Abstract:
This research was aimed to study the effects of modified atmosphere packaging (MAP) on qualities
and shelf life of ready-to-cook cockles. The study was divided into 3 parts. Firstly, the shelf life of
raw cockles were studied. Secondly, the effects of blanching time (1-6? min) of ready-to-cook
cockles blanched at 100?C were investigated. Finally, the effects of modified atmospheres (20%
CO2 + 20% 02 + 60% N2, 40% CO2 + 20% 02 + 40% N2 and 60% CO2 + 20% 02 + 20% N2) on
qualities and shelf life of ready-to-cook cockles packed in nylon/PE bags and stored at 4?2 ?C were
determined.
In the first part, the results showed that pH value of cockles tended to decrease from 6.73?0.02 to
6.37?0.77 as the storage time increased whereas weight loss, TMA and TVB-N of cockles increased
from 0.96?0.11 to 1.33?0.53%, 6.73?0.03 to 12.24?0.11 mgllOO g of sample and 17.96?3.89 to
51.94?3.77 mgllOO g of sample, respectively. Total viable count of cockles were increased from
4.85?0.31 to 10.47?0.0I log cfu/g on 12 days of storage. Based on the standard of Medical Sciences
Department, the raw cockles were spoiled by microorganism and its shelf life was 6 days.
For the second part, the results showed that %yield and expressible moisture of cockles as well as
sensory scores (odor and color) decreased as the blanching time increased. Total viable count of
cockles were decreased from 4.94?0.06 to 2.13?0.07 log cfu/g. The sensorial results showed that
cockles blanched in boiled water for 3 min had the highest texture scores and overall acceptability
scores (p:S;0.05).
For the final part, the results showed that storage time had significant effect on microbiological
quality of all ready-to-cook samples (p:S;0.05). Total viable count of ready-to-cook cockles increased
from 2.57?0.03 to 8.95?0.04, 8.04?0.09, 7.97?0.05 and 9.20?0.05 log cfu/g at the end of
experimental period for the samples packed under 20% COz + 20% O, + 60% Nz' 40% COz + 20%
O, + 40% Nz, 60% C0z + 20% O, + 20% N, and air condition, respectively. Weight loss, TM.~ and
TVB-N of all treatments significantly increased as storage time progressed. In contrast, Aw, texture,
and sensory scores of the samples tended to decrease with increasing storage time. MAP conditions
had significant effects on qualities of ready-to-cook cockles. As the carbondioxide concentration in
the package increase weight loss, Aw and overall acceptability of ready-to-cook cockles increased
from 2.07?1.l0 to 6.71?1.29%, 0.982?0.00 to 0.984?0.00 and 3.15?1.01 to 3.66?0.78, respectively
whereas TMA and pH of ready- to-cook cockles decreased from 2.1 1?I.12 to 1.41?0.79 mg/lOO g of
sample and 7.19?0.1 0 to 6.93?0.06, respectively. Based on microbiological, chemical and sensorial
properties, the ready-to-cook cockles stored under 20% COz + 20% O, + 60% Nz, 40% COz + 20%
0z + 40% Nz, 60% COz + 20% O, + 20% N, and air condition could be kept at 4?2 DC for 12, IS, 21
and 4 days, respectively.
All the results revealed that the recommended practice for extending shelf life of ready-to-cook
cockles was blanching the cockles in boiling water (100 DC) for 3 min and then packing in nylon/PE
bags under modified atmospheric condition of 60% CO2 + 20% 02 + 20% N2. The products
aforementions could keep up their qualities for 21 days at 4?2 DC.