Application of exopolysaccharide-forming lactic acid bacteria in cooked ham model systems

Abstract

The meat industry often applies hydrocolloids (not label-free) to improve quality attributes of meat products including reconstructed cooked ham. A new approach to improve product quality could be the usage of in-situ Exopolysaccharide (EPS)- forming lactic acid bacteria (LAB) provided that these strains are able to produce EPS in meat matrices under typical processing conditions (here: cooked ham). Two homopolysaccharide- (L. curvatus TMW 1.624 and L. sakei TMW 1.411; 10⁶CFUmL) and heteropolysaccharide-forming LABs (L. plantarum TMW 1.1478 and TMW 1.25; 10⁶CFUmL) were hence examined for EPS formation in a cooked ham model system consisting of minced pork topside (<2% fat) and 16.67% brine containing either 0.5% sucrose or dextrose. Samples were stored for 48 h at either 2 °C to simulate typical tumbling conditions, or at 15 °C to examine in-situ EPS production under reduced stress conditions. Microbial growth behavior and pH development (48 h) were monitored and EPS qualitatively as well as semi-quantitatively analyzed using both confocal laser scanning microscopy and MATLAB enabling a better comparison of the investigated strains. All LAB were able to tolerate the suboptimal growth conditions in the cooked ham model systems (2 °C, 1.92% nitrite curing salt) and were found to already produce EPS within 10 h of storage at 2° and 15 °C. EPS amounts detected after 24 h of incubation were significantly (p < 0.05) higher than those determined after sample preparation. EPS were found to be predominately located at the outer edge of meat proteins. All investigated strains seem to be promising for prospective studies in cooked ham.

Keywords: CLSM; Cooked ham; Exopolysaccharides; Image analysis; Lactobacillus ssp.; Qualitative EPS analytics.