Food Biotechnology & Innovation group, International Joint Research Laboratory, Tropical Bioresources & Biotechnology, Univ. Bourgogne Franche-Comté, AgroSup Dijon, PAM UMR A 02.102 and School of Biotechnology and Food Technology, Hanoi University of Science and Technology, Dijon, France; Faculty of Chemical and Food Engineering, Institute of Technology of Cambodia, Russian Federation Blvd., P.O. Box 86, 12156 Phnom Penh, Cambodia; Tropical Fermentation Network, France.
Food Biotechnology & Innovation group, International Joint Research Laboratory, Tropical Bioresources & Biotechnology, Univ. Bourgogne Franche-Comté, AgroSup Dijon, PAM UMR A 02.102 and School of Biotechnology and Food Technology, Hanoi University of Science and Technology, Dijon, France; Tropical Fermentation Network, France.
Int J Food Microbiol. 2021 Jul 16;350:109242. doi: 10.1016/j.ijfoodmicro.2021.109242. Epub 2021 May 11.
Lactic acid fermentation is a traditional process to preserve foods and to modify their organoleptic properties. This process is generally conducted in a spontaneous way, allowing indigenous lactic acid bacteria (LAB) of the matrix and of the environment to compete and grow. The aim of this study was to better characterise LAB strains ability to modify aroma profiles in fruit and vegetable matrices, by focusing on two key enzymatic activities: β-glucosidase and alcohol dehydrogenase (ADH). Firstly, 200 LAB isolated from Cambodian and Vietnamese fermented foods were screened for their β-glucosidase activity and duplicate isolates identified through RAPD-PCR analysis were discarded. Thereby, 40 strains were found positive for β-glucosidase using p-nitrophenyl-β-D-glucopyranoside as substrate. Among them, 14 displayed an activity greater than 10 nmol/min/mg dry cell. Thirteen were identified as Lactiplantibacillus (L.) plantarum and one as L. pentosus. Secondly, four strains of different phenotypes for β-glucosidase activity were tested for ADH activity. The highest reduction ability for hexanal and (E)-2-hexenal was obtained for Limosilactobacillus (L.) fermentum V013-1A for which no β-glucosidase activity was detectable. The three other strains (L. plantarum C022-2B, C022-3B, and V0023-4B2) exhibited a lower reduction ability and only for hexanal. Thirdly, mashed tomatoes were fermented with these four strains individually to evaluate their ability to release volatile compounds from the tomato precursors. Fifty-eight volatile compounds were identified and quantified by HS-SPME/GC-MS. Untreated tomatoes were rich in aldehydes. The tomatoes fermented with L. plantarum strains were rich in ketones whereas those with L. fermentum were rich in alcohols. However, for the generation of terpenoids that provide flower and fruit flavours, our screening of β-glucosidase activity was not able to explain the differences among the strains. For ADH activity, L. fermentum exhibited a high activity in fermentation as most of the target aldehydes and ketones disappeared and were replaced by their corresponding alcohols. The L. plantarum strains exhibited a lower activity but with an important substrate-selectivity diversity. A better knowledge of the functionality of each LAB strain in the food matrix will permit to predict and shape the aroma profiles of fermented food.
乳酸发酵是一种传统的保存食物和改变其感官特性的方法。这个过程通常是自发进行的，允许基质和环境中的土著乳酸菌（LAB）竞争和生长。本研究的目的是更好地描述 LAB 菌株在水果和蔬菜基质中改变香气特征的能力，重点关注两种关键的酶活性：β-葡萄糖苷酶和醇脱氢酶（ADH）。首先，从柬埔寨和越南发酵食品中筛选了 200 株 LAB，以检测其β-葡萄糖苷酶活性，并通过 RAPD-PCR 分析剔除重复的分离株。结果发现，有 40 株使用 p-硝基苯-β-D-葡萄糖苷作为底物时表现出β-葡萄糖苷酶活性。其中，有 14 株的活性大于 10 nmol/min/mg 干细胞。13 株被鉴定为植物乳杆菌（L.）植物乳杆菌，1 株被鉴定为戊糖片球菌（L.）pentosus。其次，测试了 4 株不同表型的β-葡萄糖苷酶活性菌株的 ADH 活性。对于 Limosilactobacillus（L.）fermentum V013-1A，检测到最高的己醛和（E）-2-己烯醛还原能力，而该菌株检测不到β-葡萄糖苷酶活性。其他 3 株（L.）plantarum C022-2B、C022-3B 和 V0023-4B2 的还原能力较低，仅对己醛有还原能力。第三，用这 4 株菌单独发酵番茄泥，以评估它们从番茄前体中释放挥发性化合物的能力。采用 HS-SPME/GC-MS 共鉴定和定量了 58 种挥发性化合物。未经处理的番茄富含醛类。用植物乳杆菌菌株发酵的番茄富含酮类，而用发酵乳杆菌发酵的番茄富含醇类。然而，对于生成提供花香和果香的萜类化合物，我们对β-葡萄糖苷酶活性的筛选并不能解释菌株间的差异。对于 ADH 活性，L. fermentum 在发酵过程中表现出很高的活性，因为大多数目标醛类和酮类都消失了，被相应的醇类所取代。L.）plantarum 菌株的活性较低，但具有重要的底物选择性多样性。更好地了解每种 LAB 菌株在食品基质中的功能将有助于预测和塑造发酵食品的香气特征。
