Conductometric titration to determine total volatile basic nitrogen (TVB-N) for post-mortem interval (PMI)

Abstract

Precise measurement of cadaver decomposition rate is the basis to accurate post-mortem interval (PMI) estimation. There are many approaches explored in recent years, however, it is still unsolved completely. Total volatile basic nitrogen (TVB-N), which is an important index to predict meat freshness and shelf life in food science, could serve as an indicator for measuring PMI associated decomposition rate of cadavers. The aim of this work was to establish a practical method to determine TVB-N in cadaver soft tissues (mainly skeletal muscle) for measuring decomposition rate. Determination of TVB-N in the simulation and animal experiments was conducted by steam distillation and conductometric titration using Kjeldahl distillation unit and conductivity meter. In simulation, standard concentrations of ammonium were used as TVB analogies, TVB-N contents were determined and the recovery rates of nitrogen were calculated. In animal experiment, TVB-N in skeletal muscle of forty-two rats was determined at different PMIs for 312 h at 24 °C ± 1 °C. The relationship between PMI and TVB-N was investigated also. The method showed high precision with 99%–100% recovery rates. TVB-N in skeletal muscle changed significantly with PMI especially after 24 h, and the data fit well to y = 3.35 E−5x3-2.17 E−2x2+6.13x-85.82 (adj. R2 = 0.985). ECi (initial electrical conductivity in the samples just before titration) had positive linear relationship to final measured TVB-N values, y = 1.98x+16.16 (adj. R2 = 0.985). The overall results demonstrated that the method is accurate, rapid and flexible, which could be expected as a basic technique for measuring decomposition rate in later PMI-estimation researches. Further studies are needed to validate our findings.