Liao C H, Fett W F
U.S. Department of Agriculture, Agricultural Research Service, Eastern Regional Research Center, Wyndmoor, Pennsylvania 19038, USA.
J Food Prot. 2001 Aug;64(8):1110-5. doi: 10.4315/0362-028x-64.8.1110.
The native microflora of three types of produce (green bell peppers, Romaine lettuce, and prepeeled baby carrots) and two types of sprouting seeds (alfalfa and clover) were investigated. Aerobic plate count (APC) for each produce or seed type as determined on Pseudomonas agar F (PAF) with incubation at 28 degrees C was in the range of 4 to 7 log CFU per g of tissue or seed. There was no significant difference (P > or = 0.05) in APC when the determinations were made with three agar media including PAF, brain heart infusion agar, and plate count agar. However, the APC as determined from plates that were incubated at 28 degrees C was significantly (P < or = 0.05) higher than with incubation at 37 degrees C. Fluorescent pseudomonads accounted for 23 to 73% of APC and 6 to 18% of APC recovered from carrots, pepper, and lettuce were pectolytic. Forty-eight strains of pectolytic bacteria were randomly isolated and identified, respectively, as members of the genera of Pseudomonas, Erwinia, Bacillus, Xanthomonas, or Flavobacterium. Lactic acid bacteria and/or yeast were consistently isolated from baby carrots, lettuce, and sprouting seeds (alfalfa or clover) but not from green bell peppers. Approximately 120 strains of indigenous microflora were tested for their ability to inhibit the growth of Salmonella Chester, Listeria monocytogenes, Escherichia coli, or Erwinia carotovora subsp. carotovora on PAF. Six isolates capable of inhibiting the growth of at least one pathogen were isolated and identified, respectively, as Bacillus spp. (three strains), Pseudomonas aeruginosa (one strain), Pseudomonas fluorescens (strain A3), and yeast (strain D1). When green pepper disks were inoculated with strains A3 and D1, the growth of Salmonella Chester and L. monocytogenes on the disks was reduced by 1 and 2 logs, respectively, over a period of 3 days. Application of strains A3 and D1 as potential biopreservatives for enhancing the quality and safety of fresh produce is discussed.
对三种农产品（青椒、长叶生菜和去皮小胡萝卜）以及两种发芽种子（苜蓿和三叶草）的原生微生物区系进行了研究。在28℃下于假单胞菌琼脂F（PAF）上测定的每种农产品或种子类型的需氧平板计数（APC）为每克组织或种子4至7 log CFU。当使用包括PAF、脑心浸液琼脂和平板计数琼脂在内的三种琼脂培养基进行测定时，APC没有显著差异（P≥0.05）。然而，在28℃下培养的平板所测定的APC显著（P≤0.05）高于在37℃下培养的平板。荧光假单胞菌占APC的23%至73%，从胡萝卜、辣椒和生菜中回收的APC中有6%至18%是果胶分解菌。随机分离并鉴定了48株果胶分解菌，分别属于假单胞菌属、欧文氏菌属、芽孢杆菌属、黄单胞菌属或黄杆菌属。始终能从去皮小胡萝卜、生菜和发芽种子（苜蓿或三叶草）中分离出乳酸菌和/或酵母菌，但从青椒中未分离出。对大约120株原生微生物区系菌株抑制切斯特沙门氏菌、单核细胞增生李斯特菌、大肠杆菌或胡萝卜软腐欧文氏菌胡萝卜亚种在PAF上生长的能力进行了测试。分离并鉴定出6株能够抑制至少一种病原体生长的菌株，分别为芽孢杆菌属（3株）、铜绿假单胞菌（1株）、荧光假单胞菌（A3菌株）和酵母菌（D1菌株）。当用A3菌株和D1菌株接种青椒圆片时，在3天的时间里，切斯特沙门氏菌和单核细胞增生李斯特菌在圆片上的生长分别减少了1 log和2 log。讨论了将A3菌株和D1菌株用作潜在生物防腐剂以提高新鲜农产品质量和安全性的应用。
