Gómez-López Vicente M, Ragaert Peter, Jeyachchandran Visvalingam, Debevere Johan, Devlieghere Frank
Laboratory of Food Microbiology and Food Preservation, Ghent University, Coupure Links, 653 - 9000 Gent, Belgium.
Int J Food Microbiol. 2008 Jan 15;121(1):74-83. doi: 10.1016/j.ijfoodmicro.2007.11.036. Epub 2007 Nov 17.
Gaseous ClO2 was evaluated for effectiveness in prolonging the shelf-life of minimally processed (MP) lettuce and MP cabbage, previously immersed in a cysteine solution in order to inhibit browning occurring during ClO2 treatment. Each vegetable was shredded, washed, and separated in two portions, one to be treated with ClO2 gas and the other to remain untreated as reference sample. The batch to be treated with ClO2 gas was immersed for 1 min in a 0.5% solution of HCl.L-cysteine monohydrate. Then both batches were spun dried. MP vegetables were decontaminated in a cabinet at 90-91% relative humidity and 22-25 degrees C up to 10 min, including 30 s of ClO2 injection into the cabinet. The ClO2 concentration rose to 1.74 mg/L (MP lettuce) and 1.29 mg/L (MP cabbage). Then samples were stored under modified atmosphere at 7 degrees C for shelf-life studies. Changes in O2 and CO2 headspace concentrations, microbiological quality (aerobic plate count (APC), psychrotrophs, lactic acid bacteria, and yeasts), sensory quality, and pH were followed during storage. The respiration rate of the minimally processed vegetables was significantly increased by the ClO2 gas treatment only in the case of MP cabbage (P<0.05). The gas treatment reduced initially APC and psychrotroph count of MP lettuce and APC, psychrotroph counts, yeast counts and pH of MP cabbage (P<0.05). ClO2 treatment did not cause initially any significant (P<0.05) sensorial alteration, except for a weak off-odour in MP lettuce. Interestingly, no browning was observed after treating, which can be accounted to the use of L-cysteine. Although an initial microbiological reduction was observed due to ClO2 gas treatment, APC and psychrotroph counts reached in the samples treated with ClO2 higher levels than in those non-treated with ClO2 before the third day of the shelf-life study. Untreated and treated samples of MP lettuce were sensorial unacceptable due to bad overall visual quality after 4 days, while treated and untreated MP cabbage remained sensorial acceptable during the 9 days of the study. L-cysteine reduced (P<0.05) the decontamination efficacy of ClO2 when applied to MP cabbage but not in the case of MP lettuce. Gaseous ClO2 failed to prolong the shelf-life of MP lettuce and MP cabbage, the reason for the enhanced growth of microorganisms in decontaminated samples should be investigated. Nonetheless, our results prove that it is possible to inhibit browning caused by ClO2.
评估了气态二氧化氯（ClO₂）在延长轻度加工（MP）生菜和MP卷心菜保质期方面的有效性，这些蔬菜先前浸泡在半胱氨酸溶液中，以抑制ClO₂处理过程中发生的褐变。将每种蔬菜切碎、洗涤并分成两部分，一部分用ClO₂气体处理，另一部分作为未处理的参考样品。用ClO₂气体处理的批次在0.5%的盐酸 - L - 半胱氨酸一水合物溶液中浸泡1分钟。然后将两批蔬菜离心干燥。MP蔬菜在相对湿度为90 - 91%、温度为22 - 25摄氏度的柜子中进行去污处理，最长10分钟，包括向柜子中注入30秒的ClO₂。ClO₂浓度升至1.74毫克/升（MP生菜）和1.29毫克/升（MP卷心菜）。然后将样品在7摄氏度的改良气氛下储存以进行保质期研究。在储存期间跟踪氧气和二氧化碳顶空浓度、微生物质量（需氧平板计数（APC）、嗜冷菌、乳酸菌和酵母菌）、感官质量和pH值的变化。仅在MP卷心菜的情况下，ClO₂气体处理显著提高了轻度加工蔬菜的呼吸速率（P<0.05）。气体处理最初降低了MP生菜的APC和嗜冷菌数量以及MP卷心菜的APC、嗜冷菌数量、酵母菌数量和pH值（P<0.05）。ClO₂处理最初没有引起任何显著的（P<0.05）感官变化，除了MP生菜有轻微的异味。有趣的是，处理后未观察到褐变，这可以归因于使用了L - 半胱氨酸。尽管由于ClO₂气体处理观察到微生物数量最初有所减少，但在保质期研究的第三天之前，用ClO₂处理的样品中的APC和嗜冷菌数量比未用ClO₂处理的样品中更高。4天后，由于整体视觉质量差，MP生菜的未处理和处理样品在感官上都不可接受，而在研究的9天内，处理和未处理的MP卷心菜在感官上仍然可以接受。当应用于MP卷心菜时，L - 半胱氨酸降低了（P<0.05）ClO₂的去污效果，但在MP生菜的情况下则没有。气态ClO₂未能延长MP生菜和MP卷心菜的保质期，应研究去污样品中微生物生长增强的原因。尽管如此，我们的结果证明可以抑制ClO₂引起的褐变。
