Preliminarily Comparison of Nutritional Composition of Some Fresh and Processed
Processing made fish less susceptible to spoilage. Fish are rich in protein content but the protein content is reduced with processing gave a better result when long-time preservation was carried out. Aim of this study was comparison of proximate analysis of some fresh and processed seafoods. Raw materials and processed seafoods (canned mackerel tuna, frozen Sea-Bream and Pressed caviar) were obtained from different firms and analyzed. Analysis carried out according AOAC methods. Moisture, protein and fat values of tuna fish were estimated to be 51, 23.9 and 21.4%, respectively. In this study, moisture content of pressed caviar was 36%, protein content was 34.4% and fat content was 16.7%, carbohydrate and energy values were 4.9% and 316 kcal/100 g, respectively. Pressed and smoked seafoods contained lower amount of moisture but higher amounts of the other components than raw materials (p<0.05). Canned mackerel tuna, frozen sea bream and pressed caviar also contained higher amounts of fat, carbohydrate and energy, respectively (p<0.05) than raw material. Except canning with water, all processing technologies decreased the moisture content but increased energy values (p<0.05) of the fish. It is concluded that processed seafoods are rich in chemical components and very nutritive. Canned tuna with salted water may be advised for low-calorie diets. Caviar pressed was one the best sea foods that was produced in Iran. Since fishes are consumed as a major protein source in food, it is very important that the protein content should not be compromised during table preparation.
November 03, 2012; Accepted: December 16, 2012;
Published: March 04, 2013
Seafoods are very important for a healthy diet and it is popular to consume
these foods as raw, frozen, canned, smoked, marinated, salted and dried all
over the world. Processing presents consumer different tastes and minimizes
the waste of seafoods. It is also very important to increase shelf life of such
a perishable food since it leads to decrease economic losses. Therefore, a great
demand occurred to the seafood processing technology. Seafoods represent an
excellent option as a major source of nutrients and nutritional factors affecting
health, quality of life, general well-being and longevity. It is known that
98% of total mass of seafood flesh consist of water, protein and fat. However,
ratios of these components change due to the species of fish and processing
technology (Sikorski et al., 1990). Changes of
nutrient components in foods occurred due to the processing must be known since
they are important for human health (Birkeland et al.,
2004). The aim of this study was to determine the effect of processing on
the nutrient composition of seafoods. The most popular processed seafoods (canned
tuna, pressed caviar and frozen sea bream,) were analyzed before and after processing.
Aim of this study was comparison of proximate analysis of some fresh and processed
MATERIALS AND METHODS
Samples preparation: Selected fishes obtained from Persian gulf and Caspian sea from southern and northern of Iran. Raw materials and canned, frozen and pressed samples obtained in southern Iran, were subjected to analysis. With the exception of canned products; samples were transported to the laboratory in ice-boxes. One type of canned tuna (canned with vegetable oil) and other samples selected for study are popular in the market.
Techniques: All of the products were analyzed. Moisture content was
determined by drying sample at 105°C (Nuve FN500, Italy) to constant weight.
The difference of weight before and after drying was multiplied with 100 and
divided to the initial weight of the sample (AOAC, 1998a).
For the estimation of crude protein, Velp UDK 140 distillation unit and DK6
Heating digester (Velp Scientifica, Italy) were used according to Kjeldahl method.
Sample was heated with H2SO4 and a catalyst and then treated
with NaOH and boric acid. The amount of nitrogen was estimated after the titration
with HCl. It was multiplied with coefficient 6.25 (AOAC,
1998b). Fat was measured using Soxhelet system (AOAC,
1998c). Crude ash was determined by burning samples at 550°C (Nuve MF100,
Iran) (AOAC, 1998d). All analyses were performed in five
repetitions. Carbohydrate proportion was calculated mathematically (% carbohydrate
= 100-the total of other components) and energy value was calculated according
to the method of Merrill and Watt (1973). Data from the
different measurements were subjected to t test and statistical differences
were determined. The significance level was chosen as 0.05.
Statistical analysis: Experiments were performed in triplicate and results were expressed as Mean±SD and were analyzed by SPSS statistical programme.
RESULTS AND DISCUSSION
Canned tuna, pressed caviar and frozen sea bream were analyzed before and after
processing. The results of the samples obtained from different firms were presented
in Table 1 as mean values. Moisture, protein and fat values
of tuna fish were estimated to be 51, 23.9 and 21.4%, respectively. Sikorski
et al. (1990) presented the main components of Thunnus thynnus
as 67.7-72.6% moisture, 23.3-27.5% protein and 1.2-8.0% fat. Similarly Souci
et al. reported that the moisture, protein, fat and ash contents of tuna
fish after heat-sterilization process as 52.5, 23.8, 20.9 and 2.30%, respectively.
These results are similar to our results (Table 1). In this
study, moisture content of pressed caviar was 36%, protein content was 34.4%
(Fig. 1); fat content was 16.7%, carbohydrate and energy values
were 4.9% and 316 kcal/100 g, respectively, showing that moisture content decreased
while the other components and energy value increased (p<0.05) after caviar
pressing and packaging. Moisture content of the canned tuna with vegetable oil
(CVO) was (p<0.05) similar to the raw material. Energy and fat values of
canned tuna with vegetable oil (CVO) were significantly lower (p<0.05) than
the raw materials (Fig. 2, 3).
|| Protein contents of some selected seafoods
|| Fat contents of some selected seafoods
|| Nutrient composition of sea foods before and after processing
|CVO: Canned tuna with vegetable oil, Values are mean of three
||Energitic values of some selected seafoods
It is known that, heat-sterilization process affects the food components (Naczk
and Artyukhova, 1990) and fat content is different before and after canning
procedure (Ackman and McLeod, 1988). Freezed sea bream
are the other popular processed seafoods. Carbohydrate and energy values of
sea bream increased significantly (p<0.05) after the freezing process. Conversely,
moisture content decreased (p<0.05) as it expected. The moisture, protein
and fat amounts of raw caviar samples were determined as 46, 26.9 and 15%, respectively.
Protein and ash contents were highest in caviar. High ash content in caviar shows high minerals contents contain it, therefore, caviar contains high nutritive value in comparison others seafoods. Caviar is one of rare and nutritious seafoods in Iran.
Processed seafoods might be very nutritive, but not suitable for low-calorie
diets due to the high amounts of fat and energy. Canned tuna with salted water
may be advised for low-calorie diets. Caviar pressed was the best seafoods obtained
in Iran and in this study, because it contains highest protein value. The reactions
of water/oil with food items particularly at high temperature as obtained during
processing have been shown to affect some nutrients in the food item as well
as causing alteration of the structure of the oil and denaturing of the food
nutrients hence the significant difference recorded in moisture content after
the different processing method. Since fishes are consumed as a major protein
source in food, it is very important that the protein content should not be
compromised during table preparation. It is significant to note, therefore that
all the tables processing methods reduced the crude protein contents but the
reduction did not follow a particular order or fish type.
This project financially was supported by the Behbahan Technology University. Author wish to thank to Behbahan University, Iran for provide facilities.
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