الفهرس Only 14 pages are availabe for public view
 |  | from | 156 |  |  |
| | | from | 156 | | |
Abstract
5. SUMMARY
Fish is one of the major sources upon which the government depends in filling the gap between the production and consumption of animal protein. Bardwiel lagoon in North Sinia is one of the biggest sources of fish. And its production ranges between 2500 and 3000 tons per year. The Bardwiel lagoon is internationally famous for various fish species such as sea bass, sea bream and mullet, so, necessary measures should be taken to keep the lagoon as it is in order to guarantee the good quality of the fish.
The present study has three purposes:
1. To show how badly the traditional methods affect the quality of mullet coming form the lake.
2. To study the effect made by using some plants such as lupine and fenugreek on storing and keeping the Bardwiel fish on high quality.
3. To show how adding extract from lupine and fenugreek to ice during storage process can affect the chemical, natural, microbiological and sensory properties of mullet.
To achieve the above mentioned goals, this study has been implemented in two stages:
The first stage
In this stage, mullet, as the most widespread type of fish coming from Bardwiel lagoon, has been tested. Mullet has been divided into two groups:
The first group has been evaluated after zero time when it was in the market and has been brought to the laboratory under controlled conditions.
The second group has been stored by the traditional methods used in El-Arish market and has been compared to the group which was stored in laboratory under controlled conditions.
This has been studied by examining the chemical, natural, microbiological and sensory tests of this group of fish.
The second stage
The experimental study aimed to recognize the effect of adding lupine and fenugreek with concentration of 0.5% and 1% for ice on the shelf life for mullet fish which have been examined at the zero time and after 3, 6, 9, 12 and 15 days respectively and compared to the lab group which was stored under the same conditions by using ice alone. First, the species of both groups have been examined to evaluate the amount of moisture, fat, protein and ash. After that, the sensory, chemical and microbiological evaluation has been made.
The result indicated that, excellent and very good grades of any evaluation were for the samples stored at zero time of storage.
The formation of TVB – N increased with the time of storage and by the end of the storage period (day 6), a significant higher value (P < 0.05) was detected for TVB-N in market samples when compared with laboratory samples. However, the TMA values detected at the time of fish rejection was < 4 mg TMA-N/100g for both laboratory and market samples.
The TBA values have increased during storage period in both laboratory samples and market samples without any significant differences.
It was clear that, the total bacterial count, psychrophilic count and vibrio count in fish stored under laboratory conditions was lower than those of fish stored under market condition with significant differences (P < 0.05).
The sensory scores of mullet fish stored in ice made from water with different additives showed that, control samples lost its fresh seaweedy odour often the third day of storage but the skin was slight shiny and texture was firm with a score of 5.81 , whereas the fifth group which stored in ice made from water with 1% fenugreek concentration still had a seaweedy odour and other freshness characteristics with an average sensory score of 8.81. Additionally, the groups which were stored in ice with different additives prolonged for 15 days while the control group was spoiled at day 6.
The results indicated that, the pH values increased gradually in all treatments and this increase may be attributed to the production of volatile bases compounds by bacterial activity.
There were significant increases in total volatile bases nitrogen (TVB-N) and thiobarbituric acid (T.B.A) during storage period. There were significant differences (P < 0.05) between treatments starting from day 3 until the end of storage period. Since the TBA values in the range of 1-2 mg malonaldehyde /Kg of fish sample is usually taken as the limit of acceptability, the control samples have been discarded after day 3 of storage. The results also indicated that, there were significant differences (P < 0.05) between treatments and control after 0 time of storage and all treated fish TBA values maintained within the limit value (1-2 mg malonaldehyde /Kg) until day 12 of storage comparing to the control which increased after day 2 of storage.
Storing mullet fish in crashed ice with different additives (T 0.5%, T 1%, F 0.5%, and F 1%) significantly delayed the microbial growth and extended the shelf life of the product up to 12 days.
There was a little increase in moisture content during storage period and this may be due to uptake of solution inside the fish muscles as well as breakdown of amino and fatty acids. Also, there was a decomposition and degradation of nitrogen substances which may be due to the activity of microorganisms.
The results also showed little decrease in fat content during storage period and this decrease may be attributed to the breakdown of fatty acids.
The results also indicate that fish can not be sold as fresh after 3 days of storage in crashed ice. However, adding some additive such as lupine and fenugreek to the crashed ices can expand the storage period for a long time. This was clear with microbiological studies where there were significant differences between control and treated samples when total bacterial counts (TBC), psychrophlic counts (PTC) and vibrio counts have been enumerated.