Chuang Shihyu, Ghoshal Mrinalini, McLandsborough Lynne
Department of Food Science, University of Massachusetts, Amherst, MA, United States.
Department of Microbiology, University of Massachusetts, Amherst, MA, United States.
Front Microbiol. 2023 Jun 12;14:1197473. doi: 10.3389/fmicb.2023.1197473. eCollection 2023.
Sanitizing low-moisture food (LMF) processing equipment is challenging due to the increased heat resistance of spp. in low-water activity (a) environments. Food-grade oils mixed with acetic acid have been shown effective against desiccated . In this study, different hydrocarbon chain-length (C) organic acids were tested against desiccated by using 1% v/v water-in-oil (W/O) emulsion as the delivery system for 200 mM acid. Fluorescence lifetime imaging microscopy (FLIM) was utilized with a BODIPY-based molecular rotor to evaluate membrane viscosity under environmental conditions such as desiccation and temperature elevation. Drying hydrated cells to 75% equilibrium relative humidity (ERH) increased the membrane viscosity from 1,199 to 1,309 mPa·s (cP) at 22°C. Heating to 45°C decreased the membrane viscosity of hydrated cells from 1,199 to 1,082 mPa·s, and decreased that of the desiccated cells from 1,309 to 1,245 mPa·s. At both 22°C and 45°C, desiccated was highly susceptible (>6.5 microbial log reduction (MLR) per stainless-steel coupon) to a 30-min treatment with the W/O emulsions formulated with short carbon chain acids (C). By comparison, the emulsion formulations with longer carbon chain acids (C) showed little to no MLR at 22°C, but achieved >6.5 MLR at 45°C. Based upon the decreased membrane viscosity and the increased antimicrobial efficacy of C W/O emulsions with increasing temperature, we propose that heating can make the membrane more fluid which may allow the longer carbon chain acids (C) to permeate or disrupt membrane structures.
由于在低水分活度（a）环境中，某些菌种的耐热性增强，对低水分食品（LMF）加工设备进行消毒具有挑战性。已证明与乙酸混合的食品级油对干燥的（相关菌种）有效。在本研究中，使用1% v/v油包水（W/O）乳液作为200 mM酸的递送系统，测试了不同碳链长度（C）的有机酸对干燥的（相关菌种）的效果。利用基于BODIPY的分子转子的荧光寿命成像显微镜（FLIM）来评估在干燥和温度升高等环境条件下的膜粘度。将水合（相关菌种）细胞干燥至75%平衡相对湿度（ERH），在22°C时膜粘度从1199增加到1309 mPa·s（厘泊）。加热到45°C使水合细胞的膜粘度从1199降低到1082 mPa·s，并使干燥细胞的膜粘度从1309降低到1245 mPa·s。在22°C和45°C时，干燥的（相关菌种）对用短碳链酸（C）配制的W/O乳液处理30分钟高度敏感（每个不锈钢试片微生物对数减少（MLR）>6.5）。相比之下，用长碳链酸（C）配制的乳液制剂在22°C时几乎没有MLR，但在45°C时实现了>6.5 MLR。基于膜粘度降低以及随着温度升高C W/O乳液抗菌效果增强，我们提出加热可使膜更具流动性，这可能使长碳链酸（C）渗透或破坏膜结构。
