Safety control indices for plaa-som, a Thai fermented fish product.


Phikunthong Kopermsub and Sirinda Yunchalard *

This study was aimed to determine chemical and microbiological changes during plaa-som fermentation process. The results have been considered for use as safety control indices to obtain a higher quality and safer plaa-som. The fermentation process can be divided into an initiation stage (samples 1 to 3) and a maturation stage (samples 4 to 9) based on the changes obtained. At the initiation stage, pH remained stable at 6.3 and then rapidly declined during the maturation stage as from 6.3 to 4.5. Total acidity showed a continuous increasing trend from 0.12% (w/w) in sample 1 to 1.17% (w/w) in sample 9. Lactic and citric acids were detected as major acids during the initiation stage in a range of 0.22 - 0.29% (w/w). The main acids detected during the maturation stage, however, were lactic and acetic acids and these reached maximum levels at 2.82 and 0.16% (w/w) in samples 9 and 8, respectively. Substantial discrepancies between total viable counts (TVC) and lactic acid bacteria (LAB) counts were obtained during the initiation stage, particularly in sample1 where the TVC was 2.97 log CFU/g and LAB count was lower than 10 CFU/g. This indicated an existence of undesirable indigenous microorganisms other than LAB. At the maturation stage, the two counts concomitantly increased and no discrepancy was found. Maximum counts of TVC and LAB were 6.83 and 6.72 log CFU/g in samples 6 and 9, respectively. Good practices at particular steps and possible critical control points were noted and proposed for a more controllable plaa-som production process which will guide to a higher standard in both safety and quality consistency of the product. 

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