be further investigated for solid-liquid food mixtures, such as mango in syrup. This study aimed to investigate pasteurization and enzyme inactivation effects for DPCD treatment, and evaluate quality changes by comparing with traditional thermal pasteurization (TP) method. Optimal DPCD treatment (20 MPa, 60 °C, 30 min) was determined by conducting single factor and orthogonal experiments. Staphylococcus aureus CICC 10384 and Escherichia coli CICC 10003, which were selected as representative gram-positive and gram-negative pathogens in mango in syrup, could be completely inactivated by the optical DPCD treatment with initial concentrations of >8-log CFU/mL. Polyphenol oxidase and peroxidase activities could be completely inactivated after the optimal DPCD processing. Less adverse effect on pH and color, and higher amounts of vitamin C and total phenols of samples were observed after DPCD treatment when compared with TP treatment. The shelf-life of mango in syrup treated with DPCD was estimated to be <86 days (25 °C) based on an accelerated shelf-life testing (ASLT). This study demonstrated that DPCD treatment can be considered as a promising pasteurization technology for solid-liquid mixtures without exceedingly influencing their quality attributes.

Quality Changes of Orange Juice after DPCD Treatment

Dense phase carbon dioxide (DPCD) offers advantages of enhanced physical and nutritional qualities during the processing of juices. Here, freshly squeezed orange juice was treated with DPCD, and changes of physical properties and volatile components were investigated and compared with the original untreated and thermally treated samples. The correlations among physiochemical properties were also examined based on Pearson correlation, cluster analysis (CA), and principal component analysis (PCA). Significant correlations were found among the particle size, color parameters, and volatile compounds in the DPCD-treated samples. The 12 parameters were clustered into three groups using CA and PCA, and the eight volatile compounds were separated within the three groups. Nonanal and citronellol were clustered in group I, and they increased for a longer duration of more than 40 min with higher levels than the control. Parameters in group II included D (4,3), L∗, a∗, ethyl butyrate, and trans-2-hexenol, and they linearly decreased after 10–60 min DPCD treatment. The parameters of b∗ and monoterpenes were clustered in group III, and they decreased within 40 min of DPCD treatment and then increased to an intermediate level. In addition, PCA clearly showed that the orange juice samples under DPCD for 10–60 min formed a “U” shape on the two-dimensional plot and that the samples treated by DPCD for 10 min and 20 min were closer to freshly squeezed orange juice than the heat-treated orange juice. This indicated that the nonthermal DPCD process offers the potential to be used more extensively in juice products.

Effect of dense phase carbon dioxide treatment on physicochemical and textural properties of pickled carrot

ABSTRACTDense phase carbon dioxide (DPCD), as a new type of non-thermal technologies, has exhibited a remarkable effect on sterilization to improve the quality of many fruits and vegetables, but little known on the pickled carrot. In this study, the effect of DPCD treatment on physicochemical, textural properties and microbiological quality of pickled carrot treatment was investigated. Our results showed that the optimum condition of DPCD treatment was 30 min under 20 Mpa. Compared with thermal treatment, the DPCD treatment significantly improved the storage quality of the pickled carrot at hardness, color, and β-carotene content. Moreover, DPCD treatment increased the total pectin content and reduced the water-soluble pectin content of the pickled carrot without changing the pectin structures and cell-wall composition. Taken together, our study showed that DPCD is a comprehensive technique to improve the quality of the carrot in pickles processing.

Effects of Dense Phase Carbon Dioxide Treatments on Qualities of Fresh-cut Bitter Gourd

The effect of the dense phase carbon dioxide (DPCD), sodium hypochlorite and blanching treatments on qualities of the fresh-cut bitter gourd was compared. The DPCD treatment reduced the total bacterial count effectively, and the increasing processing time lead to a better effect of sterilization. Meanwhile, the DPCD treatment showed no influence on the total soluble solid content of the fresh-cut bitter gourd. However, the DPCD treatment reduced the ascorbic acid content and pH value of the fresh-cut bitter gourd.

Dense Phase Carbon Dioxide Combined with Mild Heating Induced Myosin Denaturation, Texture Improvement and Gel Properties of Sausage

AbstractThe aim of this study was to investigate the influence of dense phase carbon dioxide (DPCD) combined with mild heating on gel properties and its relationship to denaturation of sausage protein. The results showed that, compared with samples treated by heating only (50 or 60 °C, 15 min), DPCD combined with mild heating (10 MPa, 50 or 60 °C, 15 min) increased the hardness, springiness and weight loss, meanwhile decreased the redness of the sausages. The DPCD treatments decreased the protein solubility which related to color, pH, weight loss, hardness and springiness significantly. The secondary structures change of myosin was observed, which induced the denaturation of myosin after DPCD combined with mild heating treatment. Actin denaturation depended on temperature and treatment time (more than 60 °C and 45 min) of DPCD. This study revealed DPCD combined with mild heating changed the structure of protein, cause protein denaturation and then induced gel formation of sausages.Practical ApplicationsGel property is one of the most functional characteristics of sausages, meatballs and other food produced by minced meat. People have tried different methods, for example adding salts and using high pressure, to improve gel property, water‐holding capacity, fat retention and reduce weight loss. In this study, DPCD combined with mild heating induced denser gel and cooked like appearance of the sausages compared with the samples treated by mild heating only. The results showed that DPCD treatment changed the processing property of minced mutton and can be used as a potential way to produce better gel meat products under low temperature.

In situ Raman quantification of the dissolution kinetics of carbon dioxide in liquid solutions during a dense phase and ultrasound treatment for the inactivation of Saccharomyces cerevisiae

In this work, a Raman based optical approach is presented that enables remote, real time and in situ quantification of the amount of carbon dioxide (CO2) dissolved in distilled water and coconut water during a dense phase carbon dioxide (DPCD) and a combined dense phase carbon dioxide and ultrasound (DPCD+US) pasteurization.CO2 dissolution kinetics were measured in an optically accessible high pressure cell at different temperatures (25, 35, 40°C) and pressures (8 and 12MPa). Two different mixing devices (mechanical and magnetic) during DPCD treatment, and different ultrasound powers (10, 20, 30W) during the DPCD+US treatment were applied. The dissolution data were then related with the inactivation ratio of Saccharomyces cerevisiae inoculated into the solutions. The results demonstrated that an increase of pressure or time during DPCD treatment enhances the amount of CO2 dissolved into the liquid, leading to a higher inactivation degree; the same trend was observed when the temperature was increased, although in this latter case, the amount of dissolved CO2 decreased. The increase of pressure during a combined DPCD+US treatment led to a higher amount of dissolved CO2, which positively influenced the microbial inactivation while no effect was obtained increasing the ultrasound power. Concerning the effect of the mixing devices, the mechanical stirrer was the one that enhanced the pasteurization efficiency as it influenced CO2 dissolution kinetics and, consequently, the microbial inactivation ratio. The composition of the liquid solutions also influenced the amount of dissolved CO2 but no correlations were found with S. cerevisiae inactivation.

Kinetics of “Laba” garlic greening and its physiochemical properties treated by Dense Phase Carbon Dioxide

The production of Chinese traditional and popular “Laba” garlic is limited to its homemade method. In this investigation, the technology of Dense Phase Carbon Dioxide (DPCD) was employed to produce this product for the first time. The greening, physiochemical properties and sensory quality of “Laba” garlic processed by this method were analyzed, respectively. Absorbance changes at 590 nm and color indices including L*, a*, b* and H° consistently showed that DPCD had significant effect on garlic greening. Changes of absorbance at 7, 10, 13 MPa (55 °C) and at 45, 55 °C (10 MPa) were well fitted to a zero-order kinetic model. Analysis of physiochemical and sensory properties comparing “Laba” garlic processed by the traditional method and DPCD treatment were performed. Results showed that vinegar pickling for 24 h after DPCD treatment significantly increased the consumers' acceptance of color, flavor and taste. This investigation illustrated that DPCD treatment greatly accelerated the greening reaction of “Laba” garlic and shortened its processing time. This treatment could become an alternative to the longer traditional method.

Effects of Dense Phase-CO&lt;sub&gt;2&lt;/sub&gt; Treatments on Micro&amp;#64258;ora, Enzymes and Browning of Chinese Winter Jujube Juice

Chinese winter jujube juice was treated with Dense Phase Carbon Dioxide (DPCD) to inactivate microorganisms, Polyphenoloxidase (PPO) activity, Peroxidase (POD) activity and control browing. The effect of varying pressures (5 to 30 MPa) and different treatment time (0 to 50 min) on the amount of natural microorganisms, PPO activity, POD activity and browning degree were measured. After experiment, the inactivation of natural microorganisms, PPO activity and POD activity exposed to DPCD were significantly increased with increasing pressure. Treated jujube juice had lower browning degree than untreated jujube juice. The experimental results showed that the DPCD treatment can be regarded as a good pretreatment means for winter jujube juice processing.

Volatile Composition and Aroma Activity of Guava Puree Before and After Thermal and Dense Phase Carbon Dioxide Treatments

Volatiles from initially frozen, dense phase carbon dioxide (DPCD)- and thermally treated guava purees were isolated by solid phase microextraction (SPME), chromatographically separated and identified using a combination of gas chromatography-mass spectrometry (GC-MS), GC-olfactometry (GC-O), and GC-pulsed flame photometric detector (GC-PFPD, sulfur mode). Fifty-eight volatiles were identified using GC-MS consisting of: 6 aldehydes, 2 acids, 15 alcohols, 6 ketones, 21 esters, and 8 terpenes. Eleven volatiles were newly identified in guava puree. Hexanal was the most abundant volatile in all 3 types of guava puree. Ten sulfur compounds were identified using GC-PFPD of which 3 possessed aroma activity and 3 were not previously reported in guava puree. Both treatments profoundly reduced total sulfur peak areas and produced different peak patterns compared to control. Thermal treatment reduced total sulfur peak area 47.9% compared to a loss of 34.7% with DPCD treatment. Twenty-six volatiles possessed aroma activity. (Z)-3-Hexenyl hexanoate was the major contributor to the aroma of the freshly thawed and DPCD-treated guava puree. DPCD treatment reduced total MS ion chromatogram (MS TIC) peak area 35% but produced a GC-O aroma profile very similar to control. Whereas thermal treatment reduced total TIC peak area only 8.7% compared to control but produced a 35% loss in total GC-O peak intensities.

Effects of the Application of Dense Phase Carbon Dioxide Treatments on Technological Parameters, Physicochemical and Textural Properties and Microbiological Quality of Lamb Sausages

The effects of different dense phase carbon dioxide (DPCD) treatments were evaluated on technological parameters, physicochemical and textural properties and microbiological quality of lamb sausages. Sausages were prepared using lamb meat (Longissimus dorsii, 68.6 % w/w), lamb fat (17.2 % w/w), water (12.9 % w/w) and NaCl (1.37 % w/w). Raw sausages were subjected to different CO2 pressures (10, 20 and 30 MPa) at 60 °C–30 min and treatment times (2, 14 and 25 min) at 55 °C–10 MPa. Weight loss, pH and total expressible fluid increased significantly (p < 0.05) as pressure increased from 0 to 30 MPa. These parameters also increased significantly (p < 0.05) as treatment time increased (at 10 MPa). The increase in CO2 pressure and treatment time significantly (p < 0.05) modified internal and surface color parameters. Lightness and b* values increased, whereas redness (a*) decreased. Also, the increase in CO2 pressure and treatment time significantly (p < 0.05) increased Warner–Bratzler shear force and textural parameters values. DPCD treatments may modify meat proteins, which may lead to weak interactions among proteins and formation of gel-like structures. Regarding microbial inactivation, the highest reductions in microbiological counts (2 Log CFU g−1) were obtained applying a CO2 pressure of 20 MPa at 60 °C for 30 min.

Effects of dense phase carbon dioxide and heat treatment on shrimp(Litopenaeus vannamei)meat qualities

Dense phase carbon dioxide(DPCD) is a promising non-thermal processing technology that affects microorganisms and enzymes through molecular effects of CO2 under pressures below 50MPa and temperature below 60℃. DPCD could affect food physical,nutritional,sensory qualities. In these experiments,compared with fresh shrimp( Litopenaeus vannamei),the effects of dense phase carbon dioxide(DPCD) and heat treatment on the nutrient components,mass loss,pH value,water-holding capacity, texture,protein and flavor components of shrimp meat were investigated. The results were as follows: compared with fresh shrimp,the water and crude fat content of shrimp meat treated by DPCD decreased significantly(P0.05) and the crude protein content of that had no significant change(P0.05),while the crude protein and fat content of shrimp meat treated by heat decreased significantly(P0.05); the mass loss of shrimp meat treated by DPCD was 16.02%±1.90%,but DPCD had no significant effect on pH value of shrimp meat(P 0.05); DPCD and heat treatment could induce shrimp protein denaturation,which caused water holding capacity of shrimp meat decreased significantly(P0.05),from(84.79±5.25)g/100g to(65.18±2.06)g/100g and( 65.58±2.08)g/100g respectively; DPCD treatment has no significant effect on hardness of shrimp meat( P0 05),while heat treatment caused hardness of shrimp meat to increased significantly(P0.05),from(3.48±0.49)N to(7.37±0.76)N; DPCD and heat treatment caused springiness of shrimp meat to decrease significantly(P0.05),from 0.88±0.08 to 0.71±0.03 and 0.78±0.03 respectively; except for betaine,PO3-4 and Cl-,the contents of other taste-active components(free amino acids,ATP related compounds,organic acid,and glycogen etc.) had no significant difference(P0.05) between DPCD treated and fresh shrimp,but heat treatment led to significant loss of shrimp meat taste-active components(P0.05). These results indicated that negative effects of DPCD treatment on shrimp meat qualities were less than those of heat treatment.

Effect of Dense Phase Carbon Dioxide on Inactivation of Polyphenol Oxidase and Peroxidase in Hami Melon Juice

Inactivation of polyphenol oxidase (PPO) and peroxidase (POD) in hami melon juice by treatment with dense phase carbon dioxide (DPCD) was investigated. DPCD treatment (60min, 35MPa 65°C), caused 79% and 81% loss in PPO and POD activities, respectively. The inactivation dynamics followed the first-order reaction kinetics. Higher pressures or temperatures resulted in higher inactivation constants. The treatment time needed for 90% inactivation and the activation energies for PPO and POD decreased in the presence of DPCD, compared with a 65°C thermal treatment. Pressure sensitivity at 65°C was also investigated. The results proved that DPCD was effective for inducing enzyme inactivation in hami melon juice.