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LIST OF TABLES
LIST OF ABBREVIATIONS
AIM OF STUDY
REVIEW OF LITERATURE
І. Definition of HACCP System
І.1: Hazard Analysis
І.1-1: Physical Hazard
І.1-2: Chemical Hazards
І.1-3: Biological Hazards
І.2: Critical Control Points (CCPs)
І.3: Monitoring Step
ІІ. Chemical composition of mullet fish
ІІ.1: Effect of Salting On
ІІ.1-1: Moisture Content
ІІ.1-2: Protein Content
ІІ.1-3: Fat Content
ІІ.1-4: Salt and Ash Content
ІІ.2: Quality criteria of salted fish
ІІ.2-1: pH value
ІІ.2-2: Total volatile bases nitrogen (TVB-N) Content
ІІ.2-3: Trimethylamine nitrogen (TMA-N) content
ІІ.2-4: Thiobarbituric acid(TBA) value
ІІ.3: Microbiological Hazards
ІІ.4: Sensory Evaluation
MATERIALS AND METHODS.
І.1: Fish samples
І.2: Edible salt
І.3: Plastic containers and polyethylene bags
І.4: Dry salted technique
ІІ. Analytical Methods
ІІ.1: Physico-Chemical Parameters
ІІ.1-1: Moisture Content, Crude Protein, Fat, Ash and Sodium Chloride Content
ІІ.1-2: pH Value
ІІ.1-3: Total Volatile Nitrogen (TVN) Content
ІІ.1-4: Trimethylamine Nitrogen (TMA-N) Content
ІІ.1-5: Thiobarbituric Acid (TBA) Value
ІІ.2: Microbiological Analysis
ІІ.2-1: Total Viable Count
ІІ.2-2: Halophilic Bacterial Count
ІІ.2-3: Yeasts And Molds Count
ІІ.3: Sensory Evaluation
ІІ.4: Statistical Analysis
RESULT AND DISCUSSION
PART І: Hazards Analysis (HA) of raw mullet fish samples collected from local landing center (Shakshouk, Fayoum) Qaroun Lake..
І.1: Raw Mullet Fish Samples
І.1-1: Hazards Analysis (HA)
І.1-1-1: Sensorial hazards analysis (HA)
І.1-1-2: Chemical hazards
І.1-1-2-1: Proximate chemical composition
І.1-1-3: Biochemical hazard analysis
І.1-1-4:Microbial hazard analysis
PART ІІ: Salted mullet fish products during ambient storage periods for 105 days..
ІІ.1: The organolyptic evaluation of salted mullet fish during storag
ІІ.1-5: Overall Acceptability
ІІ.2: Hazard Analysis (HA) of chemical composition
ІІ.2-1: Moisture content
ІІ.2-2: Protein content
ІІ.2-3: Lipid content
ІІ.2-4: Ash content
ІІ.2-5: Salt content
ІІ.3: Biochemical hazard analysis of salted mullet fish during ambient storage periods for 105 days ..
ІІ.3-1: pH value
ІІ.3-2: Thiobarbaturic acid (TBA) value
ІІ.3-3: Total Volatile Bases Nitrogen (TVB-N) content
ІІ.3-4: Trimethylamine Nitrogen (TMA-N) Content
ІІ.4: Microbiological hazard analysis of salted mullet fish treatments during ambient storage periods for 105 days....
ІІ.4-1: Total viable count (TVC)
ІІ.4-2: Halophilic bacterial count (HBC)
PART ІІІ: Critical Control Points (CCPs).
ІІІ.1: Dry salted whole mullet fish
ІІІ.2: Dry salting level
ІІІ.3: Storage temperature
ІІІ.4: Preliminary washing preparation steps and packing
ІІІ.5: Monitoring steps
Firstly and lastly, all praise be to ALLAH (Al-Mighty), The beneficent, The Merciful, without Whose mercy and guidance this work would never have been started nor completed.
I wish to express my highest appreciation and deep obligation to Prof. Dr. Nabil El Sayed Hafez, Prof. of Food Science and Technology, Faculty of Agriculture, Fayoum University.
My deepest thank due to DrAwad Abd El Tawab Awad, Head of Food Science and Technology Department, Faculty of Agriculture, Fayoum University for his supervision and great helping in the practical work.
I would like to express my grateful and very much indebted to Prof. Dr. Sayed Mekawy Ibrahim, prof. of Fish Processing Technology, National Institute of Oceanography and Fisheries, for his supervision and scientific advices throughout the preparation of this work.
Deep appreciation for Dr. Shaaban El Shreif, A head of Shakshouk Fish Research Station Fayoum, National Institute of Oceanography and Fisheries and all the members of station for the great support and help during this study.
Finally, I wish to express my warmest thanks to my Parents, Brothers, Sisters and my Wife for their patience, continuous encouragement and pushing me for completion of this work.
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LIST OF FIGURES
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Hazard Analysis Critical Control Point (HACCP) is a management tool aimed at controlling food borne safety hazards, and used as a systematic way of identifying potential public health hazards in the food industry, assessing those hazards and ultimately controlling them. HACCP is the international wide known safety system, which has proved its efficiency in all the food industry’s sectors and on the entire food chain. Also , it is a systematic interactive scientific method of identification, evaluation and control of the risks associated with the food. HACCP strategy is based on the introduction of a new system of prevention, elimination or minimizing the risks at acceptable levels by taking into account all the hazards, which may affect the consumers’ security (Ehiri et al., 1995; Belton, 1999 and Curtis, 2005).
The concept of HACCP was launched with the early stages of the space program in the 1950s. The Pillsbury Company, the U.S. Army Laboratory in Natick, Massachusetts, and the National Aeronautical and Space Association (NASA) developed the foundation of HACCP as a way to ensure the safety of food produced for astronauts. Given the impracticality of testing all of the foods produced and using inspection-based systems that could not guarantee safe food 100% of the time, this coalition introduced the approach of building safety into the food manufacturing process in 1971 (Stevenson, 2006).
HACCP (pronounced “has-sip”) is a food safety system that prevents disasters; the system has seven principles; conduct a hazard analysis, determine Critical Control Points (CCPs), establish critical limit(s), establish a system to monitor control of the CCP, establish the corrective actions, establish procedures for verification and establish documentation. HACCP helps prevent food borne illness outbreaks because HACCP is a proactive approach to controlling every step in the flow of food. Simply stated, the HACCP goal is to stop, control, and prevent problems that impact the safety of food. HACCP is a written food safety system to enable the selling and serving of safe food (Wiley and Sons, 2007).
The application of HACCP system and guidelines was recommended by Codex (1997); it has been progressively introduced and applied for the benefit of the food industry. However, the hazard analyses conducted by most food industries are often ineffective and unsuccessful (Ryu et al., 2012).
For application of HACCPs in fish salting it must be understand the operational steps of this method. Salting is one of the oldest techniques known to man for the preservation and increasing of shelf life of fish, and was in use long before other processes such as smoking, drying, canning, marinating, etc. Fish when are not consumed fresh; various methods of preservation particularly salting, drying, smoking, frying and freezing are normally used. However, salting followed by drying is very common because it is cheaper, does not need sophisticated equipment and is easily adaptable by local processors. In addition, salted fish products are popular in many countries around the world. Salted fish products have been shown to be safe for millenniums, even in developed countries (Turan et al., 2007 and Sobukola and Olatunde, 2011).
Salting techniques are simple and involve salt crystals or brine. There are three types of salting of fish: dry salting, wet salting and a combination of the two methods. Length of salting period as well as salt concentration depends on the expected final product. Salt uptake depends on many factors including the quality and chemical composition of raw material, species, muscle type, fish size, fillet thickness, weight, physiological state, salting method, brine concentration, duration of salting process and fish to salt ratio (Wang et al., 2000; Jittinandana et al., 2002; Barat et al., 2006; Bellagha et al., 2007; Gallart-Jornet et al., 2007). These factors could subsequently affect the quality as well as further processing such as drying and storage.
Therefore, the main objectives of the current study can be summarized in the following items:
1- Identifying the potential physical, chemical and microbial hazards associated with fish salting at any step along the processing steps; from primary receiving, processing, storage and until the point of consumption.
2- Determination the CCPs throughout different operational steps that can be controlled to reduce the hazards or minimize it.
3- Monitoring the control of the CCPs and the action that must be taken when a particular CCP is not under control.
4- Record recommendations of the principles and application of HACCP system in fish salting under the local conditions.
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HACCP is the international wide known safety system, which has proved its efficiency in all the food industry’s sectors and on the entire food chain. HACCP is a systematic interactive scientific method of identification, evaluation and control of the risks associated with the food. HACCP strategy is based on the introduction of a new system of prevention, elimination or minimizing the risks at acceptable levels by taking into account all the hazards, which may affect the consumers’ security (Belton, 1999).
HACCP is also a preventive system of quality control and was developed to minimize consumer risk of illness and injury from foods. Its goal is to prevent the hazards at the earliest possible stage of food processing. It enables food processors to identify, prioritize and minimize various likely hazards. It enables consideration of all the factors that contribute to most outbreaks and of risk-assessment techniques. HACCP treats the production of food as a total continuous ‘system’ assuring food safety from harvest to consumption. Potential benefits include improvement in quality and lowered costs of manufacturing. The system is broken down into components and each component is evaluated. The application of HACCP allows the management to control any area or point in the food system that could contribute to a hazardous situation (Kanduri and Ronald, 2002).
HACCP system allows companies to prevent hazards from occurring in the first place, instead of relying on end-product testing to determine whether the hazards have already occurred (Curtis, 2005). In addition, HACCP helps prevent foodborne illness outbreaks because HACCP is a proactive approach to control every step in the flow of food (Wiley and Sons, 2007).
The application of HACCP system and guidelines was recommended by Codex (1997); it has been progressively introduced and applied for the benefit of the food industry. However, the hazard analyses conducted by most food industries are often ineffective and unsuccessful (Ryu et al., 2012).
A hazard is defined as a biological, chemical or physical agent in, or condition of food that has the potential to cause an adverse health effect. A significant hazard is a hazard (or a hazard in combination with other hazards) that is such a nature that its elimination, control or reduction to a significant level is essential to the production of safe food.
USDA, (1999) united states departmentof agreculture reported that preventive measures are the physical, chemical, or other means that can be used to control a food safety hazard. More than one preventive measure may be needed to control a food safety hazard and more than one food safety hazard may be controlled by a specific preventive measure.
Curtis, (2005) mentioned that the purpose of the hazard analysis is to develop a list of significant hazards that are reasonably likely to cause harm, if not controlled. Physical, chemical and microbial hazards (covering aspects such as product ingredients, characteristics, processing procedures, plant design, equipment, food security and microbial content) should all be considered.
Schmidt, et al. (1997) reported that physical hazards include: inadvertent field matter (stones, metal, insect fragments, etc.); inadvertent processing residues (glass, metal fragments, etc.); intentional materials (employee sabotage) and miscellaneous particulates and fragments.
A physical hazard is a physical component of a food that is unexpected and may cause illness or injury to the person consuming the food. Foreign materials such as glass, metal, or plastic are familiar physical hazards in meat and poultry products, usually found because a process or a piece of equipment has not been properly controlled while the food was being produced (USDA, 1999).
Physical hazards: Any material in the food that is not normally associated with it is considered as foreign material. Examples of physical hazards include glass, wood, staples, insect fragments, rodent filth, personal effects such as jewelry, band-aids, cigarette butts, etc.(Kanduri and Ronald, 2002). AQIS (2005) Austranan Quarantine and Inspection Service reported that the purpose of the hazard analysis is to systematically identify and list all the potential hazards at each step of processing. The hazard analysis is also used to determine which potential hazards are significant – that is – which hazards – if not controlled are likely to impact on public health and safety.
Physical agents may bring physical hazards, these include; stones, glasses, metallic materials, bones and plastic materials (TFDA, 2005).
A physical hazard is any physical material or foreign object not normally found in a food that can cause illness and injury. These physical hazards may be the result of many points in the food chain from harvest to consumer, including those within of contamination, carelessness, mishandling, or implementing poor procedures at the food establishment. These hazards are the easiest to identify because the consumer usually finds the foreign object and reports the incident (Wiley and Sons, 2007).
Clute (2009) showed that the risks are usually the easiest to remove because they are the easiest to see with the naked eye. Also, Bucknavage andCutter, (2009) pointed out that physical hazards are typically hard or sharp objects that result in injury to the person who consumes the product. The most common examples of these hazards are glass, metal, plastic, stones, shells, wood, and bones.
A chemical hazard is a substance found in the food that is either poisonous or deleterious; these are classified either as natural, or as due to human intervention causing intentional or unintentional addition to the food product (Kanduri and Ronald, 2002). Chemical contaminants in food may be naturally occurring or may be added during handling and processing of food. Harmful chemicals at high levels have been associated with acute cases of food borne illnesses and can be responsible for chronic illness at lower levels (TFDA, 2005).
Also, chemical hazards may also cause food borne illness. Chemical hazards may occur naturally or may be introduced during any stage of food production. Dangerous, naturally occurring chemicals can be found in some species of fish (Scombroid, Ciguatera, and Puffer Fish) or shellfish (Molluscan, Lobsters, and Red Rock Crabs), some plant foods (Red Kidney Beans), or mushrooms, and allergens (Wiley and Sons, 2007).
The chemicals added intentionally can be associated with raw materials or used as an ingredient or an aid in processing. Chemicals such as pesticides, fungicides, fertilizers, or antibiotics may be added to the raw products during production or growth, and if not controlled, can become a hazard with that raw material. Ingredients such as preservatives, coloring agents, additives, processing aids, and some vitamins may become a hazard when their addition to the process is not controlled (Bucknavage and cutter, 2009).
A chemical hazard is defined as any chemical in the ingredient or packaging that may contribute to a food safety issue or may be a health hazard. Traditionally, these are chemicals such as pesticides on vegetative ingredients and non-GRAS (generally recognized as safe) chemicals such as food additives contained within imported ingredients or as undeclared components within flavors (Clute, 2009).
Hazard identification gives a qualitative indication of the potential microbial hazards arising from the consumption of a particular food product. Information on potentially hazardous bacteria can be obtained from, e.g. surveys of the microbial composition of raw materials and from epidemiological surveillance of food borne infections and intoxications (Richmond, 1991 and WHO, 1992). These include microbiological organisms such as bacteria, viruses, and fungi. Other biological hazards are parasites. These organisms are commonly associated with humans and with raw products entering the food establishment. Most microorganisms are killed or inactivated by cooking, and numbers can be minimized by adequate control of handling and storage practices. Viruses can be food borne/water-borne or transmitted to food by human, animal or other agents (TFDA, 2005).
Scott (2006) showed that biological hazards are comprised of bacteria, viruses and parasites that cause illness through infection and/or intoxication. Improper storage and holding temperatures, inadequate cooking temperature(s), poor personal hygiene, cross-contamination, and improper reheating facilitate the growth of food borne bacterial pathogens and spoilage organisms.
Bucknavage and Cutter (2009) mentioned that control of biological hazards begins with the prevention of contamination in raw materials. For a food-processing establishment, control may be met through receipt of a certificate of analysis, letter of guarantee, or another form of assurance issued by the supplier. Numerous process control procedures (e.g., cooking, cooling, or changing product characteristics through drying or fermentation.) may be employed.
Clute (2009) showed that bacteria, yeasts, molds, and sometimes their end products, such as toxins, are found in many forms throughout the growing, harvesting, manufacturing, and distribution environments. Pathogens are all extremely dangerous and harmful to human and serious care must be taken by the HACCP team to ensure that they are all excluded or killed during processing.
The microbial status of seafood after catch is closely related to environmental conditions and microbiological quality of the water. These factors include water temperature, salt content, distance between localization of catch and polluted areas (containing human and animal feces), natural occurrence of bacteria in the water, ingestion of food by fish, methods of catch and chilling, and post-harvest handling or processing conditions(Feldhusen, 2000).
A CCP is defined as a point, step or procedure where a food safety hazard can be prevented, eliminated or reduced. Examples of CCPs may include, but are not limited; to chilling, cooking, prevention of cross-contamination and certain aspects of employees and environmental hygiene (Kanduri and Ronald, 2002).
A critical control point is defined as a step at which control can be applied and is essential to prevent or eliminate a food safety hazard or reduce it to an acceptable level. Critical control points are located at any step where hazards can be prevented, eliminated, or reduced to acceptable levels. Examples of CCPs may include: thermal processing, chilling, testing ingredients for chemical residues, product formulation control, and testing product for metal contaminants. CCPs must be carefully developed and documented. In addition, they must be used only for purposes of product safety. For example, a specified heat process, at a given time and temperature designed to destroy a specific microbiological pathogen, could be a CCP (Hui et al., 2003). There are two types of CCPs namely CCP1 which assures control of the hazard by eliminating it whereas CCP2 will only minimize it but cannot assure control of a hazard since the hazard is only minimized, reduced or delayed. Examples of CCP1 include retorting of meat, pasteurization of milk. Examples of CCP2 include refrigeration and proper cleaning (TFDA, 2005).
A Critical Control Point (CCP) is defined as a factor, practice, procedure, process or location that can be controlled in order to prevent, control, eliminate or reduce a hazard, or minimize the likelihood of its occurrence. In simpler terms, a CCP can be considered as a step that if no control is applied, then the food is likely to be unsafe (AQIS, 2005). A CCP is differentiated from a control point (CP) in that a CP is any step at which a hazard is controlled, but is not necessarily essential to the safety of the product. In other words, loss of control at a CCP will result probably in an unsafe product (Wiley and Sons, 2007). After the process flow diagramming and the hazard analysis are complete, the next step toward the development of the HACCP plan is to determine the critical control points. These are defined as points within the process at which a physical, chemical, microbiological, or allergen hazard can be controlled, removed, or prevented from entering the process as a means of ensuring the safety of the food (Clute, 2009).
Critical Control Points (CCPs) are those steps of the process that are essential to prevent or eliminate food safety hazards or reduce them to acceptable levels. The identification of CCPs requires professional judgment and may be aided by the application of a decision tree. For each process step in the flow diagram the team must determine whether this step is a Critical Control Point for each hazard identified. In general, control measures applied at a CCP require frequent monitoring to ensure that the hazard is controlled effectively (Stanley et al., 2011).
Monitoring is a scheduled observation or measurement of a CCP and its limits. The purpose of monitoring is two-fold: to assess whether a CCP is under control and to produce an accurate record for future verification and validation. Monitoring CCPs is of great importance and should be done by responsible individuals who are properly trained, have commitment to HACCP and are unbiased. Monitoring procedures should be accurate and done at appropriately (Schmidt et al., 1997). Monitoring is a planned sequence of observations or measurements which may be either qualitative or numeric to assess whether a CCP is under control, and to produce an accurate record for future use in verification. Examples of measurements for monitoring include physical aspects such as visual observations, sensory analyses, chemical analysis, microbiological indices, temperature, time, pH, moisture level, etc. Monitoring requires knowledge in sampling, based on appropriate statistical procedures (Kanduri and Ronald, 2002).
Typical monitoring procedures include checking temperatures, pH values and moisture levels. Monitoring procedures are most helpful when they are rapid and easy to carry out. Monitoring can be as simple as an operator monitoring product temperature, or more complex such as an operator conducting an in-line pH test using a pH meter to measure acidity or alkalinity (Curtis, 2005).
Monitoring is the scheduled measurement or observation of a CCP relative to its critical limits. The monitoring procedures must be able to detect loss of control at the CCP. Further, monitoring should ideally provide this information in time to make adjustments to ensure control of the process to prevent violating the critical limits. If monitoring is not continuous, then the amount or frequency of monitoring must be sufficient to guarantee the CCP in control. Most monitoring procedures for CCPs will need to be done rapidly because they relate to on-line processes and there will not be time for lengthy analytical testing. All records and documents associated with monitoring CCPs must be signed by the person(s) doing the monitoring and by a responsible (TFDA, 2005).
The monitoring procedures determine and document whether the critical limits are being met. The HACCP team must answer the questions of what will be monitored, how it will be monitored, when it will be monitored, and who will monitor it. With regard to what will be monitored, regulatory requirements state that all CCPs must be monitored and CLs be identified (Gombas et al., 2006).
Monitoring enables the manager to determine if the team is doing its part to serve and sell safe food. Monitoring also helps to identify problems in your food service operation. Monitoring provides tracking for your food safety management system throughout the operation (Wiley and Sons, 2007). Bucknavage andCutter, (2009) noticed that an important characteristic of monitoring is whether it is continuous or discontinuous. The monitoring task must be completed at its set frequency by the person designated to perform it. If a task is too difficult or if the person is not able to perform it at the specified times, the resulting lapses will constitute a process deviation.
Fish occupies one of the foremost placed among the food products of animal origin in nutritive value because of the presence of valuable proteins, easily assailable oils, rich in vitamins and various kinds of mineral substances. Besides, the meat of fish contains glycogen, enzymes and vitamins, although in relatively small quantities. Chemical composition of fish depends upon its species, age, sex, size, the fishing season, state of reproductive cycle, the availability of food in the water, the habitat and other environmental factors (Zaitsev et al., 1969 and Windsor and Barlow, 1981).
The chemical composition of raw Mullet fish (Mugil cephalus) was determined by several authors. It was around 70% moisture, 19% protein and 9.5% total lipid on wet weight as mentioned by IwasakiandHarada(1985). Mullet fish is considered as one of semi fatty fish species. Its lipid content ranged from 5.6% to 9.4% as reported by Khallaf (1986) and Hearn et al., (1987). One of this species (Mugil cephalus) contained about 5.06% fat (Viswanathan-Nairand Gopakumar, 1978). Shalaby (1990) found the chemical composition (wet weight) of Mullet fish samples were 77.18% moisture, 15.63% crude protein, 5.82% lipid and 1.36% ash content.
Grey Mullet (Mugil cephalus) is one of the most widely distributed food fish in the world. It is found in coastal waters and estuaries throughout the tropics and subtropics (Hsu and Deng, 1980).
Flathead grey Mullet (Mugil cephalus L.) is one of the Mullet species which is a coastal migratory fish and important for food and roe. It is principal economic fish of Aegean Sea and consumers prefer it for nutrition. Especially Mullets caught from the lagoon have very delicious taste. Flathead grey Mullet usually live in sea and is very durable to ecological factors (as salinity, oxygen, etc.) except cold water. During the summer, flathead grey Mullet migrates to coastal waters, enter small bays and harbors containing abundant food, whereas it migrates to deep waters in winter. Its primary foods are molluscs, algae and water plants on the sea bed. Spawning period of flathead grey Mullet is comparatively long; from June to August (Balik et al., 1992).
Yasin, (1997) found that the approximate composition (dry weight) of raw Mullet fish was 72.64% moisture, 80.89% protein, 14.50 fat, and 4.27% ash content. Rehbein and Oehlenschlager (2009) found that the gross composition (wet weight) of raw Mullet fish was 77% moisture, 19% crude protein, 3.8%lipid, and 4.27% ash .
Aman (1983) studied the effect of salting on Mullet fish meat (Mugil cephalus) and found that moisture decreased from 78.31% in fresh fish to 67.15% after six weeks of brining. Wheaton and Lawson (1985) determined the water content and changes in weight of split fish with different types of cure strength. They found that moisture content were 72-74% with 16-18% loss in weight for the light salting, 63.70% with 20-26% loss in weight for medium salting and 57.5% with 30% loss in weight for heavy salting.
Rashad (1986) reported that moisture content in lightly salted Mullet fish decreased slightly during the first week of salting and reached maximum decline on the third week. While it remained constant at the end of salting process.
Yasin (1997) observed a progressive loss in moisture content of Mullet accompanied with slight increase in protein and lipid level. Hegazy, (1998) reported that moisture continuously decreased either after brining or cold-smoking processes and storage period for 120 days at 4 c of both common Carp and Herring species.
Awad (1999) noticed that the moisture content of the finished product of salt-cured fish in parallel with the water activity plays an important role in the determination of keeping quality or shelf life of such product in addition to the salt content.
Hernandez-herrero et al., (1999) found that after the salting process of anchovy, the moisture content decreased from 75.5% in fresh fish to 54.16% in salted fish and the loss in moisture content was accompanied by increase in the salt and ash contents. The decrease in moisture content and increase in the salt and ash of salted anchovy were significant only during the first week of ripening.
Unlusayin et al., (2010) found that the changes in moisture contents of fresh and brine salted rainbow trout were given moisture in muscle in fresh was 76.59% and75.02% in brine salted 8% and 75.06% in brine salted 20 % and 69.77 %(w/w) in dry salted fish samples.
Yasin (1997) found that crude protein decreased by 6.7% (dry wt.) when the Mullet fish brined in 20% NaCl for 48 hr at 20◦C. Also, Hernandez-herrero et al., (1999) Found that the protein content in anchovy muscles decreased markedly after six weeks from 20.44% to 17.81%. The protein content in brine remained constant after six weeks and then decreased appreciably until the end of the ripening (0.94 to 0.56%).
In salted fish, where the salt concentration reaches 20% (Thorarinsdottir et al., 2002), high ionic strength causes contraction of the myofibrils (Offer and Knight, 1988) and dehydration of the proteins in a process known as ‘‘salting out’’ (Kelleher and Hultin, 1991 and Stefansson and Hultin, 1994). Also, the pH of the medium and the type of salts used for salting can influence the degree of protein denaturation (Kinsella, 1982 and Morrissey et al., 1987), thus affecting protein functionality to a greater or lesser degree.
During the salting process, the changes in protein structure such as protein denaturation of cod occurred when brine concentration was raised from 20 to 25% due to the protein salting-out and the yield got lower than that obtained when using 20% brine (Barat et al., 2002).
Martinez-AlvarezandGomez-Guillen(2006) reported that salting entails loss of water and uptake of salt. This affects the conformation of the muscle proteins, causing changes in water-holding capacity (WHC) and subsequent protein denaturation. Martinez-AlvarezandGomez-Guillen(2006) found that dry-salting reduced the water-holding capacity(WHC) of the muscle, from 3.32 g water retained/g protein in unsalted cod to final values ranging from 1.95 to2.33 g water retained/g protein in dry salted fillets.
Unlusayin et al., (2010) found that the total protein values of fresh, brine salted and dry salted rainbow trout and extracts were given protein in muscles in fresh was 76.53% and 73.31% in brine salted 8 % and 72.47% in brine salted 20 % and 71.29 %(w/w)(w/w)in dry salted rainbow trout.
An increase in the protein content in the salting medium was found during wet salted Tilapia production. Also, the protein was solubility to a greater extent when the salting time increased. The increase in the soluble protein content was primarily due to the salting-in effect. The ionic strength of NaCl solution used as a brining medium was approximate 4.27. This ionic strength resulted in the solubilisation of both sarcoplasmic and myofibrillar proteins especially with increasing salting time. At the ionic strengths >0.15, the inter-fibrillar spaces become larger due to electrostatic shielding effect from salt ions binding to charged parts of the filaments (Chaijan, 2011 and Thorarinsdottir et al., 2011).
The rancidity of salted fish, which negatively affect the quality of the finished product, was found to increase according to many factors such as: time of salting, fish species, oil content, degree of unsaturation of oil, presence or absence of haematin pigments and presence or absence of sunlight (Del Valle et al., 1973). Fish body oils are very susceptible to oxidation by atmospheric oxygen leading to rancid off flavors. Such undesirable flavors decrease the acceptability of the fish product, there is some degree of rancidity is considered normal (FAO, 1981).
Total lipid content is highly variable in fish ranging from under 0.6% in cod to a reported 25.5% in Mackerel. In addition to species variability; lipid content varies with anatomical, sex, season and diet (Jacquot, 1961 and Love, 1970).
Martinez-Alvarezand Gildberg (1988) found that the decreasing oil yield may be due to enzymatic spoilage of the fish lipids. This spoilage converts triglycerides and phospholipids into free fatty acids and other products such as oil-soluble di- and monoglycerides and water soluble phosphate esters.
El-Sebaiy and Metwalli (1989) found that the lipid content of salted fermented Bouri fish decreased accompanied by an increase in peroxide value and production of free fatty acids. El-Sharnouby (1989) reported that the total lipids content of fish decreased as a result of salting and curing process. The decrease in lipid contents may be attributed to the hydrolysis of triglycerides and phospholipids, which is catalyzed by lipases and phospholipases and release of free fatty acids that is soluble in water then leaching into the drip (Aman and Shehata, 1978 and Al-Habib and Al-Aswad, 1985).
The higher loss in lipid content of dried Mullet may be due to more protein denaturation as a result of high content of salt in tissues to an extent that may cause decrease in water holding capacity (WHC) and emulsifying properties of proteins (Yasin, 1997). Hernandez-herrero et al., (1999) observed that the content of anchovy from fat remained constant (3-5) during the ripening process, although slight variability was apparent. The fat content of anchovy was 3.24 in fresh fish and 3.74, 3.45, 4.87, 3.55, 4.22, 4.60, 4.87, 4.70 and 4.79% after 1, 2, 3, 4, 5, 6, 7, 8 and 9 weeks of salting anchovy, respectively.
Unlusayin et al., (2010) found that the changes in fat content of fresh and brine salted rainbow trout were given fat in muscle in fresh was 13.75% and 12.11 % in brine salted 8 % (w/w) and 12.87 % in brine salted 20 % (w/w) and 11.46 % in dry salted rainbow trout.
Jittinandana et al., (2002) reported that higher brine concentration caused dehydration of the fillets, due to the difference in solute concentration between the brine solution and the inherent muscle water; water migrated from fish muscle to the high brine solution. The increase in salt content in the muscle resulted in a decrease in the Aw of muscle. Increased water phase salt content corresponded with decreased Aw and increased product ash content. Increased salt content promoted protein–protein interactions and decreased protein–water interactions . Salt preserves the fish by dehydrating tissue, increasing water phase salt, and decreasing Aw.
The final salt concentration in the different dry salted samples, expressed chiefly as % ash, did not generally correlate with the concentration in the corresponding brined samples (Martinez-Alvarez, 2003).
The yield or the weight gain of salted products depends not only on the brine concentration, but also on the brining time and temperature. The weight gain of salted Herring at low brining temperature was higher than that at high brining temperature and increased weight gain seemed possible by further extension of the brining time (Birkeland et al., 2005).
Heredia et al., (2007) reported that NaCl present in the product would be located in the liquid phase at a saturation concentration. Since the saturated brine concentration is around 25 %( w/w), the evaporation of three units of water implies the formation of one unit of NaCl crystals. Salting involves salt intake with a saturation of the liquid phase. During the drying process, the saturation of the cod liquid phase would be maintained by the precipitation of the NaCl, thus forming salt crystals, mainly on the cod surface.
Bellagha et al., (2007) found that the rate of salt uptake was different whether Sardine fish salting was made by brining or by dry salting. Thus, during the first four salting hours, and for both salting methods, the rate of salt diffusion in the fish flesh were high, although much higher in the dry salting case. After 24 h salting, salt content increase to a constant of 31% (db) for brining method, and of 45% (db) for dry salting. Berhimpon et al., (1990) found a salt content equal to 34% (db) when salting yellow tail (Trachurus mcullochinichols) in 21% brine.
Bellagha et al., (2007) reported that However, the equilibrium salt uptake was not reached before 50 h. although dry salting gives the most rapid rate of reduction in moisture content and the lowest final moisture content during salting, it also gave a slower rate of reduction of moisture and higher final water content during drying. Hence water content at the end of the drying period is less important for brined fish at 21%.
When salt brine or dry salt are used as salting agents, two main simultaneous flows are usually generated; water loss and salt uptake. The salt uptake and water loss depend on the contact area and initial weight (Fuentes et al., 2007). Fuentes et al., (2008) found that NaCl content of the salted sea bass fillets increased throughout the salting process, with the highest increase for salt concentration on dry basis, since during the process besides the incorporation of solutes into the muscle, osmotic dehydration occurs. Water from the fish muscle goes out to the salted sea bass fish surface during the salting process, due to the effect of salt as dehydration agent, dissolving the sodium chloride present in the surface. Consequently, brine is formed on the fillet surface. Some of the salt from this brine penetrates into the fish flesh; while some of the brine drips on the trays where the fish fillets are placed.
Chaijan (2011) found that salt penetrate into the Tilapia muscle by dialysis mechanism whereas water diffuses out of the muscle by the osmotic pressure . The salt content in dry salted Tilapia muscle was higher than that in wet salted Tilapia muscle during the first 10–60 min of salting. This was due to the difference in salt concentration used among the wet and dry salting process. Dry salting used the crystal salt covered directly on the fish surface. This resulted in a greater difference in the concentration of salt between inside and outside of the muscle. Therefore, the salt can penetrate into the flesh effectively. The wet salting using 25% salt as a salting medium showed the lowered rate of salt uptake when compared to the dry salting process. From the result, the salt content of the products processed with dry salting was greater than of those soaked with salt solution for the same salting time up to 60 min. However, no difference in the salt content in fish muscle of both wet and dry salting was found after 180 min of salting. This was probably due to the balance of the salt content between the internal part of the muscle and the surrounding brine/crystal salt in both salting processes. Diffusion occurs until the sodium chloride concentration of the system (fish and brine) has equilibrated . A gradual increase in the salt content in wet salted fish was observed with increasing salting time from 0 to 180 min. This result indicated the spontaneous uptake of salt by the muscle. Dry salting with a greater difference in the salt concentration between inside and outside of the muscle led to the higher penetration rate of salt into the muscle during the first 30 min. Thereafter, the rate of salt uptake of dry salting process tended to equilibrium resulting in the constant salt content in the muscle .
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