The effects of ethanol treatment on the metabolism,shelf life and quality of stored tomatoes at different maturities and temperatures

Two maturity stages of commercially grown tomatoes (breaker and mature green) were exposed to ethanol vapour (2 ml ethanol kg⁻¹ fruit) for 6 h at 20 °C prior to storage at 5 °C and 20 °C. During storage the colour, firmness and composition changes were examined every 3 and 7 days. The results showed that ethanol vapour treatment could significantly slow down the colour changes and softening of both mature green and breaker tomatoes with greater effects when stored at 5 °C. There was no difference between the two maturity stages in retardation of softening during storage; in contrast the maturity stage had a highly significant effect in the colour development of stored tomatoes. When the fruit stored at 5 °C was then held at 20 °C for 7 days the ripening process was accelerated but the fruit did not reach the same level of colour development as the fruit stored at 20 °C continuously. The results suggest that ethanol vapour pretreatment could be used as a cheap and easy method to extend the storage life of tomatoes. © 1999 Society of Chemical Industry     

The effects of X-ray radiation on Escherichia coli O157:H7, Listeria monocytogenes, Salmonella enterica and Shigella flexneri inoculated on whole Roma tomatoes

In the last two decades several foodborne disease outbreaks associated with produce were reported. Tomatoes, in particular, have been associated with several multi-state Salmonella outbreaks. Inactivation of inoculated Escherichia coli O157:H7, Listeria monocytogenes, Salmonella enterica and Shigella flexneri on whole Roma tomato surfaces by X-ray at 0.1, 0.5, 0.75, 1.0, and 1.5 kGy was studied. The main purpose of this study was to achieve a 5 log reduction in consistent with the recommendations of the National Advisory Committee on Microbiological Criteria for Foods. Moreover, the effect of X-ray on inherent microflora (mesophilic counts, psychrotrophic counts and yeast and mold counts) of untreated and treated Roma tomatoes, during storage at ambient temperature (22 °C) for 20 days was also determined. Mixtures of three or two strains of each tested organism was spot inoculated (100 μl) onto the surface of Roma tomatoes (approximately 7–9 log per tomato), separately, and air-dried, followed by treatment with X-ray doses at 22 °C and 55–60% relative humidity. Surviving bacterial populations on tomato surfaces were evaluated using a nonselective medium (tryptic soy agar) with a selective medium overlay for each bacteria; E. coli O157:H7 (CT-SMAC agar), L. monocytogenes (MOA), and S. enterica and S. flexneri (XLD). Treatment with X-ray significantly reduced the population of the tested pathogens on whole Roma tomato surfaces, compared with the control. Approximately 4.2, 2.3, 3.7 and 3.6 log CFU reduction of E. coli O157:H7, L. monocytogenes, S. enterica and S. flexneri per tomato were achieved by treatment with 0.75 kGy X-ray, respectively. More than a 5 log CFU reduction per tomato was achieved at 1.0 or 1.5 kGy X-ray for all tested pathogens. Furthermore, treatment with X-ray significantly reduced the inherent microflora on Roma tomatoes. Inherent levels were significantly (p < 0.05) lower than the control sample throughout storage for 20 days.     

50%异菌脲·腐霉利悬浮剂在设施和露地番茄上的残留与安全性评价

目的 开展50%异菌脲·腐霉利悬浮剂在设施和露地番茄上的残留试验, 评价其在番茄上使用的安全性。方法 2021年在北京、辽宁、甘肃、山西、山东、浙江、河南、江苏、贵州、河北、湖南和重庆的番茄主产区开展了田间试验, 番茄样品用乙腈涡旋提取, N-丙基乙二胺、石墨化碳黑和十八烷基碳混合分散吸附剂净化, 超高效液相色谱分离, 三重四极杆串联质谱检测, 基质标准曲线-外标法定量。结果 设施番茄中异菌脲和腐霉利的降解半衰期分别为11.5和12.3 d, 露地番茄中异菌脲和腐霉利的降解半衰期分别为6.9和7.8 d。50%异菌脲·腐霉利悬浮剂在番茄上按最高剂量525 g a.i/hm2施药3次后, 安全间隔期7 d时, 设施番茄中异菌脲的最终残留量为0.10~0.73 mg/kg, 腐霉利的最终残留量为0.14~1.67 mg/kg, 露地番茄中异菌脲的最终残留量为<0.01~0.25 mg/kg, 腐霉利的最终残留量为<0.01~0.58 mg/kg。结论 依据GB 2763—2021《食品安全国家标准 食品中农药最大残留限量》中规定的异菌脲和腐霉利的最大残留限量标准, 收获的番茄食用是安全的。本研究结果为50%异菌脲·腐霉利悬浮剂在设施和露地番茄上的安全使用、农药残留量控制和农产品安全提供理论和技术支持。     

基于催化式红外的西红柿干法去皮技术

目的：探寻一种高效且绿色环保的西红柿去皮方法。方法：利用催化式红外设备进行西红柿干法去皮,考察工艺参数对西红柿去皮性能和果肉品质的影响,并与传统的热水和碱液去皮方式进行对比。结果：双板距离、红外加热温度和红外加热时间均对西红柿去皮率和果肉品质有显著影响（P<0.05）,西红柿催化式红外干法去皮的最优工艺参数为催化红外温度450 ℃,双板距离25 cm,红外处理时间5 min,此时西红柿去皮率高达98%,且果肉硬度（7.60 g/mm²）和番茄红素含量（30.39 mg/kg）最优,颜色鲜红。与传统热水和碱液去皮方式相比,红外去皮属于干法去皮,是一种环境友好型的去皮方法;红外去皮处理后西红柿果肉具有最高的硬度、番茄红素含量,颜色更红润,果肉完整性良好;红外去皮处理对果皮和果肉微观结构的影响最小,对果皮果肉连接层的微观结构有明显影响,促进了果皮与果肉的分离,表明红外去皮机制与其他几种去皮方式不同。结论：催化式红外去皮方式更适合西红柿的去皮加工,可以实现高效去皮、绿色环保且能保障产品品质。     

Effects of Pseudomonas chlororaphis and gaseous chlorine dioxide on the survival of Salmonella enterica on tomatoes

Control of Salmonella enterica on tomatoes is important for food safety. The aim of this research was to evaluate the survival of Salmonella enterica serovars Montevideo (SM) and Typhimurium (ST) on tomatoes exposed to gaseous chlorine dioxide and Pseudomonas chlororaphis (Pc). Pc was applied to stem scars of tomatoes prior to inoculations with SM and ST. Tomatoes were treated with gaseous ClO₂ at 0.4 mg L^?1 for 2 and 4 h (90% R.H. 13 °C), respectively. At 4 h of ClO₂ treatment, SM and ST populations were reduced to 0.82 and <0.30 log CFU g^?1, respectively. Tomatoes treated with SM and ST had 5.42 and 5.37 log CFU g^?1 of Salmonella. Tomatoes treated with Pc + Salmonella count was 2.59 (treated) and 5.83 log CFU g^?1 (control). Salmonella survival was similar at 2 and 4 h of ClO₂ treatment. Application of ClO₂ and Pc may reduce contamination of tomatoes by Salmonella serovars.     

Efficacy of Neutral pH Electrolyzed Water in Reducing Escherichia coli O157:H7 and Salmonella Typhimurium DT 104 on Fresh Produce Items using an Automated Washer at Simulated Food Service Conditions

The objective of this study was to determine the efficacy of neutral pH electrolyzed (NEO) water (155 mg/L free chlorine, pH 7.5) in reducing Escherichia coli O157:H7 and Salmonella Typhimurium DT 104 on romaine lettuce, iceberg lettuce, and tomatoes washed in an automated produce washer for different times and washing speeds. Tomatoes and lettuce leaves were spot inoculated with 100 μL of a 5 strain cocktail mixture of either pathogen and washed with 10 or 8 L of NEO water, respectively. Washing lettuce for 30 min at 65 rpm led to the greatest reductions, with 4.2 and 5.9 log CFU/g reductions achieved for E. coli O157:H7 and S. Typhimurium respectively on romaine, whereas iceberg lettuce reductions were 3.2 and 4.6 log CFU/g for E. coli O157:H7 and S. Typhimurium respectively. Washing tomatoes for 10 min at 65 rpm achieved reductions greater than 8 and 6 log CFU/tomato on S. Typhimurium and E. coli O157:H7 respectively. All pathogens were completely inactivated in NEO water wash solutions. No detrimental effects on the visual quality of the produce studied were observed under all treatment conditions. Results show the adoption of this washing procedure in food service operations could be useful in ensuring produce safety.     

海藻酸钠和溶菌酶复合涂膜对樱桃番茄贮藏的保鲜效果

以海藻酸钠和溶菌酶为保鲜剂对樱桃番茄进行复合涂膜保鲜,研究不同浓度的海藻酸钠溶液对樱桃番茄贮藏保鲜效果的影响,分析了各处理组对樱桃番茄的感官品质、腐烂指数、失重率、硬度、呼吸强度、Vc含量、可溶性固形物含量以及SOD酶活性等生理生化指标的变化。结果表明:经1%海藻酸钠+0.1%溶菌酶处理后的樱桃番茄,在4℃条件下贮藏25 d后,其感官品质、果实的失重率明显优于其他处理,Vc含量为26.4mg/100g、可溶性固形物含量为10.9%、呼吸强度显著低于其他处理组,综合保鲜效果最佳。     

Ultrasonication as pretreatment for drying of tomato slices in a hot air–microwave hybrid oven

This study aims to investigate the effect of ultrasonic pretreatment on drying time and quality properties of tomato slices dried by microwave combined with hot air at 60°C. The influence of ultrasound pretreatment (0, 20, and 40?min) and microwave power (120, 150, and 180?W) on drying time, color, total phenolic content, lycopene, vitamin C, and rehydration capacity of dried slices of tomato was studied. Results showed that as the microwave power level increased, drying time decreased significantly (about 46.4%). Ultrasound pretreatment decreased the drying time by 7.38% only at 120?W microwave power and 40?min of pretreatment compared to those without ultrasound pretreatment at the same microwave power. Depending on drying conditions, vitamin C and lycopene contents reduced from 433.94 to 81.89?mg AA/100?g dry solids and 3920.57 to 415.40?mg/100?g dry solids, respectively. The change in total phenolic content was not severe as much as vitamin C contents. Rehydration capacity of pretreated samples was larger than nontreated samples. The color values of dried tomato slices were in the acceptable range. Both microwave power and ultrasound pretreatment affected the quality of the final product significantly.     

Selection of reference genes for quantitative real‐time PCR in postharvest tomatoes (Lycopersicon esculentum) treated by continuous low‐voltage direct current electricity to increase secondary metabolites

Quantitative real‐time PCR (RT‐qPCR) is often used for gene expression analysis to reveal molecular mechanism of how stresses can enhance the secondary metabolites production. For RT‐qPCR to be valid, robust reference genes are required. This study validated nine candidate genes as reference genes using BestKeeper, NormFinder and geNorm methods in RT‐qPCR analysis of postharvest tomatoes subjected to electricity‐induced stress. The most stable genes as indicated by each method were EF‐1α by BestKeeper; CAC by NormFinder; and PP2Acs/TIP41 by geNorm. Due to the inconsistency in the ranking of the candidate genes by the three methods, the pairwise variation from geNorm analysis was used to calculate the minimum numbers of reference genes for an accurate normalisation and revealed that a combination of PP2Acs and TIP41 was an optimum. This reference gene combination was further validated for their stability in RT‐qPCR analysis of four carotenoid‐related genes, and more reliable expression levels were obtained.     

四种物流贮藏温度对圣女果品质的影响

以圣女果为材料,研究了常温（20℃）,变温（先在5±1℃保存4d,再转移到20℃下保存）,低温（5±1℃）和冰温（-0.5±0.5℃）四种物流温度对圣女果的外观品质、营养品质的影响规律。结果表明,低温和冰温贮藏可显著地减少可溶性固形物、维生素C的损失,有效地保持其色泽和质地,一定程度上抑制其腐烂率、失重率的增长和酸度的变大。与此同时,冰温处理的圣女果在解冻后15min便出现冷害现象,失去商品价值。常温和变温贮藏时,圣女果营养成分大量损失,其硬度持续下降。故低温贮藏的保鲜效果最好。