English abstract
Oman is one of the developing countries rich in marine resources. Fish drying is
one of the traditional methods where the fishermen land their catch on the beaches for
drying traditionally under sun for several days. Many of the physicochemical and
microbiological changes occur during drying process. The traditional sun-drying
approach incurs major losses in the quantity and quality. Dried fish also suffer from
insects and sand contamination. The presence of microorganisms is another major
factor affecting the quality of dried fish. Therefore, this study aims to determine the
drying characteristics, establish a suitable single-layer drying model for anchovy,
determine the physical quality changes in anchovy under solar drying methods, and to
verify and compare the chemical and microbial contamination in solar dried anchovy
against the commercially available dried anchovy. One of the common types of
traditionally dried fish in Oman was selected and collected fresh namely; Anchovy.
About (20 kg) of anchovy were taken for experiments. Different analyses were
conducted in the samples before, during, and after drying. Drying processes were done
using three different methods which are open sun drying (OSD), solar greenhouse
tunnel dryer (GTD), and forced-convective solar dryer (FCD). The parameters analyzed
included three main analyses which are physical, chemical, and microbial analyses.
Results showed that the Henderson and Pabis model was greatly fitted with OSD
whereas Middili et al. model was fitted well with GTD and FCD. The drying rate was
higher in GTD compared to the two other methods. Moisture content, drying rate, and
moisture ratio were significantly affected by drying methods. GTD required less time
(6 hr) to dry anchovies compared to other drying methods (9 hr time). The highest
reduction in lightness is in GTD dried anchovies followed by FCD and OSD. The
drying methods and drying time statistically affect the Lightness (L) of dried anchovies
(p<0.05). The first-order kinetic model was fitted well with the lightness of dried
anchovies. No nitrosamines contamination was found in solar dried anchovies. The
water activity of solar-dried anchovies (0.3) was lower compared to the commercially
available anchovies (0.7). Experimentally dried anchovies were found to have lower
microbial count compared to the dried fish quality standards. The total viable count
(TVC) in fresh anchovy was 6.44 (log CFU/g) compared to the greenhouse tunnel dryer
(2.90 log CFU/g), open sun dryer (4.16 log CFU/g) and forced convective dryer (4.19
log CFU/g) anchovies. Water activity and moisture content did not affect total viable
count (TVC) significantly, but it affects total fungal count (TFC) (p<0.05). There was
a significant difference between the samples of three methods of drying and a fresh one
on the water activity, ash content, and fat content (p≤0.05). Overall, the study showed
that the greenhouse tunnel dryer (GTD) can be consider as the best drying method to
dry anchovy with higher quality compared to the open sun dryer (OSD) and forced
convective dryer (FCD) and this related to drying in shorter time with higher reduction
in weight, water activity, moisture content and color lightness with lower number of
microbes. The study is useful to seafood processors and policy makers to optimize fish
drying methods and make optimum usage of the fisheries stock in Oman. To reduce
contamination of commercial dried anchovies, selecting drying methods and other
appropriate facilities during and after drying need to be managed.
