Abstract
Late blowing defect (LBD) is an important spoilage issue in semi-hard cheese, with the outgrowth of Clostridium tyrobutyricum spores during cheese aging considered to be the primary cause. Although previous studies have explored the microbial and physicochemical factors influencing the defect, a risk assessment tool that allows for improved and rational management of LBD is lacking. The purpose of this study was to develop a predictive model to estimate the probability of LBD in Gouda cheese and evaluate different intervention strategies. The spore concentration distribution of butyric acid bacteria (BAB) in bulk tank milk was obtained from 8 dairy farms over 12 mo. The concentration of C. tyrobutyricum from raw milk to the end of aging was simulated based on Gouda brined for 2 d in saturated brine at 8°C and aged at 13°C. Predicted C. tyrobutyricum concentrations during aging and estimated concentration thresholds in cheese at onset of LBD were used to predict product loss due to LBD during a simulated 1-yr production. With the estimated concentration thresholds in cheese ranging from 4.36 to 4.46 log most probable number (MPN)/kg of cheese, the model predicted that 9.2% (±1.7%) of Gouda cheese showed LBD by d 60; cheeses predicted to show LBD at d 60 showed a mean pH of 5.39 and were produced with raw milk with a mean BAB spore count of 143 MPN/L. By d 90, 36.1% (±3.4%) of cheeses were predicted to show LBD, indicating that LBD typically manifests between d 60 and 90, which is consistent with observations from the literature and the cheese industry. Sensitivity analysis indicated that C. tyrobutyricum maximum growth rate as well as concentration threshold in cheese at onset of LBD are the most important variables, identifying key data needs for development of more accurate models. The implementation of microfiltration or bactofugation of raw milk (assumed to show 98% efficiency of spore removal) in our model prevented occurrence of LBD during the first 60 d of aging. Overall, our findings provide a framework for predicting the occurrence of LBD in Gouda as well as other cheeses and illustrate the value of developing digital tools for managing dairy product quality.
Highlights
Late blowing defect (LBD) is a major spoilage issue in semi-hard cheeses and is characterized by formation of cracks and slits in the cheese matrix as well as unpleasant rancid flavor due to unwanted butyric acid fermentation that produces gas and butyric acid
For these reasons and due to the fact that it is more salt tolerant than other butyric acid bacteria (BAB), C. tyrobutyricum has been presented as the primary cause of semi-hard cheese LBD in multiple studies and book chapters (Klijn et al, 1995; Le Bourhis et al, 2007; Garde et al, 2013; D’Amico, 2014; Düsterhöft et al, 2017)
The model developed here consists of 3 modules, including (i) a module that simulates transfer of spores from raw milk to cheese before the aging stage, (ii) a module that predicts the growth of C. tyrobutyricum during cheese aging, and (iii) a module that predicts the occurrence of LBD at a given aging time based on C. tyrobutyricum concentration in cheese (Figure 1)
Summary
Late blowing defect (LBD) is a major spoilage issue in semi-hard cheeses and is characterized by formation of cracks and slits in the cheese matrix as well as unpleasant rancid flavor due to unwanted butyric acid fermentation that produces gas and butyric acid. An anaerobic gram-positive spore-former, Clostridium tyrobutyricum is capable of butyric acid fermentation and is able to grow and produce gas at typical aging temperatures and salt concentrations used in production of cheeses such as Gouda and Emmental (Su and Ingham, 2000). These brined cheeses are susceptible to LBD because the salt can take time to migrate to the interior of cheese matrix and is unable to limit the growth of C. tyrobutyricum at initial phases of aging. These factors include cheese brining and aging conditions (Su and Ingham, 2000), the use of nisin-producing lactic acid bacteria (Toyoda and Nakajima, 1995; Rilla et al, 2003; Ávila et al, 2020), and
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