鲜切马铃薯褐变抑制效果研究

本文采用含硫化合物L-半胱氨酸、酸化剂苯甲酸、酶底物竞争性抑制剂肉桂酸、防腐剂山梨酸；螯合剂β-环糊精等褐变抑制剂对鲜切马铃薯褐变的抑制效果进行了研究。通过褐变度与多酚氧化酶活性相关分析和比较确定了不同抗褐变剂实际效果。结果表明，L-半胱氨酸、肉桂酸、苯甲酸对鲜切马铃薯具有良好的抗褐变效果。     

鲜切梨褐变抑制的研究

研究了不同褐变抑制剂对鲜切梨褐变度、PPO活性、感官品质的影响。实验结果表明,单一使用1.0%柠檬酸、0.01%水杨酸、0.3%L半-胱氨酸处理均能较好的抑制鲜切梨褐变。但是采用0.3%L-半胱氨酸+0.01%水杨酸+1.2%柠檬酸,浸泡9m in的复合处理效果最佳,可使鲜切梨的褐变度在12d内保持较优水平。      

鲜切芋艿褐变特性研究

以两种芋艿品种（江苏昆山产和山东威海产）为材料，研究了4℃贮藏下芋艿色差L＊a＊b＊值、还原糖和抗坏血酸含量、褐变潜力、多酚氧化酶、过氧化物酶、苯丙氨酸解氨酶等酶活力的变化。结果表明：褐变是影响鲜切芋艿品质的主要因素，可通过L＊a＊b＊来反映；多酚氧化酶是参与芋艿褐变的主要酶；高含量的还原糖和抗坏血酸有利于抑制褐变。通过对两个品种芋艿褐变特性的比较，发现威海产芋艿是较适合于鲜切牛产的一个品种。     

鲜切苹果褐变抑制的研究

以柠檬酸、氯化钠、乙二胺四乙酸二钠、D-异抗坏血酸钠对鲜切苹果进行独立及复合护色处理。结果表明,4种试剂复合的效果优于单独处理,采用L16(45)正交试验,利用各种护色剂的协同作用,得到一种替代亚硫酸盐的新型复合护色液:1.00%柠檬酸+0.80%氯化钠+0.16%乙二胺四乙酸二钠+0.50%D-异抗坏血酸钠。     

鲜切马铃薯褐变控制方法的研究

为了控制鲜切马铃薯在加工过程中的褐变,本研究对鲜切马铃薯褐变控制方法进行了筛选研究,根据单因素实验结果,选取了热烫、亚硫酸盐浸渍和抗坏血酸浸渍等处理方法,经三因素三水平正交试验确定出最佳褐变控制方法为:鲜切马铃薯切片进行60 ℃热烫1 min,2.0%的亚硫酸盐浸渍2 min,0.25%的抗坏血酸溶液浸渍2 min,该处理条件下多酚氧化酶的活力为2 u/mL.     

鲜切竹笋褐变控制的研究

以鲜切竹笋为原料,蒸馏水为对照,采用3种浸泡液处理,即0.5%柠檬酸处理,45℃热水处理,0.5%柠檬酸和45℃热水联合处理,探讨鲜切竹笋褐变的机理及控制方法.试验结果表明,鲜切竹笋褐变主要是由于过氧化物酶(POD)引起的酶促褐变;0.5%柠檬酸和45℃热水联合处理可有效降低POD和多酚氧化酶(PPO)的活性,抑制鲜切竹笋POD同工酶的合成,从而有效抑制其引起的酶促褐变.     

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。     

半胱氨酸控制鲜切苹果褐变的生理机制

为研究半胱氨酸对鲜切苹果褐变控制的生理机制,以鲜切苹果为研究对象,采用0.5 g/L的半胱氨酸溶液处 理1 min,分析贮藏过程中鲜切苹果褐变指数（browning index,BI）、多酚氧化酶（polyphenol oxidase,PPO）和 抗氧化酶活力、抗氧化物质和丙二醛（malondialdehyde,MDA）质量摩尔浓度及抗氧化能力的变化。结果表明, 与蒸馏水处理相比,半胱氨酸处理能够显著抑制鲜切苹果的褐变,在贮藏初期半胱氨酸处理降低了鲜切苹果的PPO 活力,同时在贮藏过程中不同程度提高了鲜切苹果的抗氧化酶活力以及抗氧化能力,减缓了抗氧化物质在贮藏过程 中的损失,并且抑制了MDA的积累。相关性分析显示,鲜切苹果的BI值与抗坏血酸含量、过氧化氢酶活力以及抗 氧化能力呈极显著负相关（P＜0.01）,与MDA质量摩尔浓度呈极显著正相关（P＜0.01）。因此,半胱氨酸可能是 一方面通过抑制鲜切苹果的PPO活力,另一方面通过提高其抗氧化能力,延缓贮藏过程中的组织褐变。     

鲜切荸荠褐变抑制剂组合的筛选

新鲜荸荠经过清洗、挑选、去皮后采用不同抑制剂组合按L9（34）处理,在4℃下贮藏。贮藏期间定期检测鲜切荸荠的褐变度（BD值）、总酚含量（TP）、多酚氧化酶（PPO）和苯丙氨酸转氨酶（PAL）的活性。正交实验结果表明,防褐变的最佳抑制剂组合为0.2%异抗坏血酸（D-AA）+0.05%N-甲酰-L-半胱氨酸（AC）+1.0%的柠檬酸（CA）。与对照（清水）相比,该组合可以较好地抑制鲜切荸荠的褐变,但略差于0.1%亚硫酸氢钠的处理。鲜切荸荠BD值与TP含量、PPO和PAL的活性有显著的相关性。      

鲜切苹果物理防褐变技术研究进展

鲜切苹果在加工过程中受到组织损伤与破坏,导致发生褐变、营养物质流失等问题,使其食用价值与商业价值降低,造成损失,因此需要保鲜技术手段加以控制。物理保鲜方式具有无毒无害、操作方便简单等特点,在国内外受到广泛的推广。该文基于鲜切苹果劣变机理,阐述物理防褐变保鲜技术在鲜切苹果中的研究进展,从温度调控、气调贮藏技术、光电方法等方面论述不同的物理方法对鲜切苹果防褐变效果,旨在提供不同的物理保鲜方法对鲜切苹果的应用依据。     

Using polysaccharide-based edible coatings to maintain quality of fresh-cut Fuji apples

The effect of alginate and gellan-based edible coatings on the shelf-life of fresh-cut Fuji apples packed in trays with a plastic film of a known permeability to oxygen (110 cm³ O₂ m⁻² bar⁻¹ day⁻¹) was investigated by measuring changes in headspace atmosphere, color, firmness and microbial growth during 23 days of storage at 4 °C. Concentration of O₂ and CO₂ in the package was measured and no significant differences between coated and uncoated fresh-cut apples were observed. Ethylene concentration in coated apples seemed to be delayed since it remained below 50 μl l⁻¹ throughout the whole refrigerated storage period, while production of this gas was detected in uncoated apples from the very initial days of storage. Coated apple wedges exhibited ethanol and acetaldehyde formation from the second week of storage indicating fermentative metabolism. Polymers were crosslinked with a calcium chloride solution, to which the antibrowning agent N-acetylcysteine was added, being incorporated into the coatings formulation and helping to maintain firmness and color of apple wedges during the entire storage time. The application of the edible coatings also retarded the microbiological deterioration of fresh-cut apples. Alginate and gellan edible coatings effectively prolonged the shelf-life of Fuji apple wedges by 2 weeks of storage compared with the control apple slices which showed a considerable cut surface browning and tissue softening from the very early days of storage, limiting their shelf-life to less than 4 days.     

可食性复合涂膜保鲜剂对延长鲜切苹果货架期的研究

本文主要研究了可食性涂膜剂与抗褐变剂复配后对3℃条件下贮存2周的鲜切苹果的保鲜效果。研究表明：25℃条件下，苹果切块经卡拉胶（0．5％）涂膜剂和乳清浓缩蛋白WPC（5％）涂膜剂处理后，其呼吸强度可分别降低5％和20％，可食性涂膜剂与抗褐变剂复配后，对3℃贮藏2周的苹果切块可明显延长其货架期，在涂膜剂中添加不同的抗褐变剂对苹果切块有良好的护色效果，添加1％CaCl，可增加产品的硬度，同时这些复合保鲜剂可提高苹果切块的感官指标和抑制微生物繁殖，而5％乳清浓缩蛋白＋1％CaCl2＋1％抗坏血酸复合液浸泡苹果切块，3℃条件贮藏2周后保鲜效果最佳。     

Influence of harvest maturity on cut-edge browning of ‘Granny Smith’ fresh apple slices treated with anti-browning solution after cutting

Over several years, many fresh-cut apple processors have complained about browning of slices made from ‘Granny Smith’ apples during the harvest season, before fruit have been stored for any length of time. ‘Granny Smith’ apples are a late harvest apples and quite often, at higher latitudes, they are harvested to avoid frost injury and may not always be physiologically mature. It was postulated that immature fruit would have greater susceptibility to browning, despite the application of anti-browning solution after cutting. Fruits were harvested from selected trees beginning five weeks before anticipated commercial harvest and continued weekly until two weeks after commercial harvest. The maturity indicators internal ethylene and starch clearing indices were measured. Ten fruits were sliced, dipped in 7 g L⁻¹ NatureSeal^® and then packaged in zip-loc bags and held at 5 °C. Slices made from apples that were harvested two weeks early or earlier than the optimal maturity, as determined by the maturity measures, had significant levels of cut-edge browning despite the post-cutting application of anti-browning dip. These results clearly indicate that ‘Granny Smith’ apples harvested two weeks or earlier before induction of climacteric ethylene production (when starch index is less than 2.5) should be avoided for use in fresh slicing.     

Browning characteristics of fresh-cut ‘Tsugaru’ apples as affected by pre-slicing storage atmospheres

The change in browning characteristics of the slices processed from ‘Tsugaru’ apples stored at 0 °C for 5 months under controlled atmosphere (CA, 1 kPa O₂ + 1 kPa CO₂, 3 kPa O₂ + 3 kPa CO₂) or air has been investigated for 5 days at 20 °C. Respiration and ethylene production of the slices from apples stored in CA were retarded. Electrolyte leakage and browning index were lower in the slices from apples stored under CA than air. Vitamin C and phenolic contents in the slices from apples stored under air were maintained at higher level compared to the slices from apples stored under CA. Polyphenol oxidase activity in the slices was not affected by pre-slicing storage atmospheres. Therefore, the atmospheres of pre-slicing storage affected browning development in fresh-cut products of ‘Tsugaru’ apples and browning was found to be correlated with the levels of electrolyte leakage and phenolic compounds.     

Dual effectiveness of sodium chlorite for enzymatic browning inhibition and microbial inactivation on fresh-cut apples

The dual effectiveness of sodium chlorite for browning inhibition and microbial inactivation on fresh-cut apples was investigated and compared to other anti-browning and antimicrobial agents. Results indicate that sodium chlorite significantly (P < 0.001) inhibited the browning reaction of fresh-cut Red Delicious apples stored at 5 °C for 14 days. This treatment also significantly reduced polyphenol oxidase activities. Treatments with acidified sodium chlorite, calcium chloride, or calcium ascorbate exhibited strong inhibition on apple browning during the early storage, these treatment effects diminished after 7 days in storage. Combining calcium chloride with sodium chlorite further significantly (P < 0.001) improved the firmness of apple slices, and browning inhibition during storage. Additionally, treatments with acidified sodium chlorite, sodium chlorite, or the combination of sodium chlorite and calcium chloride significantly (P < 0.001) reduced Escherichia coli populations on fresh-cut apples by 3.0, 3.6, and 3.9 log cfu g⁻¹ over the water control. The dual effectiveness of sodium chlorite to inhibit enzymatic browning and inactivate E. coli may allow this compound to achieve a prominent role in improving the quality and safety of products in the fresh-cut apple and other food industries.     

Sensory effects of hexanal vapor on fresh-cut slices of golden delicious apples

Hexanal is a natural antimicrobial molecule that characterizes apples aroma. In this paper, the sensory effects of hexanal, as a component of packaging atmosphere, on fresh sliced Golden Delicious apples after storage at 4 °C for 8 d were evaluated. In particular, a colorimetric analysis of slices treated with different concentrations of hexanal vapor (coming from 3.040 to 0.076 mmol of liquid aldehyde per liter of air) fixed at 0.076 mmol/L the amount of hexanal in evaluating sensory effects in the subsequent analysis. Color and texture evaluation of slices by Two-out-of-Five method did not highlight any significant difference between treatment and control. The results from olfactory evaluation showed instead that treated samples had an intense odor compared with those untreated (P < 0.001). A significant difference between treatment and control was also highlighted during the flavor evaluation (P < 0.01); however, from the panelists' observations it emerged that such an effect would work negatively. The positive effect of the tested dose of hexanal on the odor of Golden Delicious slices and its flavor acceptability were verified by using regular apple consumers. A significant preference (P < 0.001) for the odor of treated apple slices came out, so the small dose of hexanal intensifies the odor of apples pleasantly. The different flavor of treated samples was not identified by the consumers, who altogether expressed positive judgments about it. This suggests the nicety of this difference that in the absence of an untreated reference sample is very difficult to detect.     

Sensory quality and internal atmosphere of fresh-cut Golden Delicious apples

The sensory shelf‐life of Golden Delicious fresh‐cut apples, dipped in 10 g L^?1 ascorbic acid and 5 g L^?1 calcium chloride and packaged under different modified atmosphere conditions, was assessed throughout refrigerated storage. An initial atmosphere of 0 kPa O₂ and plastic packages of an O₂ permeability of 15 cm³ m^?2 bar^?1 day^?1 were very effective in preserving the initial colour and firmness of apple cubes during at least 3 weeks of storage. These conditions resulted in increased respiration coefficients, which curbed the product consumer acceptance beyond the second week of storage. However, reduced ethylene and CO₂ production limited the appearance of fermentative metabolites during this period.     

Effects of an innovative dipping treatment on the cold storage of minimally processed Annurca apples

The effect of trehalose as an edible coating on minimally processed Annurca apple slices was studied during cold storage. The edible coating was prepared by dipping the fruit in a solution containing trehalose at 0.8%, sucrose at 1.0% and sodium chloride at 0.1%. During storage at 6 °C the following parameters were monitored: weight loss, colour (hue angle (h°) and whitening index (WI)), firmness, malic and ascorbic acids, polyphenol content, microstructure by scanning electron microscopy (SEM) and microbial count. The results showed that such a coating reduced the browning phenomena; in fact the WI and h° values were significantly lower in coated samples than untreated ones. Moreover, decreases in weight loss and in the reduction of organic acids were observed in coated samples. Electron microscopy slides of the cut tissue showed how the coating worked.     

Efficacy of thyme oil-alginate-based coating in reducing foodborne pathogens on fresh-cut apples

In this study, the inhibition of an alginate-based edible coating (EC) containing thyme oil (0.05%, 0.35% and 0.65%) was evaluated against Listeria monocytogenes, Salmonella Typhimurium, Staphylococcus aureus and Escherichia coli O157:H7 inoculated onto fresh-cut apples. To investigate the antibacterial mechanism of thyme oil, the constituent compounds of that were analysed by gas chromatography-mass spectrometry (GC-MS), and the cellular damage of pathogens was observed by scanning electron microscopy (SEM). Results showed that alginate-based EC containing thyme oil effectively inhibited the growth of pathogens on fresh-cut apples. GC-MS analysis revealed thymol (47.23%) as the major compounds in thyme oil. SEM showed that the cell membrane of foodborne pathogens was damaged by thyme oil, causing their inactivation. Treatment with alginate-based EC containing 0.05% thyme oil preserved the sensory characteristics of fresh-cut apples. Therefore, using alginate-based EC with thyme oil may represent a potential approach to preserve and enhance the safety of fresh-cut apples.     

水杨酸处理对鲜切富士苹果抗氧化性的影响

主要探讨了外源水杨酸（SA）溶液处理对贮藏中的鲜切苹果在一段时期内的生理生化的影响。选用0.25mmol.L-1的水杨酸溶液处理鲜切苹果,清水浸泡为对照,5℃贮藏,并测定此条件下鲜切苹果生理生化的变化情况。实验结果表明,0.25mmol.L-1的水杨酸溶液处理可以有效地抑制鲜切苹果中谷胱甘肽还原酶（GR）和抗坏血酸过氧化物酶（APX）的活性,抑制鲜切苹果膜脂过氧化的程度和超氧阴离子O2-.的产生,减少过氧化氢（H2O2）的含量,并防止了总酚和VC含量的下降。由此可见,0.25mmol.L-1的水杨酸溶液处理可以提高鲜切苹果的抗氧化性以及保护其营养物质,改善鲜切苹果的内在品质。