Effect of vacuum-steam-vacuum treatment on microbial quality of whole and fresh-cut cantaloupe

Minimally processed fruits and vegetables have a limited shelf life because of deterioration caused by spoilage microflora and physiological processes. Cutting may increase microbial spoilage of fruits through transfer of microflora on the outer surfaces to the interior tissue. The objectives of this study were to use the vacuum-steam-vacuum (VSV) process to reduce indigenous spoilage microflora on the surface of cantaloupes and to investigate the effects of such treatments on transfer of spoilage microflora from the cantaloupe surface to the fresh-cut melon during rind removal and cutting. Whole cantaloupes were treated in the VSV processor, and fresh-cut pieces prepared from treated and control samples were stored at 5 and 10 degrees C for up to 9 days. Presence and growth of mesophilic bacteria, yeasts and molds, and Pseudomonas spp. were determined in fresh-cut samples during storage. Texture and color (CIE L*, a*, and b*) also were measured during storage. VSV treatment resulted in a 1.0-log reduction of aerobic mesophilic bacteria, a 2.0-log reduction of yeasts and molds, and a 1.5-log reduction of Pseudomonas spp. on cantaloupe surfaces. VSV treatment significantly reduced transfer of yeasts and molds and Pseudomonas spp. from whole cantaloupe surface to fresh-cut pieces during preparation (P < 0.05). Texture and color of the fresh-cut pieces prepared from the VSV-treated whole melons were similar to those of the controls. The results of this study indicate that the use of the VSV process to reduce the surface populations of yeasts and molds and Pseudomonas spp. on whole cantaloupes will reduce subsequent transfer of these microbes to fresh-cut pieces and enhance the microbial quality of the fresh-cut product.     

Effect of hot water surface pasteurization of whole fruit on shelf life and quality of fresh-cut cantaloupe

ABSTRACT:  Cantaloupes are associated with recent outbreaks of foodborne illnesses and recalls. Therefore, new approaches are needed for sanitization of whole and cut fruit. In the present study, whole cantaloupes were submerged into water in the following 3 conditions: 10 °C water for 20 min (control), 20 ppm chlorine at 10 °C for 20 min, and 76 °C water for 3 min. Populations of microflora were measured on the rinds of the whole cantaloupes. Quality and microbial populations of fresh-cut cantaloupes prepared from whole fruit were analyzed after 1, 6, 8, 10, 13, 16, and 20 d of storage at 4 °C. The hot water significantly reduced both total plate count (TPC) and yeast and mold count on rind of whole fruits while chlorine or cold water wash did not result in a significant reduction of microbial population. Fresh-cut pieces prepared from hot water-treated cantaloupes had lower TPC than the other 2 treatments in the later storage periods (days 13 to 20) in 2 of 3 trials. The hot water treatment of whole fruits was inconsistent in reducing yeast and mold count of fresh-cut pieces. Soluble solids content, ascorbic acid content, fluid loss, and aroma and appearance scores were not consistently affected by either hot water or chlorine treatment. Our results suggested that hot water pasteurization of whole cantaloupes frequently resulted in lower TPCs of fresh-cut fruit during storage and did not negatively affect quality of fresh-cut cantaloupes.     

Effect of hydrogen peroxide treatment on microbial quality and appearance of whole and fresh-cut melons contaminated with Salmonella spp

The efficacy of hydrogen peroxide treatment on the inactivation of Salmonella spp. inoculated on the external surface of cantaloupe and honeydew melon was investigated. Salmonella was inoculated onto whole cantaloupe and honeydew melon to a final concentration of 4.65 log(10) CFU/cm(2) and 3.13 log(10) CFU/g, respectively. Inoculated whole melons stored at 5 degrees C for up to 7 days were washed with water, 2.5% and 5% hydrogen peroxide at day 0 and 5. Hydrogen peroxide (2.5% and 5%) treatments of whole melon for 5 min caused a 3 log(10) CFU/cm(2) reduction of the indigenous surface microflora and a 3.0 log(10) CFU/cm(2) reduction in Salmonella spp. on all melon surfaces. The efficacy of the hydrogen peroxide treatments was less when the interval between inoculation and treatment of cantaloupe exceeded 24 h. Unlike cantaloupe fresh-cut pieces, Salmonella was not recovered from fresh-cut pieces prepared from treated whole honeydew melon. Growth of Salmonella occurred in cantaloupe fresh-cut pieces stored at 10 or 20 degrees C, and by 2 weeks, levels reached approximately 1 log CFU/g. A rapid decline in appearance and overall acceptability was observed in fresh-cut pieces prepared from untreated whole cantaloupe. While Salmonella was recovered from fresh-cut pieces from and whole treated cantaloupe, sanitizing the surface of contaminated whole melons with hydrogen peroxide before and after cutting and storage of the fresh-cut pieces at 5 degrees C can enhance the microbial safety and acceptability rating for about 2 weeks after processing.     

食前热水处理提高鲜切黄瓜微生物安全性的研究

探讨食前热水处理能否有效杀灭鲜切黄瓜表面的单增李斯特菌和鼠伤寒沙门氏菌这两种食源性致病菌,同时又保持其新鲜度。实验首先根据热水处理后鲜切黄瓜的感官品质,筛选了其耐热条件,进一步研究了热处理对水中和鲜切黄瓜表面食源性致病菌降低的效果。结果表明,经60℃ 5min热水处理,鲜切黄瓜上的鼠伤寒沙门氏菌、单增李斯特菌数量从高起始染菌浓度5.42、5.16log CFU/g,降低到检测线(0.6log CFU/g)以下,鲜切黄瓜的抗氧化值降低、细胞膜透性有所提高,但其测定硬度变化不大,感官上仍鲜脆,仍具有较好食用价值。      

Effect of hydrogen peroxide on quality of fresh-cut tomato

ABSTRACT:  The effect of hydrogen peroxide (H₂O₂; 0, 0.1, 0.2, and 0.4 M) on selected nutritional quality of fresh-cut tomato was investigated. Microbial population of tomato slices stored at 10 °C and treated with H₂O₂ was lower than the control by 1-(0.2 and 0.4 M) and 5-log (0.4 M), 3 and 7 d after processing, respectively. Dipping fresh-cut tomato into H₂O₂ resulted in reduced phenolic and antioxidant levels after 7 d in storage by at least 5% and 20%, respectively, and produced an initial decline in vitamin C and lycopene. Change in color values in the H₂O₂ treatments were associated with reduced carotenoid content. Our results confirmed antimicrobial benefits of H₂O₂ but revealed a compromise in antioxidant and carotenoid contents of fresh-cut tomatoes.     

Effect of oxygen on aroma volatiles and quality of fresh-cut cantaloupe and honeydew melons

Cantaloupe and honeydew melon cultivars were processed and stored under a high oxygen passive modified atmosphere packaging (MAP) or reduced oxygen controlled atmosphere (CA; 5 kPa O₂ + 10 kPa CO₂ and balance N₂) for 14 days at 5 °C. Atmosphere did not affect softening rate or soluble solids content and had a negligible effect on colour. Volatile compounds known as flavour-important in melons were extracted using stir bar sorptive extraction (SBSE) and quantified via GC–MS. Acetate esters increased more in MAP than in CA. Non-acetate esters increased markedly in both cultivars and storage types. Alcohols were more abundant in honeydew than in cantaloupe. Aldehydes decreased during storage in both cultivars and storage types. Lower O₂ availability under CA conditions likely suppressed some of the esters relevant to the aroma of fresh-cut melon. Results suggest that package O₂ levels are more important in determining aroma than other quality attributes of fresh-cut melon, and high O₂ levels may be required to reveal desirable aroma compounds.     

热处理对鲜切鸡毛菜品质的影响

以鲜切鸡毛菜为原料,研究不同温度(40、45、50℃)的热水处理5min对其品质的影响。结果表明:45℃热水处理5min对贮藏过程中鲜切鸡毛菜品质的保持效果最好,它维持了鲜切鸡毛菜较高的水分含量,延缓了叶绿素的降解,使鸡毛菜保持良好的外观,减缓了VC的降解,抑制了POD酶活,对可溶性糖含量有一定的保持作用。      

壳聚糖-柠檬烯涂膜对鲜切哈密瓜贮藏品质的影响

目的 探究壳聚糖-柠檬烯涂膜对鲜切哈密瓜贮藏品质的影响。方法 以无菌蒸馏水和2%壳聚糖涂膜处理鲜切哈密瓜作为对照组,用2%壳聚糖复配0.1%柠檬烯涂膜处理鲜切哈密瓜作为实验组,在贮藏第0、1、3、5、7 d对鲜切哈密瓜的感官、硬度、呼吸强度、可溶性固形物含量、色差、维生素C含量、多酚氧化酶(polyphenol oxidase, PPO)活性、过氧化物酶(peroxidase, POD)活性、过氧化氢酶(catalase, CAT)活性、超氧化物歧化酶(superoxide dismutase, SOD)活性及菌落总数进行测定。结果 2%壳聚糖复配0.1%柠檬烯涂膜显著(P<0.05)减缓了鲜切哈密瓜果肉软化,可溶性固形物和维生素C含量的下降及色差值L^*、a^*、b^*的改变;抑制了鲜切哈密瓜的呼吸强度、PPO和POD活性,增强了SOD和CAT活性,并抑制了菌落的生长,有利于鲜切哈密瓜感官品质的维持。结论 2%壳聚糖复配0.1%柠檬烯涂膜处理鲜切哈密瓜可以降低鲜切哈密瓜贮藏期间的营养物质损耗,减缓果肉的衰老变质,较好地...     

Reduction by gaseous ozone of Salmonella and microbial flora associated with fresh-cut cantaloupe

This research investigates the efficacy of gaseous ozone, applied under partial vacuum in a controlled reaction chamber, for the elimination of Salmonella inoculated on melon rind. The performance of high dose, short duration treatment with gaseous ozone, in this pilot system, on the microbial and sensory quality of fresh-cut cantaloupes was also evaluated. Gaseous ozone (10,000 ppm for 30 min under vacuum) reduced viable, recoverable Salmonella from inoculated physiologically mature non-ripe and ripe melons with a maximum reduction of 4.2 and 2.8 log CFU/rind-disk (12.6 cm(2)), respectively. The efficacy of ozone exposure was influenced by carrier matrix. Salmonella adhering to cantaloupe was more resistant to ozone treatment when suspended in skim-milk powder before aqueous inoculation to the rind. This indicated that organic matter interferes with the contact efficiency and resultant antimicrobial activity of gaseous ozone applied as a surface disinfectant. Conversely, in the absence of an organic carrier, Salmonella viability loss was greater on dry exocarp surfaces than in the wetted surfaces, during ozone treatment, achieving reductions of 2.8 and 1.4 initial log CFU/rind-disk, respectively. Gaseous ozone treatment of 5000 and 20,000 ppm for 30 min reduced total coliforms, Pseudomonas fluorescens, yeast and lactic acid bacteria recovery from fresh-cut cantaloupe. A dose Ct-value (concentration x exposure time) of 600,000 ppm min achieved maximal log CFU/melon-cube reduction, under the test conditions. Finally, fresh-cut cantaloupe treated with gaseous ozone, maintained an acceptable visual quality, aroma and firmness during 7-day storage at 5 degrees C. Conclusions derived from this study illustrate that gaseous ozone is an effective option to risk reduction and spoilage control of fresh and fresh-cut melon. Moreover, depending on the timing of contamination and post-contamination conditions, rapid drying combined with gaseous ozone exposure may be successful as combined or sequential disinfection steps to minimize persistence of Salmonella on the surface of cantaloupe melons and transference during fresh-cut processing of home preparation. Based on these results, greater efficacy would be anticipated with mature but non-ripe melons while ripe tissues reduce the efficacy of these gaseous ozone treatments, potentially by oxidative reaction with soluble refractive solids.     

Effect of hot water treatments on the safety and quality of Fusarium-infected malting barley

Utilization of Fusarium-infected barley for malting may lead to mycotoxin contamination of malt and decreased malt quality. Hot water treatments may prevent or reduce safety and quality defects and allow use of otherwise good quality barley. We evaluated hot water treatments for preventing Fusarium growth and mycotoxin production while maintaining barley-malt characteristics. Four barley lots with varying deoxynivalenol (DON) concentrations were hot water-treated at 45 or 50 degrees C for 0, 1, 5, 12, and 20 min. Treated barley was malted in a pilot-scale malting unit. Barley and malt were analyzed for Fusarium infection (FI), germinative energy (GE), aerobic plate count (APC), mold and yeast count (MYC), and DON. Malt quality parameters included malt extract, soluble protein, wort color, wort viscosity, free amino nitrogen, alpha-amylase, and diastatic power. Significant decreases in FI occurred within 1 min at both 45 degrees C (41-66%) and 50 degrees C (51-69%) in all barley samples. Significant reductions in APC (1.0-1.8 log) and MYC (1.7-1.8 log) in barley were observed after 5 min at both temperatures. The largest reductions for DON were observed in malts prepared from barley treated with hot water at 45 degrees C (79-93%) and 50 degrees C (84-88%) for 20 min. GE and most of the malt quality parameters were only affected when barley was treated at 50 degrees C for 12 and 20 min. The results suggest that hot water treatments may offer the potential for treating mildly FHB infected malting barley.     

Effect of gaseous ozone and hot water on microbial and sensory quality of cantaloupe and potential transference of Escherichia coli O157:H7 during cutting

The effect of gaseous ozone and hot water, alone or in combination, on the sensory and microbial quality of cantaloupe melon was investigated. Escherichia coli O157:H7 transmission from the rind to edible melon flesh during cutting practices was also investigated. Four different treatments consisting of hot water (75 degrees C, 1min), gaseous ozone (10,000ppm, 30min), gaseous ozone supplied by carbon monoxide gas and the combination of hot water and gaseous ozone were evaluated. Sensory quality and growth evolution of aerobic mesophilic and psychrotrophic bacteria, coliforms and molds were studied. In general, hot water, gaseous ozone, and the combination of hot water and gaseous ozone were effective in reducing total microbial population. The combination of hot water and gaseous ozone was the most effective treatment to control microbial growth achieving 3.8, 5.1, 2.2 and 2.3log reductions for mesophilic and psychrotrophic bacteria, molds and coliforms, respectively. However no significant differences were observed between gaseous ozone and gaseous ozone supplied by with carbon monoxide gas. There was no evidence of damage in melons treated with hot water, ozone or their combination and they maintained initial texture and aroma. Therefore, the combination of hot water and gaseous ozone may be an efficient and promising treatment for controlling microbial growth and maintaining sensory quality of melons.     

Effects of plasma-activated water on microbial growth and storage quality of fresh-cut apple

Fresh-cut ‘Fuji’ apples were immersed for 5 min in plasma-activated water (PAW) generated, by plasma generated with sinusoidal voltages at 7.0 kHz with amplitudes of 6 kV, 8 kV, and 10 kV, designated PAW-6, PAW-8, and PAW-10, respectively. The control group was soaked in distilled water for 5 min instead of PAW. The results indicated that the growth of bacteria, molds, and yeasts was inhibited by PAW treatments during storage at 4 ± 1 °C, especially the microbial inactivation with PAW-8, which was the most efficient. PAW-8 reduced the microbial counts by 1.05 log₁₀CFU g⁻¹, 0.64 log₁₀CFU g⁻¹, 1.04 log₁₀CFU g⁻¹ and 0.86 log₁₀CFU g⁻¹ for aerobic bacteria (aerobic plate counts), molds, yeasts and coliforms on day 12, respectively. In addition, the bacterial counts of fresh-cut apples treated with PAW were <5 log₁₀CFU g⁻¹, which did not exceed to the existing China Shanghai local standard (DB 31/2012–2013) during 12 days of storage. PAW treatments reduced superficial browning of fresh-cut apples without affecting their firmness and titratable acidity. In addition, no significant change was observed in antioxidant content and radical scavenging activity between the PAW-treated and control groups. It is suggested that PAW is a promising method for preservation of fresh-cut fruits and vegetables, which is usually beneficial to the quality maintenance of fresh-cut fruits and vegetables during storage.     

臭氧水处理对鲜切猕猴桃品质的影响

为了研究臭氧水对鲜切猕猴桃保鲜效果的影响,本实验以"海沃德"猕猴桃为试材,研究了不同浓度的臭氧水处理对鲜切猕猴桃可溶性固形物、可滴定酸、失重率、色差、抗坏血酸含量及细菌总数的影响。结果表明,0.7mg/L的臭氧水处理可以减缓鲜切猕猴桃贮藏期间可溶性固形物含量、色差值(L*值和a*值)和抗坏血酸含量的下降,并可以显著降低鲜切猕猴桃表面的细菌总数,在贮藏14d时细菌总数保持在106CFU/g以内,可以满足鲜切果蔬对微生物安全性的要求。然而,不同浓度臭氧水处理对鲜切猕猴桃的失重率和可滴定酸含量没有显著影响。实验结果表明,采用浓度为0.7mg/L的臭氧水浸渍鲜切猕猴桃5min,并于4℃条件贮藏,可使鲜切猕猴桃的货架期由10d(对照组)延长至14d。     

臭氧水处理对鲜切猕猴桃品质的影响

为了研究臭氧水对鲜切猕猴桃保鲜效果的影响,本实验以\     

中低温蒸汽处理对鲜切胡萝卜片减菌效果及其品质的影响

以鲜切胡萝卜片为研究对象,采用中低温蒸汽(50～100℃)进行减菌处理,分析了蒸汽处理过程中鲜切胡萝卜片品质指标的变化。结果表明,鲜切胡萝卜片的菌落总数、水分、类胡萝卜素、硬度、色泽等指标均随处理温度及时间的增加而显著减少(P<0.05)。采用低温蒸汽(50～70℃)处理600s,对胡萝卜片的减菌效果明显,且失水率小于5%,类胡萝卜素保留高于85%,对蔬菜的硬度和色泽影响较小。而经中温蒸汽(80～100℃)及传统的沸水热烫处理后的胡萝卜片,其品质质地明显降低。因此,低温蒸汽减菌处理能有效降低胡萝卜片中的菌落总数,并可最大程度保护其品质质地。     

采后热水和乙醇处理对枸杞鲜果腐烂的控制及品质的影响

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Combination of hot-water surface pasteurization of whole fruit and low-dose gamma irradiation of fresh-cut cantaloupe

Improvements in methods for disinfecting fresh-cut cantaloupe could reduce spoilage losses and reduce the risk of foodborne illness from human pathogen contamination. The objective of this study was to investigate the feasibility of using hot-water treatment in combination with low-dose irradiation to reduce native microbial populations while maintaining the quality of fresh-cut cantaloupe. Whole cantaloupes were washed in tap water at 20 or 76 degrees C for 3 min. Fresh-cut cantaloupe cubes, prepared from the washed fruit, were then packaged in clamshell containers, and half the samples were exposed to 0.5 kGy of gamma radiation. Native microflora populations and sensory qualities were evaluated during the subsequent 7 days of storage at 4 degrees C. The hot-water surface pasteurization reduced the microflora population by 3.3 log on the surface of whole fruits, resulting in a lower microbial load on the fresh-cut cubes compared with cubes cut from fruit treated with cold water. Irradiation of cubes prepared from untreated fruit to an absorbed dose of 0.5 kGy achieved a low microbial load similar to that of cubes prepared from hot-water-treated fruit. The combination of the two treatments was able to further reduce the microflora population. During storage, the headspace atmosphere of the packages was not significantly influenced by any of the treatments. Color, titratable acidity, pH, ascorbic acid, firmness, and drip loss were not consistently affected by treatment with irradiation, hot water, or the combination of the two. Cubes prepared from hot-water-treated whole fruit had slightly lower soluble solids content. The combination of hot-water pasteurization of whole cantaloupe and low-dose irradiation of packaged fresh-cut melon can reduce the population of native microflora while maintaining the quality of this product.     

Effect of gamma irradiation on microbial growth and sensory quality of fresh-cut lettuce

Fresh-cut lettuce was irradiated and microbiological and sensory quality was examined during storage at 4 degrees C. Experimental results showed that the number of aerobic mesophilic bacteria on fresh-cut lettuce irradiated with 1.0 kGy was reduced by 2.35 logs and sensory quality was maintained best during storage for 8 days at 4 degrees C. It was indicated that Gompertz model could predict the bacterial number on fresh-cut lettuce if the initial level was known.     

臭氧水对鲜切胡萝卜贮藏品质的影响

采用不同浓度(10~50 mg/L)的臭氧水对鲜切胡萝卜进行处理,测定了在4℃贮藏过程中样品的理化指标、菌落总数和感官品质。结果表明,40 mg/L臭氧水中处理10 min,可以有效地保持鲜切胡萝卜的硬度和脆度,降低失重率和延缓V_C的降解,同时能延缓表面微生物的生长和繁殖。