Abstract
Thermoduric bacteria are known to affect the quality of Cheddar cheese, with manifested defects including slits, weak body, and blowing. Thermoduric bacteria are likely to increase in numbers during cheese-making, as in-process conditions are conducive to proliferation. The present study was conducted to track thermoduric bacterial progression during an 18- to 20-h Cheddar cheese production run and during ripening when the pasteurizer was washed at midway through the production day. This study also correlated a broad range of chemical changes to the growth of thermoduric bacteria during ripening. Three independent cheese trials were performed at 3.5- ± 0.5-mo intervals. Samples were drawn in duplicates at 4 different times of the day: at the start of the run (vat 1), prior to a midday wash of the pasteurizer (vat 20), after the midday wash of the pasteurizer (vat 21), and at the end of the run (vat 42) for raw milk, pasteurized milk, and cheese. Cheeses were also tested during ripening for 6 mo. Results showed that raw milk total bacterial counts comprised 0.24% thermoduric mesophiles (TM) and 0.12% thermoduric thermophiles (TT). The thermoduric thermophilic bacterial counts increased by log10 1.23 during the pasteurizer run of 9 to 10 h, indicating a buildup of thermoduric thermophilic bacteria during the pasteurization process itself. Midday washing reduced thermophilic counts by log10 1.36, as evident by pre- and post-midday wash counts. However, a thermophilic buildup during post-midday wash was again noticed near the end of the 20-h run. We found that TT bacteria decreased in the first 60 d of ripening, whereas TM bacteria increased during the same period. However, TT bacteria increased later during 60 to 180 d of ripening. Bacillus licheniformis was the most frequently isolated bacteria in this study and was recovered at all production stages sampled during the cheese-making and ripening. We observed a significant increase in the level of orotic and uric acids in the vat made at the end of the day. No significant difference in the overall chemical composition, proteolysis, sugar, or other organic acids was observed in cheese made at the start versus the end of the production run.
Highlights
The cheese market is growing every year in the United States
The average total viable counts (TVC) in raw milk samples was log10 4.38 cfu/ mL, of which log10 1.76 were thermoduric mesophiles (TM) bacteria and log10 1.44 were thermoduric thermophiles (TT) bacteria, which translates to 0.24% TM and 0.11% TT, respectively
This finding is in agreement with previous work reported by Buehner et al (2014), who reported that raw milk in the Midwest region contains log10 1.85 cfu/ mL of TM and log10 0.91 cfu/mL of TT
Summary
Cheese production in the United States reached 0.5 billion kilograms in May 2018 and has increased by 1.4% since May 2017. Despite maintaining good sanitary conditions in cheese manufacturing plants, thermoduric bacteria are a constant matter of concern for cheese quality (Hull et al, 1992) and extended shelf-life, as the export of cheese has increased. The lengthy processing hours and increasing capacity (vat numbers and vat sizes) of cheese plants are 2 prominent factors that may lead to substantial financial losses if any spoilage occurs in the final product (Hull et al, 1992; Lauzon, 2018). Thermoduric bacteria, by definition (Frank and Yousef, 2004), can survive the pasteurization process (72°C/16 s). Several cheese defects related to flavor and texture, early and late blowing of cheese (Dasgupta and Hull, 1989; Klijn et al, 1995; Ortakci et al, 2015; Sutariya et al, 2020), soft-body (Hull et al, 1983), phenolic flavor, gray spot, and biogenic amines
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
