Characterizing the sarcoplasmic proteome of aged pork chops classified by purge loss

Abstract

Unpredictable variation in quality, including fresh pork water-holding capacity, remains challenging to pork processors and customers. Defining the diverse factors that influence fresh pork water-holding capacity is necessary to make progress in refining pork quality prediction methods. The objective was to utilize liquid chromatography and mass spectrometry coupled with tandem mass tag (TMT) multiplexing to evaluate the sarcoplasmic proteome of aged pork loins classified by purge loss. Fresh commercial pork loins were collected, aged 12 or 14 d postmortem, and pork quality and sensory attributes were evaluated. Chops were classified into Low (n = 27, average purge = 0.33%), Intermediate (n = 27, average purge = 0.72%), or High (n = 27, average purge = 1.19%) chop purge groups. Proteins soluble in a low-ionic strength buffer were extracted, digested with trypsin, labeled with 11-plex isobaric TMT reagents, and detected using a Q-Exactive Mass Spectrometer. Between the Low and High purge groups, 40 proteins were differentially (P < 0.05) abundant. The Low purge group had a greater abundance of proteins classified as structural and contractile, sarcoplasmic reticulum and calcium regulating, chaperone, and citric acid cycle enzymes than the High purge group. The presence of myofibrillar proteins in the aged sarcoplasmic proteome is likely due to postmortem degradation. These observations support our hypothesis that pork chops with low purge have a greater abundance of structural proteins in the soluble protein fraction. Together, these and other proteins in the aged sarcoplasmic proteome may be biomarkers of pork water-holding capacity. Additional research should establish the utility of these proteins as biomarkers early postmortem and over subsequent aging periods.

Distinct myofibrillar sub-proteomic profiles are associated with the instrumental texture of aged pork loin

“…The loins were vacuum packaged, transported on ice to Iowa State University, and aged for 12 or 14 d postmortem at 4 °C, where aging time varied to avoid freezing samples before sensory and quality analysis ­( Carlson et al, 2017b ). Fresh pork loin quality measurements, a trained sensory panel, and moisture and lipid proximate data were collected and analyzed as described by Johnson et al (2023) . The range and standard deviation of the quality and sensory measurements for the initial population of pork loins ( N = 120) are reported in Supplementary Table S1 .…”

“…Samples were vortexed, heated on a dry heat block for 15 min at ~50 °C, and stored at −80 °C. Confirmation of equal protein concentrations between samples was evaluated using 15% SDS–PAGE with a 5% stacking gel with 10 lanes, as described by Johnson et al (2023) .…”

“…The prepared myofibrillar extracts from each aged pork chop grouped by instrumental star probe ( n = 100) were submitted to the Iowa State Protein Facility for tandem mass tag (TMT) analysis, where the peptide preparation, chromatographic separation, and ion detection specifications were described previously ( Johnson et al, 2023 ). Briefly, 5 µg from each ­sample was pooled, reduced, alkylated, and digested with trypsin according to the manufacturer’s directions to serve as the Master Control sample.…”

“…Previous studies have utilized 1-dimensional sodium dodecyl sulfate-polyacrylamide gel (SDS-PAGE) or 2-dimensional difference in gel electrophoresis methods coupled with mass spectrometry to identify and quantify specific proteins related to pork quality attributes ( Hwang et al, 2005 ; Carlson et al, 2017a ; López-Pedrouso et al, 2020 ; Schulte et al, 2020 ; Zuber et al, 2021 ). Gel-free methods utilizing tryptic digestion and liquid chromatography–tandem mass spectrometry (LC–MS/MS) analysis with isobaric tags or label-free techniques have recently been applied to beef ( Schulte et al, 2023 ) and pork samples ( Huang et al, 2018 ; Liu et al, 2021 , 2022 ; Zequan et al, 2021 ; Johnson et al, 2023 ). Few of these studies have aimed to specifically evaluate the extent to which differences within the myofibrillar sub-proteome are associated with meat quality.…”

Extended Storage of Beef Steaks Using Thermoforming Vacuum Packaging

“…Water, as one of the primary components of meat, can be greatly altered by refrigerated storage temperatures, packaging methods, and storage duration [9]. Moisture losses occurring throughout the many phases of meat logistics from farm to consumer have been linked to negative changes in cooking yields, organoleptic properties, and even objective tenderness measurements [10].…”