Evaluation of the Potential of Lactobacillus paracasei Adjuncts for Flavor Compounds Development and Diversification in Short-Aged Cheddar Cheese.

Ewelina Stefanovic,Clara Roces,Jeremiah J Sheehan,Mary C Rea,Maurice O'Sullivan,Kieran N Kilcawley,Olivia Mcauliffe

doi:10.3389/fmicb.2018.01506

Abstract

The non-starter microbiota of Cheddar cheese mostly comprises mesophilic lactobacilli, such as Lactobacillus casei, Lactobacillus paracasei, Lactobacillus rhamnosus, and Lactobacillus plantarum. These bacteria are recognized for their potential to improve Cheddar cheese flavor when used as adjunct cultures. In this study, three strains of L. paracasei (DPC2071, DPC4206, and DPC4536) were evaluated for their contribution to the enhancement and diversification of flavor in short-aged Cheddar cheese. The strains were selected based on their previously determined genomic diversity, variability in proteolytic enzyme activities and metabolic capability in cheese model systems. The addition of adjunct cultures did not affect the gross composition or levels of lipolysis of the cheeses. The levels of free amino acids (FAA) in cheeses showed a significant increase after 28 days of ripening. However, the concentrations of individual amino acids in the cheeses did not significantly differ except for some amino acids (aspartic acid, threonine, serine, and tryptophan) at Day 14. Volatile profile analysis revealed that the main compounds that differentiated the cheeses were of lipid origin, such as long chain aldehydes, acids, ketones, and lactones. This study demonstrated that the adjunct L. paracasei strains contributed to the development and diversification of compounds related to flavor in short-aged Cheddar cheeses.

Highlights

The production of cheese globally increases year-on-year with an annual production of over 22 million tons
The use of Pulsed Field Gel Electrophoresis (PFGE) profiles as an indicator of the presence of individual strains revealed that in each test cheese, at the end of ripening the patterns of non-starter lactic acid bacteria (NSLAB) dominating at the highest dilution corresponded to the patterns of inoculated adjunct in each of the vats (Figure 2A)
In bacterial-ripened cheeses, such as Cheddar, the dynamic evolution of both the starter and non-starter microbial populations depends on environmental conditions and available nutrients during the manufacture and ripening affecting acidification, biochemical transformation of substrates and flavor development (Bautista-Gallego et al, 2014)

Summary

Introduction

The production of cheese globally increases year-on-year with an annual production of over 22 million tons (www.dairy.ahdb.org, report from February 27th, 2017). With such a high market demand, the dairy industry is challenged by increasing consumer requirements for products of novel flavor. Proteolytic reactions that occur during cheese manufacture and ripening are seen as major contributors to texture and flavor development (McSweeney and Sousa, 2000). In the glycolytic/citrate pathway, pyruvate represents the central metabolite occurring from lactose or citrate metabolism, and it is further degraded to acetaldehyde, ethanol, diacetyl, and acetoin, all of which are important cheese flavor contributors (Marilley and Casey, 2004). Since microorganisms present in cheese during the ripening differ in their metabolic abilities, the alteration of the microbial populations in the cheese represents a potential tool for flavor diversification (Van Hoorde et al, 2010)

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