Department of Food Science and Technology, Texas A&M University, College Station, Texas, USA.
Department of Biological and Agricultural Engineering, Texas A&M University, College Station, Texas, USA.
J Food Sci. 2022 Oct;87(10):4649-4664. doi: 10.1111/1750-3841.16294. Epub 2022 Aug 31.
This study synthesized and characterized ZIF-8 nanoparticles encapsulated with trans-cinnamaldehyde oil (TC) and evaluated their antimicrobial effectiveness against Escherichia coli O157:H7 on fresh spinach leaves. The antimicrobial activity of different mass ratios of TC-encapsulated ZIF-8 against E. coli O157:H7 (ATCC 43895) strain was assessed and the best mass ratio of 1:2 TC to ZIF-8 identified. Spinach leaves were treated with (1) 0.5TC@ZIF-8_PL nanoparticle complexes solution, (2) 200 ppm chlorine, (3) free TC, and (4) sterilized distilled water (control). All sample groups were rinsed for 1 min, dried in a biosafety cabinet, weighted, and packed in sterilized Whirl-pk Stand-Up sampling bags, and stored at 4°C for 15 days for shelf life studies. Samples were dipped into a solution of nanoparticles and another group was sprayed. The quality of spinach samples was assessed by monitoring changes in moisture content (MC), water activity (Aw), color, pH, texture (firmness and work), vitamin C content, total carotenoid, and chlorophyll content. Spinach leaves treated with 0.5TC@ZIF-8_PL had less (p < 0.05) water, total chlorophyll, and total carotenoid losses, with minimal changes in pH. However, treatment did not prevent the color degradation (p > 0.05) and adversely affected spinach firmness. The spinach samples treated with 200 ppm chlorine and free TC had higher (p < 0.05) total chlorophyll degradation than the samples treated with the nanoparticles. The mass ratio of TC-encapsulated ZIF-8 must be readjusted to reduce potential toxicity issues while maintaining the antimicrobial properties. PRACTICAL APPLICATION: Zeolitic imidazolate framework-8 (ZIF-8) nanoparticle complex can be used to encapsulate natural antimicrobials to inhibit growth of pathogens on fresh produce. A 2-log reduction in populations of Escherichia coli O157:H7 on fresh spinach leaves was achieved using trans-cinnamaldehyde at low concentrations. The results can be used to embed the compounds into polymeric films for antimicrobial packaging applications.
本研究合成并表征了负载肉桂醛油的 ZIF-8 纳米粒子，并评估了其在新鲜菠菜叶片上对大肠杆菌 O157:H7 的抗菌效果。评估了不同质量比的负载肉桂醛的 ZIF-8 对大肠杆菌 O157:H7（ATCC 43895）菌株的抗菌活性，并确定了最佳质量比为 1:2TC 与 ZIF-8。用（1）0.5TC@ZIF-8_PL 纳米粒子复合物溶液、（2）200ppm 氯、（3）游离肉桂醛和（4）消毒蒸馏水（对照）处理菠菜叶片。所有样品组均用溶液冲洗 1 分钟，在生物安全柜中干燥，称重，装入消毒的 Whirl-pk 站立式采样袋中，在 4°C 下储存 15 天进行货架期研究。将样品浸入纳米粒子溶液中，另一组进行喷雾处理。通过监测水分含量 (MC)、水分活度 (Aw)、颜色、pH 值、质地（硬度和工作性）、维生素 C 含量、总类胡萝卜素和叶绿素含量的变化来评估菠菜样品的质量。用 0.5TC@ZIF-8_PL 处理的菠菜叶片的水分、总叶绿素和总类胡萝卜素损失较少（p<0.05），pH 值变化最小。然而，处理并不能防止颜色降解（p>0.05），并且对菠菜的硬度产生不利影响。用 200ppm 氯和游离肉桂醛处理的菠菜样品的总叶绿素降解率高于用纳米粒子处理的样品（p<0.05）。必须调整负载肉桂醛的 ZIF-8 的质量比，以减少潜在的毒性问题，同时保持抗菌性能。实际应用：沸石咪唑酯骨架-8（ZIF-8）纳米粒子复合物可用于封装天然抗菌剂，以抑制新鲜农产品上病原体的生长。在新鲜菠菜叶片上，使用低浓度的肉桂醛可实现大肠杆菌 O157:H7 数量减少 2 个对数级。研究结果可用于将化合物嵌入聚合物薄膜中，以实现抗菌包装应用。
