Volatile Molecule Profiles and Anti-Listeria monocytogenes Activity of Nisin Producers Lactococcus lactis Strains in Vegetable Drinks.

Lorenzo Siroli,Francesca Patrignani,Maria Barbara Pisano,Lucia Camprini,Rosalba Lanciotti

doi:10.3389/fmicb.2019.00563

Abstract

This work aimed to evaluate the potential of 15 nisin producing Lactococcus lactis strains, isolated from dairy products, for the fermentation of soymilk and carrot juice. In particular, the acidification and the production of nisin in the food matrices were recorded. Moreover, three strains (LBG2, FBG1P, and 3LC39), that showed the most promising results were further scrutinized for their anti-Listeria monocytogenes activity and volatile molecules profile during fermentation of soymilk and carrot juice. Lactococcus lactis strains LBG2, FBG1P, and 3LC39 resulted the most interesting ones, showing rapid growth and acidification on both food matrices. The higher amounts of nisin were detected in soymilk samples fermented by the strain LBG2 after 24 and 48 h (26.4 mg/L). Furthermore, the rapid acidification combined with the production of nisin resulted in a strong anti-Listeria activity, reducing the pathogen loads below the detection limit, in carrot juice samples fermented by the strains LBG2 and FBG1P and in soymilk by the strain LBG2. The fermentation increased the presence of volatile molecules such as aldehydes and ketones with a positive impact on the organoleptic profile of both the fermented products. These results highlighted the interesting potential of three nisin producing L. lactis strains for the production of fermented carrot juice and soymilk. In fact, the fermentation by lactic acid bacteria, combined or not with other mild technologies, represents a good strategy for the microbiological stabilization of these products. Furthermore, the increase of molecules with a positive sensory impact, such as aldehydes and ketones, in the fermented products suggests a possible improvement of their organoleptic characteristics.

Highlights

Vegetable beverages are perceived by consumers as “healthy” foods because of their low content of sodium, cholesterol, fat and because they are rich in vitamin C, polyphenols and flavonoids that contribute to the good antioxidant properties of these products (Kumar et al, 2009; Patrignani et al, 2009)
In the first step of the study, the capability to grow, acidify and produce nisin, of the 15 nisin producer L. lactis strains, was evaluated in two different food matrices such as soymilk and carrot juice characterized by different composition and pH-values
The results obtained highlighted the interesting properties of different strains of L. lactis as fermenting agents of soymilk and carrot juice

Summary

Introduction

Vegetable beverages are perceived by consumers as “healthy” foods because of their low content of sodium, cholesterol, fat and because they are rich in vitamin C, polyphenols and flavonoids that contribute to the good antioxidant properties of these products (Kumar et al, 2009; Patrignani et al, 2009). For these reasons, their market is increased in recent years (Kregiel, 2015). Soy-based foods have received increased attention in healthconscious societies, especially in Western countries, due to their reported beneficial effects on menopausal symptoms and metabolic-related diseases (Cao et al, 2018)

Objectives

Methods

Results

Discussion

Conclusion