Characterization of tyramine producing Lentilactobacillus otakiensis isolated from aged Cheddar cheese and strategies of control

Characterization of nutty flavor in cheddar cheese.

To determine the taste components of Cheddar cheese, we fractionated one mild Cheddar cheese and one aged Cheddar cheese by water extraction, freeze‐drying and gel filtration. Salty, sour and umami were the three predominant tastes present in the fractions. Neither trigeminal sensations nor astringency was perceived. We used response surface methodology to reconstruct a mild Cheddar cheese taste and an aged Cheddar cheese taste in water. Less salt and less acid were needed to simulate the taste of mild Cheddar cheese, compared with aged Cheddar cheese. Our optimized water solutions (containing sodium chloride, lactic acid and monosodium glutamate) were as similar to the real cheese samples as were the water extracts of the standard cheeses. However, neither our optimized solutions nor the water extracts matched the taste of the actual cheeses.

Quantitation of Growth of Mold on Cheese

A Gram-stain positive, rod-shaped, non-spore-forming strain (WDC04T), which may be associated with late gas production in cheese, was isolated from aged Cheddar cheese following incubation on MRS agar (pH 5.2) at 6 °C for 35 days. Strain WDC04T had 97 % 16S rRNA gene sequence similarity with Lactobacillus hokkaidonensis DSM 26202T, Lactobacillus oligofermentans 533, 'Lactobacillus danicus' 9M3, Lactobacillus suebicus CCUG 32233T and Lactobacillus vaccinostercus DSM 20634T. API 50 CH carbohydrate fermentation panels indicated strain WDC04T could only utilize one of the 50 substrates tested, ribose, although it does slowly utilize galactose. In the API ZYM system, strain WDC04T was positive for leucine arylamidase, valine arylamidase, cysteine arylamidase (weakly), naphthol-AS-BI-phosphohydrolase and β-galactosidase activities. Total genomic DNA was sequenced from strain WDC04T using a whole-genome shotgun strategy on a 454 GS Titanium pyrosequencer. The sequence was assembled into a 1.90 Mbp draft genome consisting of 105 contigs with preliminary genome annotation performed using the RAST algorithm (rast.nmpdr.org). Genome analysis confirmed the pentose phosphate pathway for ribose metabolism as well as galactose, N-acetylglucosamine, and glycerol fermentation pathways. Genomic analysis places strain WDC04T in the obligately heterofermentative group of lactobacilli and metabolic results confirm this conclusion. The result of genome sequencing, along with 16S rRNA gene sequence analysis, indicates WDC04T represents a novel species of the genus Lactobacillus, for which the name Lactobacillus wasatchensis sp. nov. is proposed. The type strain is WDC04T ( = DSM 29958T = LMG 28678T).

Recent flavor chemistry studies have identified flavor compounds at different concentrations in full- and low-fat Cheddar cheeses. The specific flavor contributions of these compounds in full- and low-fat cheese matrices have not been established. The purpose of this study was to evaluate the sensory response of Cheddar flavor compounds in model full-fat and 75% reduced-fat cheeses. Odor activity values (OAVs) for each compound in full- and reduced-fat cheeses were calculated. Each compound was then added to model cheeses created from 3-week-old full- and reduced-fat Cheddar cheeses. A trained sensory panel (n = 8) evaluated the sensory properties of the cheese models. The final combination of compounds was incorporated into reduced-fat cheese models, and consumers (n = 85) evaluated perceived-aged Cheddar cheese aroma. Based on OAVs and perception of the individual compounds in cheese models, 12 key flavor compounds were identified. Target ideal concentrations of specific cheese flavor compounds in 75% reduced-fat cheese were determined. According to consumers, the perceived aged Cheddar cheese aroma intensity of reduced-fat model cheese with these added compounds was not different (P > 0.05) from the perceived Cheddar cheese aroma intensity of commercial aged full-fat Cheddar cheeses. PRACTICAL APPLICATION The market for reduced-fat Cheddar cheese is increasing as consumers become more health conscious. The structure and biochemistry of reduced-fat Cheddar cheeses are altered, and flavor and texture remain a challenge. This study established the role of 23 volatile compounds using descriptive analysis of cheese model systems. The impact of key compound concentration differences and how these differences affect sensory perception of cheese flavor in full- and 75% reduced-fat Cheddar cheeses were determined. These results provide guidance for mimicking aged Cheddar cheese flavor in reduced-fat cheese.

There is tremendous variability in flavor profiles of sharp or aged U.S. cheddar cheese due to varied practices among commercial facilities and the lack of legal definitions for these terms. This study explored U.S. consumer perception and liking of commercial sharp or aged cheddar cheese profiles. Flavor profiles of 29 representative sharp cheddar cheeses were documented by descriptive sensory analysis with a trained panel. A total of 9 representative cheddar cheeses were selected and evaluated by consumers in 3 regional locations: east coast (Raleigh, N.C.; n = 150), midwest (Champaign, Ill.; n = 75), and west coast (Pullman, Wash.; n = 100). Consumers assessed the cheeses for overall liking and other consumer liking attributes. External preference mapping revealed 5 distinct consumer segments. The segment membership distribution between east coast and midwest consumers was similar while the west coast distribution was distinct (P < 0.05). A larger proportion of west coast consumers were present in segment 3, which consisted of consumers with specific likes for cheeses characterized by intense flavors of free fatty acid, brothy, and nutty flavors and salty and sour tastes. Consumer preferences in other segments differed from segment 3 due to their liking of at least 1 sensory attribute generally associated with young or mild cheddar cheese flavor. Key drivers of liking for these segments included whey flavor for segments 1 and 4 and milkfat flavor for segment 5. Segment 2 consumers liked most of the cheeses tested except those with dominant whey flavor. A sharp or aged cheddar cheese label means different things to different consumers and liking profiles are not defined by consumer location.

Effect of proteolysis during Cheddar cheese aging on the detection of milk protein residues by ELISA

The compounds responsible for the bitter taste of aged "sharp" Cheddar cheese were characterized. Sensory-guided fractionation techniques using gel permeation chromatography and multi-dimension semi-preparative reversed-phase high-performance liquid chromatography revealed the presence of multiple bitter compounds. The compounds with the highest perceived bitterness intensity were identified by tandem mass spectrometry de novo peptide sequencing as GPVRGPFPIIV, YQEPVLGPVRGPFPI, MPFPKYPVEP, MAPKHKEMPFPKYPVEPF, and APHGKEMPFPKYPVEPF; all originated from β-casein. Subsequent quantitative liquid chromatography-tandem mass spectrometry analysis reported that the concentrations of GPVRGPFPIIV, YQEPVLGPVRGPFPI, and MPFPKYPVEP increased during maturation by 28.7-, 3.1-, and 1.8-fold, respectively. When directly compared to young "mild" Cheddar, APHGKEMPFPKYPVEPF was reported only in the sharp Cheddar cheese, whereas the concentration of MAPKHKEMPFPKYPVEPF did not change. Further taste re-engineering sensory experiments confirmed the importance of the identified peptides to the bitterness of sharp Cheddar. The bitter intensity of the aged "sharp" Cheddar model (mild Cheddar with equivalent concentrations of the five bitter peptides in the sharp sample) was rated as not significantly different from the authentic sharp Cheddar cheese. Among the five peptides, GPVRGPFPIIV was reported to be the main contributor to the bitterness intensity of sharp Cheddar. Furthermore, a difference from control sensory test also confirmed the significance of the bitter taste to the overall perception of aged Cheddar flavor. The sharp Cheddar model was reported to be significantly more similar to aged "sharp" Cheddar in comparison to the young "mild" Cheddar cheese sample.

During cheese ripening, the proteins in the cheese are broken down, and various functional peptides are produced. This research aimed to investigate the changes in peptides and their physiological activities during the long-term maturation of Cheddar cheese. Young (YC), medium (MC), and 3-year-aged extra-sharp (EC) Cheddar cheeses were extracted with water, and bioactive peptides were identified using ultra performance liquid chromatography-high resolution mass spectrometer. Peptides reported to have antioxidant, angiotensin-converting enzyme (ACE)-inhibitory, and anti-inflammatory effects were identified and evaluated in the extracts. MC and EC showed stronger antioxidant activity than YC. The 2,2'-azino-bis-(3-ethylbenzothiazoline-6-sulfonic) acid inhibition rates of MC and EC were similar, but EC exhibited a higher 2,2-diphenyl-1-picrylhydrazyl inhibition rate. The antihypertensive effect was found to increase owing to the appearance of peptides with ACE-inhibitory activity in MC and EC. Quantitative real time polymerase chain reaction and immunoblot were run to evaluate the anti-inflammatory effects. YC did not show anti-inflammatory activity, but MC and EC were shown to effectively inhibit inflammatory mRNA expression. The immunoblot results showed that EC did not inhibit IκBα phosphorylation, but had an inhibitory effect at the mRNA expression level. Overall, the peptides contained in aged Cheddar cheese were shown to have excellent antioxidant, anti-inflammatory, and antihypertensive activities, and long-term ripening appeared to have a positive effect on these activities. This is presumed to have affected not only the already identified peptides but also unknown peptides; therefore, it is expected that the discovery of bioactive peptides will be possible through additional research.

Reduced-fat cheddar cheese manufactured using a novel fat removal process.

Angiotensin-I-converting enzyme-inhibitory peptides in commercial Wisconsin Cheddar cheeses of different ages

Hot Topic: Black Spot Defect in Cheddar Cheese Linked to Intramammary Teat Sealant

Impact of Low Concentration Factor Microfiltration on the Composition and Aging of Cheddar Cheese

Control of Heterofermentative Bacteria During Cheddar Cheese Maturation by Homofermentative Lactobacillus Starters

From an enrichment culture of white-crystal deposits from aged Cheddar cheese, an atypical Lactobacillus strain was characterized. The new isolate is facultatively heterofermentative, has a G + C content of 40 mol%, and produces D and L isomers of lactic acid. The strain had a limited ability to ferment carbohydrates. It utilized fructose, galactose, glucose, lactose, maltose, mannose, and ribose but was negative for esculin, gluconate, citrate, and several other carbon sources. The isolate also had low DNA-DNA homologies with strains of Lactobacillus casei and Lactobacillus plantarum. Cheese prepared with milk containing the isolate developed white crystals during curing. Formation of copious D-lactate from unknown substrates during curing probably caused the white-crystal deposits. The strain has been deposited in the American Type Culture Collection (ATCC 49178).