Influence of Hurdle Applications on the Storage Stability of Dambu-nama

Abstract

The microbiological, physico-chemical, sensory and storage characteristics of dambu-nama (DN) as influenced by addition of citric acid, salt and sugar as hurdles were investigated. Preliminary sensory evaluation suggested that at citric acid level above 0.3%, sugar and salt levels above 2% each, the products were either too harsh or sweet for acceptance. Four products comprising DN with 0.1% citric acid + 2% salt and 2% sugar (DNC0.1), DN+ 0.2% citric + 2% salt + 2% sugar (DNC0.2), DN + 0.3% citric acid + 2% salt + 2% sugar (DNC0.3) and a control DN without citric acid , salt or sugar (DNC0) were produced and subjected to microbiological, sensory and storage analyses. Treatment of dambu-nama with the hurdles resulted in significant (p< 0.05) decrease in total plate and mould counts. Thiobarbituric acid, tyrosine and total plate counts varied very little with no definite trend, there by ruling out their use as possible indices of quality. The pH of dambu-nama exhibited a slow but definite decline with storage. The decrease in pH was best described by first order reaction kinetics (r2 ≥ 0.987) and adequately by the Arrhenius activated energy complex theory (r2 ≥ 0.991) with activation energies (kJ/mol) of 32.6 (DNC0), 27.6 (DNC0.1), 23.1 (DNC0.2) and 54.5 (DNC0.3), respectively. Treatment with the hurdles increased shelf-life of dambu-nama by a factor of 2.3 to 8.4 with shelf-life (wks) of 7.7 to 4.3 (DNC0), 17.8 to 10.3 (DNC0.1), 33.3 to 21.0 (DNC0.2) and 64.9 to 27.9 (DNC0.3), respectively for storage at 20 to 35oC. The objective of this study thus was to investigate quality changes in dambu-nama during normal and accelerated storage as influenced by the hurdles with the purpose of shelf-lives predictions.