Abstract
Nuodeng ham is known for its unique processing techniques and flavor. In the present study, proteolytic microorganisms from cured artisanal Nuodeng ham were investigated in order to identify and select potential starter cultures for its faster and safer fermentation. Eight isolates, accounting for 57% of proteolytic microorganisms, were found to be related to Kocuria rhizophila. Relevant properties of K. rhizophila as potential starter culture were evaluated in vitro for the first time. Intra-species diversities were found in phylogenetic and physiological properties of K. rhizophila isolates. Nevertheless, desirable attributes, such as halo-tolerance, nitrate reductase and protease activity, as well as the absence of antimicrobial resistance and amino acid decarboxylase activity, were observed in selected isolates. Moreover, genome analysis of isolates K24 and K45 confirmed their lack of typical genes for virulence, antimicrobial resistance and amino acid decarboxylase. K. rhizophila may thus represent a novel starter candidate of coagulase-negative cocci group and contribute to color and flavor development of fermented meats.
Highlights
Dry-cured ham is traditionally made by Bai ethnic people in Nuodeng village, Dali, Yunnan Province, thanks to local salt reserves and favorable climate
There is a need to identify technologically relevant bacteria from artisanal Nuodeng ham for the selection of starter cultures because autochthonous starters are better adapted to the specific habitat and can help maintain its organoleptic characteristics in a shorter ripening time (Casquete et al, 2011, 2012)
Since a high proportion of isolates (8/14 isolates) with high proteolytic activity were affiliated with K. rhizophila, the potential of K. rhizophila as eligible starter cultures for fermented meats was explored
Summary
Dry-cured ham is traditionally made by Bai ethnic people in Nuodeng village, Dali, Yunnan Province, thanks to local salt reserves and favorable climate. Coagulase-negative cocci (CNC) or Gram-positive catalasepositive cocci are important microbial group in meat fermentation They participate in color and flavor development of dry-cured meats through their enzymatic activities (Fonseca et al, 2013; Vermassen et al, 2016; Cruxen et al, 2017; Hu et al, 2018). Scannell et al (2004) selected a K. varians isolate with proteolytic activity from dry cure hams and used it in combination with Lactobacillus sakei to start a non-dried fermented ham product. Since a high proportion of isolates (8/14 isolates) with high proteolytic activity were affiliated with K. rhizophila, the potential of K. rhizophila as eligible starter cultures for fermented meats was explored To our knowledge, this is the first report on the technological and safety features of K. rhizophila for food application
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