Nonstarter lactic acid bacteria volatilomes produced using cheese components

Abstract

In long-ripened cheese, flavor formation occurs during ripening. The metabolism of lactic acid bacteria (LAB) leads to the production of different compounds that contribute to the flavor of cheese. The contribution of LAB to the formation of cheese flavor has previously been studied. However, the specific nonstarter LAB (NSLAB) metabolic reactions in ripened cheese that lead to the formation of flavor compounds remain unclear. In ripened cheese, the nutrient sources available include small peptides or amino acids, citrate, lactate, free fatty acids, and starter LAB cell lysis products. Thus, the aim of this study was to evaluate the ability of NSLAB to produce volatile flavor compounds by using an in vitro system that used only the nutrients available in ripened cheese as the energy source. Moreover, the potential contribution of the NSLAB volatilome on total cheese flavor is discussed. For this purpose, the production of volatile compounds on cheese-based medium (CBM) and on starter LAB lysed cell medium (LCM) by 2 Lactobacillus casei and 2 Lactobacillus rhamnosus strains, previously isolated from ripened Parmigiano Reggiano cheese, was investigated. The generated volatile compounds were analyzed with head-space gas chromatography mass spectrometry. Overall, ketones, aldehydes, alcohols, and acids were the most abundant compounds produced. Differences in volatilome production were found between NSLAB grown in LCM and CBM. The catabolic metabolism of amino acids and fatty acids were required for NSLAB growth on LCM. Conversely, pyruvate metabolism was the main catabolic pathway that supported growth of NSLAB in CBM. This study can be considered a first step toward a better understanding of how microbiota involved in the long ripening of cheese may contribute to the development of cheese flavor.

The individual contribution of starter and non-starter lactic acid bacteria to the volatile organic compound composition of Caciocavallo Palermitano cheese

“…The initial levels of the strains ranged between 5.24 and 6.73 log CFU/mL. All strains showed a clear growth in CBM indicating the suitability of this synthetic medium to perform the evaluation of the VOCs profile of single strains confirming the previous observations of Sgarbi et al (2013). In general, the most consistent development was registered for NSLAB strains with L. rhamnosus FMAC240, P. pentosaceus FMAC67, E. durans FMAC134B and E. faecalis FMA721 showing an increase of about 2 orders of magnitude.…”

“…The cheese suspension was centrifuged at 8000 rpm × 15 min and filtered through sterile cotton gauze to remove surfaced fat layer and, after that, the resulting solution was sterilized for 15 min at 121°C. Cell suspensions were inoculated (1% v/v) in vials (20 mL volume) containing 5 mL of CBM (Sgarbi et al, 2013). The vials were sealed with parafilm to avoid the dispersion of VOCs and incubated anaerobically in hermetic jars added with the AnaeroGen AN25 system (Oxoid) for 4 d at 30 and 44°C for NSLAB and SLAB, respectively.…”

“…Most of these studies focused on the metabolic capabilities and the generation of VOCs with clear flavor descriptors of LAB, mainly SLAB such as Lactococcus lactis, Lactobacillus delbrueckii and Streptococcus thermophilus (Marilley and Casey, 2004;Morales et al, 2003;Randazzo et al, 2008). Recently, the contribution of NSLAB to the aroma of ripened cheeses has been object of a few studies (Bezerra et al, 2016;Lazzi et al, 2016;Sgarbi et al, 2013). In particular, Sgarbi et al (2013) determined the VOCs generated by single strains of NSLAB in a synthetic medium that simulated a cheese environment, namely CBM.…”

“…Recently, the contribution of NSLAB to the aroma of ripened cheeses has been object of a few studies (Bezerra et al, 2016;Lazzi et al, 2016;Sgarbi et al, 2013). In particular, Sgarbi et al (2013) determined the VOCs generated by single strains of NSLAB in a synthetic medium that simulated a cheese environment, namely CBM. In that study, two strains of L. casei and two strains of L. rhamnosus, which dominate the NSLAB population during ripening of Parmesan cheese, where investigated.…”

Isolation and identification of lactic acid bacteria from Brazilian Minas artisanal cheese

“…The Lactobacilli constitute a major group of LAB and comprise a wide range of niches. They play an important role during ripening of industrial and artisanal cheeses, as they produce volatile flavor compounds that contribute to their sensory profile (Sgarbi et al, 2013). Among the identified isolates, the most frequent LAB species recovered from cheese in the rainy season belonged to the species L. plantarum and L. brevis, while in the dry season, the most frequent LAB belonged to the L. rhamnosus species.…”