NIZO food research, Kernhemseweg 2, 6718 ZB Ede, the Netherlands; Wageningen University and Research, Food Microbiology, P.O. Box 17, 6700 AA Wageningen, the Netherlands.
NIZO food research, Kernhemseweg 2, 6718 ZB Ede, the Netherlands.
Int J Food Microbiol. 2023 Dec 16;407:110392. doi: 10.1016/j.ijfoodmicro.2023.110392. Epub 2023 Sep 9.
In this study levels and types of microbial contaminants were investigated in 88 different plant-based ingredients including many that are used to manufacture dairy alternatives. Studied ingredients encompassed samples of pulses (pea, faba bean, chickpea, and mung bean), cereals/pseudocereals (oat, rice, amaranth and quinoa) and drupes (coconut, almond and cashew). The microbial analysis included: i) total viable count (TVC), ii) total aerobic mesophilic spore count (TMS), iii) heat resistant aerobic thermophilic spore count (HRTS), iv) anaerobic sulfite reducing Clostridium spore count (SRCS), and v) Bacillus cereus spore count (BCES). Microorganisms isolated from the counting plates with the highest sample dilutions were identified using 16S rRNA and MALDI-TOF MS analyses. Many of the investigated ingredients showed a high proportion of spores as part of their total aerobic mesophilic counts. In 63 % of the samples, the difference between TVC and TMS counts was 1 Log unit or less. This was particularly the case for the majority of pea isolates and concentrates, faba bean isolates, oat kernels and flakes, and for single samples of chickpea isolate, almond, amaranth, rice, quinoa, and coconut flours. Concentrations of TVC ranged between <1.0 and 5.3 Log CFU/g in different samples, and TMS varied between <1.0 and 4.1 Log CFU/g. Levels of HTRS, BCES and SRCS were generally low, typically around or below the LOD of 1.0 Log CFU/g. In total, 845 individual bacterial colonies were isolated belonging to 33 different genera. Bacillus licheniformis and B. cereus group strains were most frequently detected among Bacillus isolates, and these species originated primarily from pea and oat samples. Geobacillus stearothermophilus was the main species encountered as part of the HRTS. Among the Clostridium isolates, Clostridum sporogenes/tepidum were predominant species, which were mostly found in pea and almond samples. Strains with potential to cause foodborne infection or intoxication were typed using the PCR-based method for toxin genes detection. In the B. cereus group, 9 % of isolates contained the ces gene, 28 % contained hbl, 42 % cytK, and 69 % were positive for the nhe gene. Absence of the boNT-A and -B genes was confirmed for all isolated C. sporogenes/tepidum strains. Nearly all (98 %) B. licheniformis isolates were positive for the lchAA gene. Insight into the occurrence of microbial contaminants in plant-based ingredients, combined with knowledge of their key inactivation and growth characteristics, can be used for the microbial risk assessment and effective design of plant-based food processing conditions and formulations to ensure food safety and prevent spoilage.
在这项研究中，研究了 88 种不同植物性成分中的微生物污染物的水平和类型，其中包括许多用于制造乳制品替代品的成分。研究成分包括豆类（豌豆、蚕豆、鹰嘴豆和绿豆）、谷物/假谷物（燕麦、大米、苋菜和藜麦）和核果（椰子、杏仁和腰果）的样本。微生物分析包括：i）总活菌计数（TVC），ii）总需氧嗜温孢子计数（TMS），iii）耐热需氧嗜热孢子计数（HRTS），iv）厌氧亚硫酸盐还原梭菌孢子计数（SRCS），和 v）蜡样芽孢杆菌孢子计数（BCES）。使用 16S rRNA 和 MALDI-TOF MS 分析从计数平板中分离出的最高稀释度的微生物。许多研究成分的总需氧嗜温计数中都有很高比例的孢子。在 63%的样本中，TVC 和 TMS 计数之间的差异为 1 个对数单位或更小。这种情况尤其适用于大多数豌豆分离株和浓缩物、蚕豆分离株、燕麦仁、燕麦片以及豌豆分离株、杏仁、苋菜、大米、藜麦和椰子粉的单一样本。不同样品中 TVC 的浓度范围在<1.0 到 5.3 Log CFU/g 之间，TMS 浓度范围在<1.0 到 4.1 Log CFU/g 之间。HTRS、BCES 和 SRCS 的水平通常较低，通常在 1.0 Log CFU/g 左右或以下。总共分离出 845 个细菌菌落，属于 33 个不同的属。蜡样芽孢杆菌和芽孢杆菌属群菌株是芽孢杆菌属分离株中最常检测到的菌株，这些菌株主要来自豌豆和燕麦样本。作为 HRTS 的一部分，发现主要是嗜热脂肪地芽孢杆菌。在梭菌属分离株中，凝结芽孢杆菌/温和芽孢杆菌是主要的种，主要存在于豌豆和杏仁样本中。使用基于 PCR 的毒素基因检测方法对具有潜在食源性感染或中毒能力的菌株进行分型。在芽孢杆菌属群中，9%的分离株含有 ces 基因，28%含有 hbl，42%含有 cytK，69%含有 nhe 基因。所有分离的凝结芽孢杆菌/温和芽孢杆菌菌株均未检出 boNT-A 和 -B 基因。几乎所有（98%）的蜡样芽孢杆菌分离株都含有 lchAA 基因。了解植物性成分中微生物污染物的存在情况，并结合其关键失活和生长特性的知识，可用于微生物风险评估和有效设计植物性食品加工条件和配方，以确保食品安全和防止变质。
