Shelf-life extension of minimally processed carrots by gaseous chlorine dioxide
V.M. Gómez-López, F. Devlieghere, P. Ragaert and J. Debevere
International Journal of Food Microbiology, Volume 116, Issue 2, 10 May 2007, Pages 221-227
2007
บทคัดย่อ
Chlorine dioxide (ClO2) gas is a strong oxidizing and sanitizing agent that has a broad and high biocidal effectiveness and big penetration ability; its efficacy to prolong the shelf-life of a minimally processed (MP) vegetable, grated carrots (Daucus carota L.), was tested in this study. Carrots were sorted, their ends removed, hand peeled, cut, washed, spin dried and separated in 2 portions, one to be treated with ClO2 gas and the other to remain untreated for comparisons. MP carrots were decontaminated in a cabinet at 91% relative humidity and 28 °C for up to 6 min, including 30 s of ClO2 injection to the cabinet, then stored under equilibrium modified atmosphere (4.5% O2, 8.9% CO2, 86.6% N2) at 7 °C for shelf-life studies. ClO2 concentration in the cabinet rose to 1.33 mg/l after 30 s of treatment, and then fell to nil before 6 min. The shelf-life study included: O2 and CO2 headspace concentrations, microbiological quality (mesophilic aerobic bacteria, psychrotrophs, lactic acid bacteria, and yeasts), sensory quality (odour, flavour, texture, overall visual quality, and white blushing), and pH. ClO2 did not affect respiration rate of MP carrots significantly (α≤ 0.05), and lowered the pH significantly (α≤ 0.05). The applied packaging configuration kept O2 headspace concentrations in treated samples in equilibrium and prevented CO2 accumulation. After ClO2 treatment, the decontamination levels (log CFU/g) achieved were 1.88, 1.71, 2.60, and 0.66 for mesophilic aerobic bacteria, psychrotrophs, and yeasts respectively. The initial sensory quality of MP carrots was not impaired significantly (α≤ 0.05). A lag phase of at least 2 days was observed for mesophilic aerobic bacteria, psychrotrophs, and lactic acid bacteria in treated samples, while mesophilic aerobic bacteria and psychrotrophs increased parallelly. Odour was the only important attribute in sensory deterioration, but it reached an unacceptable score when samples were already rejected from the microbiological point of view. The shelf-life extension was limited to one day due to the restricted effect of the ClO2 treatment on yeast counts. Nevertheless, ClO2 seems to be a promising alternative to prolong the shelf-life of grated carrots.