Characterization of Quality Properties in Spoiled Mianning Ham

Abstract

Deep spoilage is a cyclical and costly problem for the meat industry. Mianning ham is a famous dry-cured meat product in Sichuan, China. The aim of this work was to investigate the physicochemical characteristics, sources of odor, and associated microorganisms that cause spoilage of Mianning ham. High-throughput sequencing and solid-phase microextraction–gas-chromatography (SPME-GC-MS) techniques were used to characterize the physicochemical properties, microbial community structure, and volatile compounds of spoiled Mianning ham and to compare it with normal Mianning ham. The results showed that spoiled ham typically had higher moisture content, water activity (aw), and pH, and lower salt content. The dominant bacterial phylum detected in deeply spoiled ham was Firmicutes (95.4%). The dominant bacterial genus was Clostridium_sensu_stricto_2 (92.01%), the dominant fungal phylum was Ascomycota (98.48%), and the dominant fungal genus was Aspergillus (84.27%). A total of 57 volatile flavor substances were detected in deeply spoiled ham, including 11 aldehydes, 2 ketones, 6 alcohols, 10 esters, 20 hydrocarbons, 6 acids, and 2 other compounds. Hexanal (279.607 ± 127.265 μg/kg) was the most abundant in deeply spoiled ham, followed by Butanoic acid (266.885 ± 55.439 μg/kg) and Nonanal (165.079 ± 63.923 μg/kg). Clostridium_sensu_stricto_2 promoted the formation of five main flavor compounds, Heptanal, (E)-2-Octenal, 2-Nonanone, Hexanal, and Nonanal, in deeply spoiled ham by correlation analysis of microbial and volatile flavor substances.

Insight into the Relationship between the Causes of Off-Odour and Microorganism Communities in Xuanwei Ham

“…a w is the state in which water exists in the system, representing the degree to which it is bound (or degree of freedom) [ 15 ]. The higher the a w , the lower the degree of binding [ 15 ].…”

“…a w is the state in which water exists in the system, representing the degree to which it is bound (or degree of freedom) [ 15 ]. The higher the a w , the lower the degree of binding [ 15 ]. In this study, the a w of spoiled hams ranged from 0.87 to 0.88, while that of normal hams ranged from 0.74 to 0.75.…”

“…The moisture content was determined according to the method of Marusic et al [ 31 ]. The a w was measured using a LabMaster water activity metre (LabMaster, Novasina, Switzerland) according to the method of Zhu et al [ 15 ]. The NaCl content was determined using atomic absorption spectrometry (AAS, Agilent Technologies, Santa Clara, CA, USA) according to the method of Gamela et al [ 32 ].…”

“…A variety of microorganisms are present both inside and on the surface of the dry-cured ham, which is considered to play a crucial role in flavour development by facilitating proteolytic reactions and lipid oxidation during the product processing procedure [ 14 ]. Under specific circumstances, certain types of microorganisms undergo rapid proliferation inside or on the surface of the ham, resulting in the deterioration of the ham [ 15 ]. The presence of an unpleasant odour, along with accompanying deviations in colour and texture, renders the ham in question unsuitable for consumption [ 16 ].…”

“…The corrosion of the hams is related to the proteolytic and lipolytic reactions in the ham, especially in which the odour generated is closely associated with the metabolic action of the microorganisms [ 10 ]. Several studies have investigated the compositions and dynamics of microbial communities, as well as their impact on the production of volatile compounds in dry-cured ham [ 10 , 15 , 24 , 25 ]. However, there is still a lack of comprehensive knowledge on the microbial diversity and flavour development of Xuanwei ham, especially the relationship between abnormal microbial growth and off-odour formation.…”