Effects of Calcium Ascorbate and Ionizing Radiation on the Survival of Listeria monocytogenes and Product Quality of Fresh-cut 'Gala' Apples

The interactive effects of calcium ascorbate (CaA) and ionizing radiation on viability of Listeria monocytogenes inoculated in solutions and on ‘Gala’ apple slices were investigated. The D10 values (radiation doses that inactivate 90% of bacterial population) for L. monocytogenes inoculated in water, 3.5%, and 7.0% CaA solutions were 0.32, 0.61, and 0.58 kGy, respectively. The D₁₀ values of the pathogen on the surface of apple slices treated with water, 3.5%, and 7.0% CaA were 0.24, 0.32, and 0.32 kGy, respectively. To determine the impact of CaA and irradiation on quality of apple slices, apple slices treated with 0%, 3.5%, and 7.0% CaA were exposed to 1.6 kGy gamma radiation (a dose that produced a 5‐log reduction of L. monocytogenes) and stored under modified atmosphere at 4 °C for 14 d. CaA at levels of both 3.5% and 7.0% prevented the browning of the apple slices. The apple aroma intensity, however, decreased as the concentration of CaA increased. Irradiation at 1.6 kGy did not significantly affect color, soluble solid content, titratable acidity, or apple aroma intensity. The only negative effect of irradiation on apple slices appeared to be a loss of firmness. Our results suggest that CaA, used as an antibrowning agent, protected L. monocytogenes from radiation both in solution and on apple slices, but radiation at doses sufficient to inactivate 5‐log of the bacterium did not significantly influence product quality attributes except for the loss in firmness.     

抗坏血酸钙处理对鲜切鸭梨品质的影响

以新鲜鸭梨为原料,采用不同浓度的抗坏血酸钙溶液浸泡处理鲜切鸭梨,研究了其在4℃贮藏条件下的感官及理化品质变化。结果表明:抗坏血酸钙处理可抑制鲜切鸭梨的褐变,减弱其软化程度,减缓膜透性的增大及抑制多酚氧化酶的活性,保持鲜切鸭梨的外观品质和营养价值。     

一氧化氮缓释熏蒸处理对鲜切苹果片品质的影响

本文研究一氧化氮(nitric oxide,NO)气体缓释熏蒸处理对鲜切苹果片品质变化的影响。以红富士苹果为试材,将鲜切苹果片与NO供体二乙烯三胺一氧化氮聚合物(diethylenetriamine/nitric oxide,DETANO)、柠檬酸及玉米淀粉制成的NO气体缓释剂共置于密闭容器中,在4℃条件下贮藏。贮藏期间测定鲜切苹果片的表面明度(lightness,L*)值、果肉硬度、失重率、总酚含量、多酚氧化酶(polyphenoloxidase,PPO)活性、可溶性固形物含量、维生素C含量以及可滴定酸含量。结果表明:与对照组相比,NO气体缓释熏蒸处理能有效减轻鲜切苹果片的表面褐变、果肉软化和失重,显著抑制总酚含量的下降和PPO活性的升高,并保持可溶性固形物、维生素C和可滴定酸含量,延缓鲜切苹果片的品质劣变,为鲜切苹果片的贮藏保鲜提供了一种新方法。     

Effect of 1-Methylcyclopropene on the Quality of Fresh-cut Apple Slices

ABSTRACT: The objective of this project was to treat fresh-cut apple slices with the ethylene inhibitor 1-methylcyclopropene (1-MCP) to retard ethylene-induced deterioration and senescence and to prolong the shelf life of such products. Intact Braeburn and Pacific Rose apples were treated at different times with 1-MCP, cut, and stored at 0 °C. Samples were analyzed initially and then weekly for ethylene, respiration, flesh firmness, tissue color, titratable acidity, and soluble solids content during 5 wk of storage. 1-MCP treatment was effective in reducing ethylene production, respiration, and loss of firmness and color of slices when applied to whole apples directly after harvest. Total sugar and acidity levels were not affected significantly.     

Effects of Gamma Irradiation on the Texture of Minimally Processed Apple Slices

ABSTRACT: Fresh-cut apples with or without calcium treatments were irradiated at doses up to 5 kGy at 0.4 and 2 kGy.h^-1 dose rates with a Co⁶⁰ source in 0, 21, and 100% O₂ atmospheres. Firmness decreased as irradiation dose increased beyond a 0.34 kGy threshold. High dose rate initially resulted in less softening compared to low dose rate, but dose rate became insignificant upon storage. Irradiation atmosphere did not affect firmness. Softening of irradiated slices correlated positively with water-soluble pectin, and negatively with oxalate-soluble pectin content. Calcium prevented irradiation-induced softening of thin slices (3-4 mm thick), but was not effective with thicker wedges due to limited penetration.     

Quality of Minimally Processed Apple Slices from Selected Cultivars

Twelve cultivars were prepared as slices and stored 12 days at 2°C. Changes in respiration and quality factors were compared. Initial respiration rates among cultivars varied from 3.5 mL CO₂/kg/hr in Delicious to 7.6 mL CO₂/kg/hr in Monroe and decreased rapidly during the first 3 days. Idared, McIntosh, Delicious, and Rome showed relatively low respiration throughout storage. Firmness of slices during storage decreased gradually for 7 days and more rapidly thereafter. Empire, Golden Delicious, and Idared apples showed minimum changes in firmness. Change in color of slices was rapid during the first 3 days. Cortland. Emuire. Golden Delicious. New York 674. and Delicious showed least browning. Titratable acidity, pH, soluble solids, and weight changes during storage were small and varied by cultivar. NY674, Cortland, Golden Delicious, Empire, and Delicious showed more desirable attributes for minimal processing.     

壳聚糖涂膜对鲜切苹果贮藏品质的影响

为研究壳聚糖涂膜对鲜切苹果贮藏品质的影响,将鲜切寒富苹果分别用质量分数0.5%、1.0%、1.5%的壳聚糖浸泡3 min后沥干,用0.11 mm厚度的PE保鲜膜包装后置于4 ℃冷库中贮藏,每2 d测定与成熟衰老相关的生理生化指标。结果表明,适当质量分数的壳聚糖涂膜可保持苹果切块的感官品质、延缓营养物质下降、抑制微生物的繁殖,对鲜切苹果有较好的护色效果;壳聚糖涂膜也能较好地抑制多酚氧化酶活性,提高过氧化物酶活性。在研究的3 种质量分数中,1.0%壳聚糖处理对鲜切苹果的保鲜效果最好,能在4 ℃冷库12 d贮藏期中维持鲜切苹果的较好品质。     

Antibrowning and Antimicrobial Properties of Sodium Acid Sulfate in Apple Slices

ABSTRACT: There are few available compounds that can both control browning and enhance microbial safety of fresh‐cut fruits. In the present study, the antibrowning ability of sodium acid sulfate (SAS) on “Granny Smith” apple slices was first investigated in terms of optimum concentration and treatment time. In a separate experiment, the apple slices were treated with water or 3% of SAS, calcium ascorbate, citric acid, or acidified calcium sulfate for 5 min. Total plate count, color, firmness, and tissue damage were assessed during a 21‐d storage at 4 °C. Results showed that the efficacy of SAS in inhibiting browning of apple slices increased with increasing concentration. A minimum 3% of SAS was needed to achieve 14 d of shelf life. Firmness was not significantly affected by SAS at 3% or lower concentrations. Antibrowning potential of SAS was similar for all treatment times ranging from 2 to 10 min. However, SAS caused some skin discoloration of apple slices. When cut surface of apple slices were stained with a fluorescein diacetate solution, tissue damage could be observed under a microscope even though visual damage was not evident. Among the antibrowning agents tested, SAS was the most effective in inhibiting browning and microbial growth for the first 14 d. Total plate count of samples treated with 3% SAS was significantly lower than those treated with calcium ascorbate, a commonly used antibrowning agent. Our results suggested that it is possible to use SAS to control browning while inhibiting the growth of microorganisms on the apple slices if the skin damage can be minimized. Practical Application: Fresh‐cut apples have emerged as one of the popular products in restaurants, schools, and food service establishments as more consumers demand fresh, convenient, and nutritious foods. Processing of fresh‐cut apples induces mechanical damage to the fruit and exposes apple tissue to air, resulting in the development of undesirable tissue browning. The fresh‐cut industry currently uses antibrowning agents to prevent discoloration. However, the antibrowning solutions can become contaminated with human pathogens such as Listeria monocytogenes, and washing of apple slices with the contaminated solutions can result in the transfer of pathogens to the product. It would be ideal if an antibrowning compound prevented the proliferation of human pathogens in solutions and minimized the growth of pathogens during storage. The study was conducted to investigate antibrowning and antimicrobial properties of sodium acid sulfate (SAS) in comparison with other common antibrowning agents on Granny Smith apples. Results showed that among the antimicrobial agents we tested, SAS was the most effective in inhibiting browning and microbial growth for 14 d at 4 °C. However, SAS caused some skin discoloration of apple slices. Overall, SAS can potentially be used to inhibit tissue browning while reducing the microbial growth on apple slices. The information is useful for the fresh‐cut produce industry to enhance microbial safety of fresh‐cut apples while minimizing browning, thus increasing the consumption of the health benefiting fresh fruit.     

氧化白藜芦醇对鲜切苹果及果汁褐变的影响

为研究氧化白藜芦醇(oxyresveratrol,OXY)对苹果褐变的抑制作用,采用不同浓度的OXY对鲜切苹果、苹果汁进行处理,探讨在不同储藏阶段切片色度和果汁褐变度变化情况及OXY对苹果汁内多酚氧化酶(polyphenol oxidase,PPO)和过氧化物酶(peroxidase,POD)活性的影响。结果表明:OXY可改善苹果切片的感官品质,显著延缓切片L^*值的降低(P<0.05),抑制a^*、b^*、ΔE值的升高(P<0.05)。同时,OXY还能显著降低苹果汁褐变度(P<0.05),显著抑制苹果汁内PPO和POD活性(P<0.05)。综上,OXY能有效抑制鲜切苹果片及苹果汁褐变,其作用机制可能是通过抑制苹果内PPO和POD活性实现。     

预处理对微波膨化苹果脆片质量的影响

通过研究物料厚度、水分含量、预干燥温度、均湿时间等预处理操作对微波膨化苹果脆片的膨化效果及品质影响，得出较佳的工艺参数。试验表明，在苹果片厚度为5mm、苹果片初始水分含量18％，预干燥温度85℃，均湿时间3d，微波功率为中档火，微波时间30s时，所得苹果脆片膨化效果及品质较好。     

Control of browning and microbial growth on fresh-cut apples by sequential treatment of sanitizers and calcium ascorbate

ABSTRACT:  This study investigated the efficacy of different sanitizers, including acidic electrolyzed water (AEW), peroxyacetic acid (POAA), and chlorine, on the inactivation of Escherichia coli O157:H7 on fresh-cut apples. The effects of the sanitizers and sequential treatments of AEW or POAA followed by calcium ascorbate (CaA) on browning inhibition and organoleptic qualities of fresh-cut apples stored under different package atmospheres at 4 °C were also evaluated. Changes in package atmosphere composition, product color, firmness, total aerobic bacterial counts, yeast and mold counts, and sensory qualities were examined at 0, 4, 8, 11, and 21 d. Among all sanitizer treatments, POAA and AEW achieved the highest reduction on E. coli O157:H7 populations. The sequential treatment of AEW followed by CaA (AEW-CaA) achieved the best overall dual control of browning and bacterial growth on fresh-cut apple wedges. Package atmospheres changed significantly over time and among package materials. Packages prepared with films having an oxygen transmission rate (OTR) of 158 had significantly lower O₂ and higher CO₂ partial pressures than those prepared with 225 OTR films and the Ziploc™ bags. The effect of package atmospheres on the browning of apples is more pronounced on AEW, POAA, and POAA-CaA-treated apple wedges than on AEW-CaA-treated samples.     

不同包装方式对鲜切秦冠苹果贮藏品质的影响

以市售秦冠苹果为试材,结合柠檬酸保鲜剂处理,研究4 ℃贮藏条件下,普通包装、真空包装、高氧包装及充氮包装对鲜切秦冠苹贮藏品质变化规律的影响,确定最佳包装方式。结果表明:在综合鲜切苹果贮藏期各项指标的前提下,真空包装对鲜切苹果保鲜效果最佳,使鲜切苹果外观品质得以保持,延缓鲜切苹果的褐变进程和可溶性固形物含量降低速率,同时抑制了鲜切苹果贮藏期间多酚氧化酶(polyphenol oxidase,PPO)和过氧化物酶(peroxidase,POD)活性,减缓丙二醛(malondiadehyde,MDA)含量的升高。     

基于磁电辅助浸渍的鲜切苹果钙离子强化研究

利用互感方法获得交变感应电场,并结合旋转磁场作用,固定磁感应强度0.13 m T、旋转频率1 Hz下对浸渍溶液中的鲜切苹果进行钙离子强化处理,即以交变电场力和交变磁场力共同作用加速自由离子在苹果组织中的扩散,考察不同激励电压、激励信号种类、脉冲信号占空比和溶液种类对苹果中钙含量的影响,发现激励电压越高则越有利于钙离子在苹果中的扩散。经过脉冲波处理后的样品相对于正弦波、三角波和锯齿波处理的样品其钙离子含量最高。不同电导率的浸渍溶液体系中,其蔗糖-氯化钙溶液处理后的鲜切苹果钙含量最高可达94 mg/100 g,相对于其他2种浸渍体系即蔗糖-乳酸钙和蔗糖-葡萄糖酸钙体系,钙含量则分别提高了119.0%和91.6%,且样品的钙含量增加趋势在50 min后变缓,该研究为钙离子在多孔状植物组织中的渗透提供了一种参考方法。     

Texture of Vacuum Microwave Dehydrated Apple Chips as Affected by Calcium Pretreatment, Vacuum Level, and Apple Variety

ABSTRACT: The effects of calcium pretreatment, vacuum level, and apple variety on the texture of apple chips, processed using a combination of air drying and vacuum microwave dehydration (VMD), were determined. Pretreatment of apple slices by immersion in 1-5% aqueous CaCl₂ significantly increased crispness of chips as determined by instrumental and sensory analysis; however above 1%, chips were perceived as bitter. Higher vacuum applied during VMD significantly lowered density and increased crispness of chips. This effect was mediated by the vaporization of water in the interior of the chip, which caused expansion of the tissue. Chips made from Fuji apples had higher calcium contents, and were crisper than Red and Golden Delicious apple chips. Microstructure of the chips evaluated by scanning electron microscopy indicated that chips with thicker cell walls and large internal voids were crisper.     

柠檬酸处理对鲜切苹果的保鲜效果

为研究柠檬酸处理对鲜切苹果品质的影响,将鲜切‘寒富’苹果分别放入0.5%、1.0%、1.5%柠檬酸溶液中浸泡2 min后沥干,用0.11 mm厚度的聚乙烯保鲜膜包装后置于4 ℃冷库中贮藏,每2 d检测与成熟衰老相关生理生化指标。结果表明,适当质量分数的柠檬酸处理可保持苹果切块的感官品质,延缓营养物质的下降,抑制微生物的繁殖,对鲜切苹果有较好的护色效果;1.5%柠檬酸溶液浸泡处理能在8 d贮藏期内4 ℃冷藏条件下保持着鲜切苹果的良好品质,能有效延迟果肉褐化进程,降低褐变程度,抑制硬度和可溶性固形物、可滴定酸及抗坏血酸含量的下降,并能延缓相对电导率和丙二醛含量的上升,降低多酚氧化酶、过氧化物酶的活性。     

Quality Changes in Fresh-cut Pear Slices as Affected by Cultivar, Ripeness Stage, Fruit Size, and Storage Regime

Fresh-cut fruit slices prepared from partially ripened Bartlett pears had longer shelf life than those from Bosc, Anjou, and Red Anjou pears. Pear fruit ripeness, based on flesh firmness of 44 to 58 N, is optimal for fresh-cut pear slice processing. Pear slices derived from smaller size fruit (122 to 135 g) have greater cut surface discoloration and deteriorate more rapidly than slices derived from larger fruit (152 g). Recently harvested Bartlett pear fruit and whole pears held at –1 °C in a controlled atmosphere of 2%O₂+ 98%N₂ had a longer post-cutting shelf life than those held in air at –1 °C for the same duration. Cut surface browning, flesh softening, and surface dehydration of the slice cut surface were all contributors to loss of product quality.     

Effect of Sequential Treatment of Warm Water Dip and Low-dose Gamma Irradiation on the Quality of Fresh-cut Green Onions

ABSTRACT: The effect of warm water dip in combination with irradiation on quality of fresh-cut green onions was studied. Fresh-cut green onions were treated with and without warm water (50°C for 20 s) and packaged prior to irradiation at 0, 0.5, 1.0, and 1.5 kGy, then stored at 4°C for 14 d. Color, texture, decay percentage, electrolyte leakage, sensory qualities, and total aerobic count (TAC) were measured at 1,4,8, and 14 d of storage. The warm water treatment reduced the TAC by 0.9 log initially but the beneficial effect disappeared during storage. With the test conditions used in this study, the warm water treatment did not provide added benefits for quality improvements. Irradiation at all tested doses reduced TAC and the development of decay and off-odor, improved visual quality, and preserved green color.     

真空油炸苹果脆片防潮降油研究

本文报道了真空油炸苹果脆片防潮、降油的新方法。在35％的麦芽糊精溶液(以下略为B)、B和0.3％的胍尔豆胶。B和0.3％CMC-Na分别浸渍之后,油炸的苹果脆片在相对空气湿度100％条件下,能保持其脆性5小时以上,而其它糖浸渍的苹果脆片较快变软。B和0.3％胍尔豆胶、B和0.3％CMC-Na浸渍、油炸的苹果脆片,含油率降为10％左右。     

三种不同预处理的冻干苹果片品质比较

为了解决冻干苹果片加工过程中的护色问题,设计了对照组(CK)、热烫组(BT)、护色液浸泡组(CP)、热烫-护色液浸泡复合护色组(BCP)四组,再采用真空冷冻干燥技术将苹果片制成即食脆片,对每组产品的含水率、维生素C含量、滴定酸度、复水比、质构、色差、感官评价、微观结构等品质进行比较分析.结果表明,四组冻干苹果片的含水率...     

Quality Change of Apple Slices Coated with Aloe vera Gel during Storage

Fresh‐cut apples are easily susceptible to browning and microbial spoilage. In this study, an edible coating prepared from Aloe vera gel containing antibrowning solution was applied to preserve the quality of fresh‐cut apples during storage. Fresh‐cut apples were treated with both an Aloe vera gel and an Aloe vera gel containing 0.5% cysteine and then stored at 4 °C for 16 d. The color, firmness, weight loss, soluble solid content, titratable acidity, microbial analysis, and sensory evaluation were analyzed during storage. Fresh‐cut apples coated with the Aloe vera gel showed delayed browning and reduced weight loss and softening compared to the control. The Aloe vera gel coating was also effective in reducing the populations of the total aerobic bacteria and yeast and molds. In particular, Aloe vera gel containing 0.5% cysteine was most effective in delaying browning and the reduction of microbial populations among the treatments. These results suggest that an Aloe vera gel coating can be used for maintaining the quality of fresh‐cut apples.