Changes in the Volatile Composition of Fresh Pork Sausage with Natural Antioxidants During Long-Term Frozen Storage

Pre-rigor meat was formulated into fresh pork sausages with a combination of synthetic antioxidants (butyl-ated hydroxyanisole, butylated hydroxytoluene, and propyl gallate) or the same synthetic antioxidants in combination with rosemary (R, 1500, 2000, 2500 mg/kg) and green tea (G, 100, 200, 300 mg/kg). Sausages were stored frozen (-20°C) for 15, 90, or 180 d followed by refrigerated storage (3 ± 1°C). The volatile compounds from these sausages were identified using solid phase microextraction (SPME), gas chromatography coupled with a mass selective detector (GC-MSD), and OSME-gas chromatography-olfactometry (GCO-OSME). Fifty-five aroma compounds were identified from the headspace of pork sausage where spice-derived volatiles such as terpenes (α-pinene, α-thujene) and terpenoids (isopulegol, 1,8-cineole) were the most abundant compounds in the headspace of the fresh product (0 d). Aldehydes (hep-tanal, 2-heptenal, (E,E)-2,4-decadienal) and alcohols (1-octen-3-ol, 1-penten-3-ol) characteristic of lipid degradation and microbial metabolites (methanethiol, 3-methylbutanoic acid, acetoin) were associated with more intense odorants as the product neared the end of shelf life at 14 d of refrigerated storage. Incorporation of R resulted in lower levels of hexanal (cut grass) and 1-octen-3-ol (mushroom) across all frozen storage periods. After 180 d of frozen storage, higher levels of G contained lower concentrations of ethanol (alcoholic), 3-methylbutanoic acid (sweaty), and 2-acetyl-1-pyrroline (pop-corn). As R and G concentration increased in the sausage, there were greater (P < 0.05) concentrations of terpenes and less (P < 0.05) acetic acid throughout refrigerated storage. Incorporation of R resulted in less (P < 0.05) 2,4-decadienal (oxidized ginger-nutmeg), and methanethiol (sulfur) following 90 d of freezing. After 180 d frozen storage, higher levels of G led to less (P < 0.05) 3-methyl-1-butanol and methyl isovalerate (spoiled fruit). Enhanced protection by natural plant extract combinations was observed, especially beyond 90 d of frozen storage where oxidation associated aroma-impact volatiles were reduced in sausages with higher rosemary and/or green tea extract concentrations.