Matching starter phenotype to functionality for low salt Cheddar cheese production based on viability, permeability, autolysis, enzyme accessibility and release in model systems
Introduction
Demand for lower salt cheeses is increasing with greater awareness of adverse health implications of excessive sodium intake (He & MacGregor, 2009). However, development of such cheeses poses challenges as salt impacts final quality (Guinee and Fox, 2004, Johnson et al., 2009). Salt addition during cheese manufacture promotes whey expulsion, ensures typical composition and depresses water activity (aw) (Guinee, 2004, Johnson et al., 2009). Salt also influences starter lactic acid bacteria (LAB) permeabilisation and/or autolysis, which are essential for flavour development (Bunthof et al., 2001, Sheehan et al., 2005).
LAB significantly influence flavour development (Stanley, 2003) as they possess a complex proteolytic system including cell wall bound proteinases and intracellular peptidases (Ruggirello et al., 2016, Thomas and Pritchard, 1987) that hydrolyse chymosin-derived peptides to flavourful low molecular weight peptides and free amino acids (FAA) (Bachmann et al., 2009, Børsting et al., 2015, Leroy and De Vuyst, 2004, Lortal and Chapot-Chartier, 2005, Savijoki et al., 2006). As many peptidases are intracellular, permeabilisation and autolysis are needed for release into cheese (Doolan and Wilkinson, 2009, Sheehan et al., 2005). Increased permeabilisation and autolysis enhances enzyme release, positively influences flavour and reduces bitterness (Guldfeldt et al., 2001, Hickey et al., 2018, Hickey et al., 2007, Sheehan et al., 2005). The limited data available suggest this relationship may be strain-dependent and influenced by composition (Chapot-Chartier et al., 1994, Sheehan et al., 2006).
A key technical issue in low-salt Cheddar cheese manufacture is the downstream effect of higher moisture and lower salt in moisture (S/M) levels on the dynamics of ripening (McCarthy et al., 2015, McMahon et al., 2014). Higher moisture and lower S/M levels (McCarthy et al., 2015) are linked to higher starter viability, higher CEP activity, which, when combined with insufficient autolysis, leads to bitterness (Broadbent et al., 2002, Mistry, 2001).
Traditionally, starters are selected for acid production, phage resistance, temperature and salt sensitivity and appropriate flavour. However, some of the above may not be the most relevant selection criteria for low salt cheese production (Johnson, 2014, Powell et al., 2011, Stanley, 2003). Starter selection for altered cheese environments requires additional criteria including low viability and higher sensitivity to reduced salt levels with permeabilisation, autolysis, intracellular enzyme accessibility and release similar to full-salt cheese. This study assessed six starter strains in model systems to select the most suitable strains, based on the above criteria, for production of Cheddar cheese with reduced salt content.
Section snippets
Bacterial strains and culture conditions
Six well known reference cheesemaking strains, five Lactococcus lactis subsp. cremoris strains and one L. lactis subsp. lactis strain were examined at 0%, 3% and 5% (w/v) NaCl in 10% (w/v) reconstituted skim milk (RSM) (Oxoid, Bedfordshire, UK) model systems. L. lactis subsp. cremoris AM2, SK11, HP and R1 were obtained from the NCIMB bacterial culture collection (NCIMB Ltd., Aberdeen, UK), while L. lactis subsp. cremoris Z8 and L. lactis subsp. lactis 303 were obtained from the culture
Water activity
Similar aw levels (∼0.991) were noted in all systems prior to salting (Tps), and decreased significantly depending on the level of added salt (Tas) to reach ∼0.991, 0.977 or 0.967 at 0%, 3% or 5% (w/v) NaCl, respectively (Fig. 1). Storage time had no significant influence on aw.
Effect of salt and storage time on the viability of starter strains in model systems
Populations at (T0) were 6.0, 6.7, 6.6, 7.3, 7.4 and 6.5 log cfu mL−1 for AM2, SK11, Z8, HP, 303 or R1, respectively. Strains 303 and HP had highest initial viability compared with AM2, SK11, Z8 or R1, which had a one
Discussion
LAB starters have been studied at the genome level in simulated cheese microenvironments (Desfosses-Foucault et al., 2014, Ruggirello et al., 2016, Taibi et al., 2011) while at the phenotype level, Bachmann et al. (2009) and Boutrou, Sepulchre, and Monnet (1998) examined autolysis and proteolysis in buffer, pseudo curd and microplate cheese systems. However, a new approach may enable additional criteria to be used for selection of starters for manufacture of low salt Cheddar cheese including
Conclusions
Salt sensitivity of strains AM2, SK11 and Z8 can compensate for deficiencies in autolysis, PepX release and CEP activities at lower salt levels. Strains AM2 and SK11 contained significant permeabilised cells at all salt levels allowing release of de-bittering peptidases and a possible reduction in CEP generated bitter peptides. Accessibility to intracellular PepX appears strain-dependent and triggered by a strain-related cook temperature response. The relationship between salt, permeabilisation
Acknowledgements
This work was funded by the Department of Agriculture, Fisheries and the Marine (DAFM), (10/RD/CheeseBoard2015/TMFRC/704), under the Food Institutional Research Measure (FIRM). GL and MW would also like to thank the NSERC/DFO Industrial Research Chair in Dairy Microbiology for funding support.
References (55)
- et al.
A high-throughput cheese manufacturing model for effective cheese starter culture screening
Journal of Dairy Science
(2009) - et al.
Influence of proteolytic Lactococcus lactis subsp. cremoris on ripening of reduced-fat Cheddar cheese made with camel chymosin
International Dairy Journal
(2015) - et al.
Simple tests for predicting the lytic behavior and proteolytic activity of lactococcal strains in cheese
Journal of Dairy Science
(1998) - et al.
Assessment of wild non-dairy lactococcal strains for flavour diversification in a mini-Gouda type cheese model
Food Research International
(2014) - et al.
Autolysis of two strains of Lactococcus lactis during cheese ripening
International Dairy Journal
(1994) - et al.
Comparison of subcellular fractionation methods for Lactococcus lactis subsp. lactis and L. lactis subsp. cremoris
International Dairy Journal
(1993) - et al.
Transcription profiling of interactions between Lactococcus lactis subsp. cremoris SK11 and Lactobacillus paracasei ATCC334 during Cheddar cheese simulation
International Journal of Food Microbiology
(2014) - et al.
Comparison of the effects of various attenuation methods on cell permeability and accessibility of intracellular enzymes in Lactococcus lactis strains
International Dairy Journal
(2009) - et al.
Isolation of Streptococcus lactis C2 mutants selected for temperature sensitivity and potential use in cheese manufacture
Journal of Dairy Science
(1987) - et al.
Effect of starter cultures with a genetically modified peptidolytic or lytic system on Cheddar cheese ripening
International Dairy Journal
(2001)
Redefining the effect of salt on thermophilic starter cell viability, culturability and metabolic activity in cheese
Food Microbiology
Lactic acid bacteria as functional starter cultures for the food fermentation industry
Trends in Food Science & Technology
Role, mechanisms and control of lactic acid bacteria lysis in cheese
International Dairy Journal
Symposium review: Lactococcus lactis from nondairy sources: Their genetic and metabolic diversity and potential applications in cheese
Journal of Dairy Science
Effect of sodium, potassium, magnesium, and calcium salt cations on pH, proteolysis, organic acids, and microbial populations during storage of full-fat Cheddar cheese
Journal of Dairy Science
Low fat cheese technology
International Dairy Journal
An investigation of the autolytic properties of three lactococcal strains during cheese ripening
International Dairy Journal
Tolerance to high osmolality of Lactococcus lactis subsp. lactis and cremoris is related to the activity of a betaine transport system
FEMS Microbiology Letters
Starter cultures: General aspects
Fate of Lactococcus lactis starter cultures during late ripening in cheese models
Food Microbiology
Starter cultures employed in cheese-making
Comparative transcriptome analysis of Lactococcus lactis subsp. cremoris strains under conditions simulating Cheddar cheese manufacture
International Journal of Food Microbiology
Proteolytic enzymes of dairy starter cultures
FEMS Microbiology Reviews
Overexpression of peptidases in Lactococcus and evaluation of their release from leaky cells
Journal of Dairy Science
Factors which may influence the determination of autolysis of starter bacteria during cheddar cheese ripening
International Dairy Journal
Effect of varying the salt and fat content in cheddar cheese on aspects of the performance of a commercial starter culture preparation during ripening
International Journal of Food Microbiology
Purification and characterization of a post-proline dipeptidyl aminopeptidase from Streptococcus cremoris AM2
Journal of Dairy Research
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