首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 765 毫秒
1.
In this study, the effect of high pressure homogenization (HPH) and dimethyl dicarbonate (DMDC) on microbial and nutrient qualities of mulberry juice was evaluated. Results showed that repeated HPH passes at 200 MPa or adding DMDC at 250 mg/L significantly inactivated the indigenous microorganisms in mulberry juice (P < 0.05), whereas some surviving microorganisms recovered to grow during storage of 4 °C. The combined treatment with 3 passes of HPH and 250 mg/L of DMDC (HPH‐DMDC) decreased the population of surviving indigenous microorganisms to the level attained by heat treatment at 95 °C for 1 min (HT) with no significant increase (P > 0.05) in the population of microorganisms during subsequent storage at 4 °C. Moreover, no significant changes (P > 0.05) in the physical attributes, including pH, TSS (oBrix), L*, a*, and b* values were observed in the samples treated by the HPH‐DMDC or by HT. Compared with HT, HPH‐DMDC treatment resulted in a higher degree of retention in total phenolics, and α‐glucosidase inhibitory activity, although the treatment led to higher losses in cyanidin 3‐glucoside, cyanidin 3‐rutinoside, and antioxidant capacity. Overall, HPH‐DMDC treatment can be a useful alternative to conventional thermal pasteurization of mulberry juice, considering its ability to inactive, and inhibit indigenous microorganisms.  相似文献   

2.
本文研究了二甲基二碳酸盐(DMDC)和Nisin处理对模拟果汁中肠膜状明串珠菌的杀菌效果及其细胞膜功能的影响。结果表明:DMDC联合Nisin作用于该菌时的部分杀菌浓度指数为0.38,小于0.50,两者之间具有很好的协同杀菌作用。扫描电镜分析发现该菌经DMDC和Nisin处理后其细胞形态没有发生明显变化。该菌经DMDC处理后仅有个别菌体细胞的膜通透性出现增加,而该菌经Nisin处理后,约7%菌体细胞的膜通透性增加。Nisin处理虽能改变该菌的细胞膜通透性,增加胞外极性物质的摄入,但并不能明显促进胞内物质的流失,高浓度的DMDC处理能导致该菌溶液的紫外吸收值增加约60%。DMDC和Nisin两者对该菌细胞内物质的流失、细胞膜的通透性的增加和胞内p H的下降没有相互促进作用,但DMDC和Nisin的联合作用能促进该菌细胞内脱氢酶的进一步失活。  相似文献   

3.
ABSTRACT: This study was to develop an antimicrobial bottle coating method to reduce the risk of outbreaks of human listeriosis caused by contaminated liquid foods. Liquid egg white and skim milk were inoculated with Listeria monocytogenes Scott A and stored in glass jars that were coated with a mixture of polylactic acid (PLA) polymer and nisin. The efficacy of PLA per nisin coating in inactivating L. monocytogenes was investigated at 10 and 4 °C. The pathogen grew well in skim milk without PLA/nisin coating treatments, reaching 8 log CFU/mL after 10 d and then remained constant up to 42 d at 10 °C. The growth of Listeria at 4 °C was slower than that at 10 °C, taking 21 d to obtain 8 log CFU/mL. At both storage temperatures, the PLA coating with 250 mg nisin completely inactivated the cells of L. monocytogenes after 3 d and throughout the 42-d storage period. In liquid egg white, Listeria cells in control and PLA coating without nisin samples declined 1 log CFU/mL during the first 6 d at 10 °C and during 28 d at 4 °C, and then increased to 8 or 5.5 log CFU/mL. The treatment of PLA coating with 250 mg nisin rapidly reduced the cell numbers of Listeria in liquid egg white to undetectable levels after 1 d, then remained undetectable throughout the 48 d storage period at 10 °C and the 70 d storage period at 4 °C. These data suggested that the PLA/nisin coating treatments effectively inactivated the cells of L. monocytogenes in liquid egg white and skim milk samples at both 10 and 4 °C. This study demonstrated the commercial potential of applying the antimicrobial bottle coating method to milk, liquid eggs, and possibly other fluid products.  相似文献   

4.
ABSTRACT: Sulfur dioxide (SO2) at 0, 10, 25, and 50 mg/L and/or dimethyldicarbonate (DMDC) at 0, 50, 100, and 200 mg/L at different pH levels (3.0, 3.2, 3.4, and 3.6) in juice and semi-sweet wine were evaluated by monitoring yeast growth and visible fermentation at 20 °C after excessive yeast contamination (500 to 700 colony forming units/mL), using Saccharomyces bayanus. The treatments with the least preservatives that prevented yeast growth and visible fermentation at all pH levels in juice were 50 mg/L SO2+ 100 mg/L DMDC and in wine were 10 mg/L SO2+ 50 mg/L DMDC. DMDC and minimal SO2 levels prevented fermentation in juice and semi-sweet wine with excessive yeast contamination.  相似文献   

5.
Li H  Zhao L  Wu J  Zhang Y  Liao X 《Food microbiology》2012,30(1):139-145
The individual and combined effects of high-pressure carbon dioxide (HPCD), mild heat (MH) and nisin (200 ppm) on the inactivation of natural microorganisms, including aerobic bacteria (AB), yeasts and molds (Y&;M), in litchi juice were evaluated. The samples were treated at a pressure of 10 MPa and temperatures of 32, 42 or 52 °C for 5, 10, 15, 20, 25 or 30 min. Temperature played a prominent role in the inactivation of both AB and Y&;M when combined with HPCD, particularly for AB at 52 °C and Y&;M at temperatures ≥42 °C. Nisin increased the susceptibility of AB to the combined treatment of HPCD and MH (HPCD + MH). A reduction of 4.19 log cycles was achieved by HPCD + MH at 52 °C for 15 min, and complete inactivation of AB was obtained by combination of HPCD, MH and nisin (HPCD + MH + nisin). No significant effect of nisin was found on the inactivation of Y&;M.  相似文献   

6.
Sulfur dioxide (SO2), sorbic acid (SB), dimethyldicarbonate (DMDC), and their combinations were studied for suppression of fermentation at 21°C or 31°C in grape juice inoculated with 2, 200, or 20,000 colony forming units (CFU)/mL of yeast. The other preservatives did not suppress as well as DMDC. The DMDC (0.8 mM) prevented fermentation at all inoculation levels at both temperatures, except that inoculated with 20,000 CFU/mL at 21°C. The 0.8-mM level of SO2+DMDC. and SB + DMDC orevented fermentation in samoles inoculated with 2 or 200 CFU/mL at 31°C. Storage at 31°C decreased effectiveness of SO2, SB, and SO2+ SB but increased effectiveness of DMDC, SO2+ DMDC, and SB+DMDC (0.8 mM level).  相似文献   

7.
Keeping quality of fresh orange juice is highly dependent on pectinolytic enzyme activity and the growth of spoilage microorganisms. The inactivation kinetics of indigenous pectin methylesterase (PME) and of the two more pressure resistant species of spoilage lactic acid bacteria (LAB) Lactobacillus plantarum and L. brevis in freshly squeezed Valencia orange juice under high hydrostatic pressure (100–500 MPa) combined with moderate temperature (20–40 °C) was investigated. PME inactivation followed first order kinetics with a residual PME activity (15%) at all pressure–temperature combinations used. The values of activation energy and activation volume were estimated at each pressure and at each temperature, respectively. Values of 90 kJ/mol and ?30 mL/mol at reference pressure of 300 MPa and reference temperature of 35 °C were estimated respectively. The corresponding zT and zP values of LAB inactivation were also estimated at all conditions tested. Values of 19.5 °C and 95 MPa at reference pressure of 300 MPa and reference temperature of 30 °C were estimated respectively for L. plantarum, while the corresponding values for L. brevis were 40 °C and 82 MPa, respectively, at the same reference conditions. Pressure and temperature were found to act synergistically both for PME and LAB inactivation. The PME and LAB inactivation rate constants were expressed as functions of the temperature and pressure process conditions. These functions allow the determination of the pressure/temperature conditions that achieve the target enzyme and microbial inactivation at a selected processing time. The process conditions of 350 MPa at 35 °C for 2 min are proposed as effective for Valencia orange juice cold pasteurisation.  相似文献   

8.
Abstract: Antimicrobial activities of chitosan against lactic acid bacteria were studied to apply for controlling dongchimi (whole-radish juicy kimchi) fermentation to prevent over-ripening. Antimicrobial activity of chitosan against lactic acid bacteria such as Leuconostoc mesenteroides and Lactobacillus plantarum was assayed at 10, 20, 30, and 40 mg/L concentration in the medium. The addition of 40 mg/L of the chitosan prepared at 140 °C for 10 min showed strong inhibitory effect on the growth of L. mesenteroides and L. plantarum. The effects of addition of chitosan to dongchimi have also been studied during fermentation at different temperatures of 4, 10, and 20 °C. Addition of chitosan decreased markedly viable cell counts of lactic acid bacteria such as Leuconostoc spp. and Lactobacillus spp. at the initial stage. Subsequently the lactic acid bacteria recovered the growth to the same level as non-chitosan treated dongchimi. During the dongchimi fermentation, the addition of chitosan at larger quantity up to 1000 mg/L (CS1000) prolonged the palatable fermentation period. Addition of chitosan in the dongchimi seemed to inhibit the growth of lactic acid bacteria, thereby lowering the acid content. It, therefore, caused the shelf life to be extended and resulted in a prolonged palatable period for the dongchimi.  相似文献   

9.
Antimicrobial edible films based on sodium caseinate, glycerol, and 2 food preservatives (nisin or natamycin) were prepared by classical thermomechanical processes. Food preservatives were compounded (at 65 °C for 2.5 min) with sodium caseinate in a twin‐screw extruder. Anti‐Listeria activity assays revealed a partial inactivation of nisin following compounding. Thermoplastic pellets containing food preservatives were then used to manufacture films either by blown‐film extrusion process or by heat‐press. After 24 h of incubation on agar plates, the diameters of K. rhizophila growth inhibition zones around nisin‐incorporated films prepared by solution casting (control), extrusion blowing or heat pressing at 80 °C for 7 min of nisin‐containing pellets were 15.5 ± 0.9, 9.8 ± 0.2, and 8.6 ± 1.0 mm, respectively. Since heat‐pressing for 7 min at 80 °C of nisin‐incorporated pellets did not further inactivate nisin, this indicates that nisin inactivation during extrusion‐blowing was limited. Moreover, the lower diameter of the K. rhizophila growth inhibition zone around films prepared with nisin‐containing pellets compared to that observed around films directly prepared by solution casting confirms that nisin inactivation mainly occurred during the compounding step. Natamycin‐containing thermoplastic films inhibited Aspergillus niger growth; however, by contrast with nisin‐containing films, heat‐pressed films had higher inhibition zone diameters than blown films, therefore suggesting a partial inactivation of natamycin during extrusion‐blowing.  相似文献   

10.
This study explored the effectiveness of high pressure (200–500 MPa) alone or in combination with mild thermal treatments (35 and 50 °C) and nisin (25 and 50-ppm) on the inactivation of L. innocua and E. coli in carrot juice. Processing at 500 MPa at 20 °C for 2 min without nisin resulted in 4- and 5-log CFU/mL reduction of L. innocua and E. coli, respectively while incorporating 25-ppm nisin at same pressure and temperature rendered 7-log CFU/mL reduction. There was synergism between high pressure, nisin, and heat in all treatments to inactivate both microorganisms. After a 28-d of refrigerated storage, total plate counts were <2-log CFU/mL in carrot juice treated with combination of 300 MPa and 25-ppm nisin at 35 °C. All combinations resulted in less intense use of pressure, i.e. more energy efficient, cost effective processes while attaining high quality juices. The results of this study suggest that by using selected combinations of high pressure, nisin and mild temperatures, safe, clean-label, high-quality juices can be produced.Industrial relevanceThe results from this study show a synergistic effect on the inactivation of L. innocua and E. coli in carrot juice from the combined application of HPP, nisin, and mild temperatures. By replacing the use of HPP alone by these combinations will allow the use of reduced pressures over shorter period of times to process low-acid juices, lowering energy requirements and increasing throughput. This study will aid the beverage processing industry in the development of clean label juice products with fresh-like quality attributes and using considerable less energy to conventional processing.  相似文献   

11.
In order to preserve a commercial dealcoholized red wine (DRW), a study with 4 preservatives and binary mixtures of them were performed against 2 native spoilage yeasts: Rhodotorula mucilaginosa and Saccharomyces cerevisiae. Minimal inhibitory concentration (MIC) and minimal fungicidal concentration (MFC) for potassium sorbate, sodium benzoate, sodium metabisulfite and dimethyl dicarbonate (DMDC) were evaluated in DRW stored at 25 °C. MICs of potassium sorbate and sodium metabisulfite were 250 and 60 mg/kg, respectively for both target strains. However for sodium benzoate, differences between yeasts were found; R. mucilaginosa was inhibited at 125 mg/kg, while S. cerevisiae at 250 mg/kg. Regarding MFC, differences between strains were only found for sodium metabisulfite obtaining a MFC of 500 mg/kg for R. mucilaginosa and a MFC of 250 mg/kg for S. cerevisiae. Potassium sorbate and sodium benzoate showed the MFC at 1000 mg/kg and DMDC at 200 mg/kg. Regarding the effect of binary mixtures the Fractional Fungicidal Concentration Index (FFCi) methodology showed that binary mixtures of 100 mg/kg DMDC/200 mg/kg potassium sorbate (FFCi = 0.7) and 50 mg/kg DMDC / 400 mg/kg sodium benzoate (FFCi = 0.65) have both synergistic effect against the 2 target strains. These binary mixtures can control the growth of spoilage yeasts in DRW without metabisulfite addition. The results of this work may be important in preserving the health of DRW consumers by eliminating the use of metabisulfite and reducing the risk of growth of R. mucilagosa, recently recognized as an emerging pathogen.  相似文献   

12.
Identifying equivalent processing conditions is critical for the relevant comparison of food quality attributes. This study investigates equivalent processes for at least 5-log reduction of Escherichia coli and Listeria innocua in pineapple juice–coconut milk (PC) blends by high-pressure processing (HPP), pulsed electric fields (PEF), and ultrasound (US) either alone or combined with other preservation factors (pH, nisin, and/or heat). The two blends (pH 4 and 5) and coconut milk (pH 7) as a reference were subjected to HPP at 300–600 MPa, 20°C for 0.5–30 min; PEF at an electric field strength of 10–21 kV/cm, 40°C for 24 µs; and US at 120 µm amplitude, 25 or 45°C for 6 or 10 min. At least a 5-log reduction of E. coli was achieved at pH 4 by HPP at 400 MPa, 20°C for 1 min; PEF at 21 kV/cm, 235 Hz, 40°C for 24 µs; and US at 120 µm, 45°C for 6 min. As L. innocua showed greater resistance, a synergistic lethal effect was provided at pH 4 by HPP with 75 ppm nisin at 600 MPa, 20°C for 5 min; PEF with 50 ppm nisin at 18 kV/cm, 588 Hz, 40°C for 24 µs; and US at 45°C, 120 µm for 10 min. The total soluble solids (11.2–12.4°Bx), acidity (0.47%–0.51% citric acid), pH (3.91–4.16), and viscosity (3.55 × 10−3–4.0 × 10−3 Pa s) were not significantly affected under the identified equivalent conditions. HPP was superior to PEF and US, achieving higher ascorbic acid retention and lower color difference in PC blend compared to the untreated sample.  相似文献   

13.
Listeria monocytogenes was subjected to ultra high hydrostatic pressure (UHHP) treatments from 200 to 700 MPa at 25 °C in broth, raw milk, peach juice and orange juice. Survivor curves showed that cell death increased as pressure increased. After 10 min pressure treatment at 400 MPa reductions of about 2.09 and 2.76 log CFU mL?1 in aerobic bacteria and L. monocytogenes, respectively, were produced in raw milk, this increased to 5.09 and 6.47 log CFU mL?1, respectively, at 600 MPa. Death of bacteria at UHHP treatment was greater in orange juice than peach juice, and in peach juice than milk. Listeria monocytogenes was more sensitive to increased pressure than increased pressurization time. Injury of L. monocytogenes occurred from 0 to 100%. Factors effecting the rate of microbial inactivation are: pressure, age of cell, composition of medium, and pressurization time. UHHP inactivation can be used to extend shelf life and increase food quality during storage, and may also contribute to inactivation of L. monocytogenes.  相似文献   

14.
The objective of this study was to evaluate the inhibitory effect of grape seed extract (GSE), green tea extract (GTE), nisin and their combinations (nisin with either GSE or GTE) against Listeria monocytogenes. The inhibitory effect of these natural compounds was evaluated in phosphate buffer solution (PBS) medium containing approximately 109 colony‐forming units (CFU/mL) of L. monocytogenes. The effectiveness of these compounds in a meat model system was evaluated by surface inoculation (approximately 106 CFU/g) of L. monocytogenes onto turkey frankfurters. The inoculated frankfurters were dipped into soy protein film‐forming solutions with and without the addition of antimicrobial agents (GSE 1% or GTE 1% or nisin 10000 IU or combinations). Samples were stored at either 4 °C or 10 °C. The inhibitory effects of edible coatings were evaluated on a weekly basis for 28 d. The greatest inhibitory effect was observed in the PBS medium containing GSE (1%) and nisin (10000 IU/mL), which caused a 9‐log cycle reduction of L. monocytogenes population after 3 h incubation at 37 °C. In the meat system, the L. monocytogenes population (7.1 CFU/g) was decreased by more than 2 log cycle after 28 d at 4 °C and 10 °C, in the samples containing nisin (10000 IU) combined with either GSE (1%) or GTE (1%). This research has demonstrated that the use of an edible film coating containing both nisin and natural extracts is a promising means of controlling the growth and recontamination of L. monocytogenes on ready‐to‐eat meat products.  相似文献   

15.
ABSTRACT: Inactivation of Escherichia coli O157:H7 and Salmonella in apple cider and orange juice treated with ozone in combination with antimicrobials was evaluated. E. coli O157:H7 or Salmonella was suspended in cider and orange juice, and ozone was pumped into juices (4°C) containing dimethyl dicarbonate (DMDC; 250 or 500 ppm) or hydrogen peroxide (300 or 600 ppm) for up to 90 min (study 1) or 60 min followed by 24-h storage at 4°C (study 2). Study 1: No combination of treatments resulted in a 5-log colony-forming units (CFU) /mL reduction of either pathogen. Study 2: All combinations of antimicrobials plus ozone treatments, followed by refrigerated storage, caused greater than a 5-log CFU/mL reduction, except ozone/DMDC (250 ppm) treatment in orange juice. Ozone treatment in combination with DMDC or hydrogen peroxide followed by refrigerated storage may provide an alternative to thermal pasteurization to meet the 5-log reduction standard in cider and orange juice.  相似文献   

16.
Inhibitory activity of reuterin (β-hydroxypropionaldehyde) combined with the antimicrobial peptide nisin or the lactoperoxidase system (LPOS) against food-borne Gram-negative pathogens in milk refrigerated at 4 and 8 °C was investigated. At 4 °C, reuterin (8 AU/ml) and LPOS were bactericidal against Salmonella enterica, Campylobacter jejuni, Aeromonas hydrophila and Yersinia enterocolitica, whereas the only effect recorded for nisin was a slight inhibition of Escherichia coli O157:H7. At 8 °C, reuterin was bactericidal against all the Gram-negative pathogens studied. Same results were attained with LPOS, except for its effect on Y. enterocolitica which was only bacteriostatic. The combination of reuterin with nisin did not enhance the antimicrobial effect of reuterin. A strong synergistic bactericidal activity of reuterin in combination with LPOS on E. coli O157:H7 and S. enterica was observed in milk at 4 °C, and against all the Gram-negative bacteria assayed in milk refrigerated at 8 °C. The application of both antimicrobials would be a useful means to inhibit pathogenic microorganisms, which may be present in milk due to postpasteurization contamination.  相似文献   

17.
The effect of dimethyldicarbonate (DMDC) on vegetative growth elements as well as ascospores of two strains of Byssochlamys fulva was investigated. Using apple juice as the suspending medium, vegetative growth was found to be sensitive to the compound at concentrations of 25 to 75 mg/l; temperature had a marked influence on lethality, with treatment at higher temperature being far more lethal than low temperature treatment; ascospores were highly resistant to the compound, with no evidence of any lethal effects being found even at the highest concentration used (1,000 mg/l). An inoculated pack study, designed to simulate the use of DMDC in fruit juices under practical conditions, was performed using commercially packaged apple juice or strawberry nectar as the suspending media. Packs, equilibrated to temperatures of 10 degrees C or 30 degrees C, were aseptically inoculated with low numbers of either vegetative elements or ascospores and were treated with varying levels of DMDC. Mould development was monitored over a four week period. Whereas vegetative growth was controlled at DMDC concentrations of 50 to 100 mg/l at a treatment temperature of 30 degrees C, ascospores displayed a great tolerance to the compound and survived exposure even in low numbers to high DMDC concentrations.  相似文献   

18.
Antimicrobial activities of nisin, tea polyphenols (TPs), and chitosan, and their combinations were evaluated against both Gram‐positive bacteria (GPB) and Gram‐negative bacteria (GNB) by the agar dilution method. Results showed that the MIC of nisin was 2.44 to 1250 mg/L for GPB and reached 5000 mg/L for GNB. The MICs of TPs and chitosan were 313 to 625 mg/L and 469 mg/L for GNB, and 156 to 5000 mg/L and 234 to 938 mg/L for GPB, respectively. These results indicated that TPs and chitosan exhibited inhibitory effects against both GPB and GNB, whereas nisin inhibited the growth of GPB only. Based on the orthogonal test of their MICs, and evaluation of preservative effect and sensory attributes in chilled mutton, the optimum combination was chosen as 0.625, 0.313, and 3.752 g/L for nisin, TPs, and chitosan, respectively. By using the optimum treatment, the shelf life of chilled mutton was extended from 6 to 18 d at 4 °C in the preservative film packages. These results indicate that the combination of nisin, TPs, and chitosan could be used as preservatives to efficiently inhibit the growth of spoilage microorganisms and pathogens in meat, thus improving the safety and shelf life of chilled mutton.  相似文献   

19.
Commercially produced samples of citrus molasses, unpasteurized orange juice and frozen concentrated orange juice were qualitatively assayed for lactic acid bacteria. Two species of Lactobacillus (L. fermentun and L. plantarum) and three species of Leuconostoc (Le. mesenteroides subsp. dextranicum, Le. mesenteroides subsp. mesenteroides and Le. paramesenteroides) were found. L. fermentum and Le. paramesenteroides have not previously been reported in citrus products.  相似文献   

20.
A total of fifty‐six strains of lactic acid bacteria isolated from Chinese sauerkraut juice from Shenyang were screened for glucansucrase production. Among them, strain DRP105 was detected to produce highest yield of glucansucrase in MRS broth, which was identified to be Leuconostoc mesenteroides. Based on Plackett–Burman Experiment, sucrose, sodium acetate and initial pH were found to be the most significant factors for glucansucrase production of L. mesenteroidesDRP105. Afterwards, effects of the three main factors on glucansucrase activity were further investigated by central composite design, and the optimum composition was sucrose 35.74 g L?1, sodium acetate 6.46 g L?1 and initial pH 5.90. Optimum results showed that glucansucrase activity was increased to 6.26 ± 0.09 U mL?1 in 24 h fermentation, 33.19% higher than before. Our study also suggested that Tween 80 and dextran have potential to improve glucansucrase stability at temperature (30 °C) higher than enzyme storage temperature in crude fermented broth.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号