Browsing by Subject "Maturation"

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Effect of storage temperature on volatile marker compounds in cured loins fermented with Staphylococcus carnosus by brine injection
(2020) Bosse, Ramona; Wirth, Melanie; Weiss, Jochen; Gibis, Monika
In this study, the influence of low (5 °C), intermediate (15 °C) and high (25 °C) storage temperatures on the profile of volatile compounds of North European cured loins fermented with Staphylococcus carnosus strains was investigated. In this context, proteolytic activity, bacterial growth, key volatile compounds and sensory attributes were studied. In conclusion, storage temperature significantly affected the volatile marker compounds. A multiple regression indicated significant effects of seven volatile compounds (acetophenone, benzaldehyde, butanone, 3-methylbutanal, 1-octen-3-ol, nonanal and pentanone) on the overall odor (R2 = 95.9%) and overall flavor (R2 = 81.1%). The sum of the marker volatiles aldehydes, ketones and alcohol increased with rising temperatures and the highest amounts of the odor active 3-methylbutanal up to 155 and 166 ng/g meat were detected in high temperature-stored loins. Moreover, the addition of S. carnosus strain LTH 3838 showed maximum effect at 5 °C-storage temperature in comparison to the control.
A novel, robust peptidyl-lys metalloendopeptidase from Trametes coccinea recombinantly expressed in Komagataella phaffii
(2024) Ahmed, Uzair; Stadelmann, Tobias; Heid, Daniel; Würtz, Berit; Pfannstiel, Jens; Ochsenreither, Katrin; Eisele, Thomas
A novel peptidyl-lys metalloendopeptidase ( Tc -LysN) from Tramates coccinea was recombinantly expressed in Komagataella phaffii using the native pro-protein sequence. The peptidase was secreted into the culture broth as zymogen (~38 kDa) and mature enzyme (~19.8 kDa) simultaneously. The mature Tc -LysN was purified to homogeneity with a single step anion-exchange chromatography at pH 7.2. N-terminal sequencing using TMTpro Zero and mass spectrometry of the mature Tc- LysN indicated that the pro-peptide was cleaved between the amino acid positions 184 and 185 at the Kex2 cleavage site present in the native pro-protein sequence. The pH optimum of Tc -LysN was determined to be 5.0 while it maintained ≥60% activity between pH values 4.5—7.5 and ≥30% activity between pH values 8.5—10.0, indicating its broad applicability. The temperature maximum of Tc -LysN was determined to be 60 °C. After 18 h of incubation at 80 °C, Tc -LysN still retained ~20% activity. Organic solvents such as methanol and acetonitrile, at concentrations as high as 40% (v/v), were found to enhance Tc -LysN’s activity up to ~100% and ~50%, respectively. Tc -LysN’s thermostability, ability to withstand up to 8 M urea, tolerance to high concentrations of organic solvents, and an acidic pH optimum make it a viable candidate to be employed in proteomics workflows in which alkaline conditions might pose a challenge. The nano-LC-MS/MS analysis revealed bovine serum albumin (BSA)’s sequence coverage of 84% using Tc -LysN which was comparable to the sequence coverage of 90% by trypsin peptides. Key points • A novel LysN from Trametes coccinea (Tc-LysN) was expressed in Komagataella phaffii and purified to homogeneity • Tc-LysN is thermostable, applicable over a broad pH range, and tolerates high concentrations of denaturants • Tc-LysN was successfully applied for protein digestion and mass spectrometry fingerprinting
Variations in the metabolome of unaged and aged beef from black-and-white cows and heifers by 1H NMR spectroscopy
(2023) Bischof, Greta; Januschewski, Edwin; Witte, Franziska; Terjung, Nino; Heinz, Volker; Juadjur, Andreas; Gibis, Monika
(1) Background: The selection of raw material and the postmortem processing of beef influence its quality, such as taste. In this study, the metabolome of beef from cows and heifers is examined for differences during aging. (2) Methods: Thirty strip loins from eight heifers and seven cows (breed code: 01–SBT) were cut into ten pieces and aged for 0, 7, 14, 21 and 28 days. Samples from the left strip loins were wet-aged in vacuum, while samples from right strip loins were dry-aged at 2 °C and 75% relative humidity. The beef samples were extracted with methanol–chloroform–water, and the polar fraction was used for 1H NMR analysis. (3) Results: The PCA and OPLS-DA showed that the metabolome of cows and heifers varied. Eight metabolites revealed significant differences (p < 0.05) in the samples from cows and heifers. The aging time and aging type of beef also affected the metabolome. Twenty-eight and 12 metabolites differed significantly (p < 0.05) with aging time and aging type, respectively. (4) Conclusions: The variations between cows and heifers and aging time affect the metabolome of beef. By comparison, the influence of aging type is present but less pronounced.