CHAPTER ONE

INTRODUCTION

1.1 Back Ground Of The Work

Classification1 is an important tool used by scientists to show how organisms are related to each other and to group them by their characteristics, but this can be difficult for some marine organisms!

Linnean classification system

In the 18th century, Carl Linnaeus published a system for classifying living things. This developed into the modern classification system, which is still being debated today. Some scientists view kingdom as the highest grouping, while others argue that kingdoms should be grouped further, into domains. Classification involves grouping organisms into a series of hierarchical categories: kingdom2, phylum3, class4, order5, family6, genus7 and species8. These categories were first developed by Carl Linnaeus in the 18th century and have remained in common use ever since.

Naming organisms

Dr Peter Buchanan and Dr Robert Hoare, of Manaaki Whenua – Landcare Research, introduce the classification system that scientists use to identify and name organisms. However, there is significant debate amongst scientists about the groupings of organisms within these categories. For example, when Linnaeus first described his system, he named only 2 kingdoms – animals and plants. Today, most scientists recognise at least 5 kingdoms, some argue that there are at least 10 and others debate the value of a further category, called a domain, that would sit above kingdom.

Six kingdoms of marine organisms

All kingdoms are represented in the marine environment, and most scientists classify marine organisms into one of the following 6 kingdoms.

• Bacteria are single-celled organisms that reproduce by splitting in two. Bacteria9 live throughout the marine environment. They play a crucial role in ecosystems10, breaking down organic11 material and making nutrients12 available for the phytoplankton13.
• Protozoans are single-celled organisms that are generally much larger than bacteria. They may be autotrophic14 or heterotrophic15. In the marine environment, this kingdom is well represented and includes amoebae.
• Chromists range from very small organisms such as diatoms16 (a type of phytoplankton) to seaweeds. Most chromists photosynthesise17 but there are some significant differences that have led scientists to classify them separately to plants, for example, they use a different kind of chlorophyll18.

Phytoplankton

Phytoplankton are important primary producers in the marine food web. They are microscopic, single-celled organisms that float freely in the ocean. They rely on energy from the sun for photosynthesis and are therefore most commonly found less than 100 metres below the surface. Phytoplankton are eaten by zooplankton.

These are diatoms, under the microscope. Diatoms are one of the most common types of phytoplankton.

• Fungi rely on breaking down organic material as they are not able to make their own food. There are very few fungi19 in the marine environment.
• Plants are multi-cellular and autotrophic – they use photosynthesis20 to produce food using sunlight. Plants are much more widespread on land and in freshwater, and there are only a few types that thrive in the marine environment, for example, eel grass and mangroves. Seaweeds were previously classed as plants before they were reclassified as chromists.
• Animals are typically large and multi-cellular. They are heterotrophic and rely on other organisms for food. Animals in the marine environment include jellyfish, sponges, sea spiders, bryozoans, mussels, sea stars, fish and whales

At the seafood industrial level, several methods can be used to evaluate the quality of the products to ensure that qualitative parameters are met by all agents in the value chain (producer to final consumer), including regulatory agencies, as well as in different stages of fish processing [8]. It is known that no single method is reliable enough to determine the freshness or quality of seafood products [6]. On the other hand, different species and products spoil in different patterns, and the use of appropriate assessment methods is needed.

Apart from sensory methodologies, physical, chemical, and microbial methods have been developed [8][9][10]. However, most of them have as fundamental base sensory knowledge to associate the analytical results with overall quality. The pH of distilled water, controlled before use, was between 7-7.4. Analyses were performed at 0, 2,5,8,12,14,15,17,

Fish and fish-based products are easily perishable foods due to different factors, including fragile organization, abundant endo-enzymes, psychrophilic bacteria, and impact of pre-harvest operations, that contribute to reducing its value. Therefore, a timely effective method for fish freshness and shelf-life evaluation is important

Fish quality is a complex concept, including a range of factors, which depend on consumers’ quality perception, market preferences, storage conditions, microbial load and activity, etc. However, freshness is the most important quality attributes and control methods for the fish sector. Many traditional methods have been used to monitor freshness and other quality changes occurring in fish during their storage (Hassoun & Karoui, 2015a; Zhao, Li, Wang, & Lv, 2012). Sensory analysis has been widely employed by the inspection services to evaluate freshness of fishery products (Calanche et al., 2013).

The fluorescence spectra recorded on the fluorophores give information about the environment of the fluorescent molecules as well as on the protein–protein, protein–water and/or protein– lipid interactions (Karoui, Schoonheydt, Decuypere, Nicolaï, & De Baerdemaeker, 2008). NADH, vitamin A, and proteins containing fluorescent amino acids such as tryptophan, tyrosine, and phenylalanine residues are the best-known fluorescent molecules in fish (Hassoun & Karoui, 2015a; Hassoun & Karoui, 2015b; Karoui, Kemps et al., 2006). 3.5.1.

Nonetheless, the high perishability of fish has also been well identified, being manifested in the form of various post mortem deterioration processes and resulting, essentially, in a short shelf-life of fresh fish even under conditions of storage in ice (Cakli et al., 2006(Cakli et al., 2007Carrascosa et al., 2016;Koutsoumanis, 2001;Koutsoumanis and Nychas, 2000;Parlapani et al., 2013Parlapani et al., , 2014.

Fish freshness has been regarded as one of the most important aspects of raw fish quality definition (Cakli et al., 2006;Hassoun and Karoui, 2017) and is affected and delineated by several factors. Examples of such factors are rigor mortis, autolysis processes and microbiological spoilage, with the latter playing a principal role in the highly perishable character of fish (Cheng et al., 2015b;Hassoun and Karoui, 2017).

Given the importance of microbiological spoilage in fish freshness deterioration, investigation of analytical approaches for its rapid and non-invasive assessment presents significant research interest. Several non-invasive/non-destructive techniques have been evaluated as propitious in fish quality assessment, including spectroscopic techniques and imaging technology approaches Sun, 2015, 2017;Cheng et al., 2015b;Hassoun and Karoui, 2017;Liu et al., 2013;Pérez-Esteve et al., 2014).

Fourier transform infrared (FTIR) spectroscopy is a biochemical fingerprinting technique which, in conjunction with multivariate data analysis, has shown significant potential in the detection and quantification of spoilage bacteria in muscle foods, including fresh meat and poultry and processed meat products (Argyri et al., 2013;Cheng and Sun, 2015;Moreirinha et al., 2015;Sahar and Dufour, 2014)

In the food industry, quality is frequently defined using terms related to nutrition, microbiology, physicochemical characteristics or consumer acceptability (Hassoun and Karoui, 2017). These terms should be analysed through an integrated vision since all of them contribute to quality assessment in different steps of the supply chain (Hassoun and Karoui, 2017).

To overcome such undefined terminology, Bremner proposed a hierarchial approach that encompasses all the aspects (concepts, criteria, specifications of the criteria and methods to provide values for the criteria) (Bremner, 2000)

Quality in fish products relates to attributes that fish possess, among distinct species, as well as in the same species. Such attributes vary due to interactions of endogenous factors (e.g.: age, proximate composition) as with environmental, nutritional and rearing conditions (Hassoun and Karoui, 2017;Matos et al., 2017).

The most common key attributes associated to consumer conception of food quality and their associated decisions, are related with organoleptic characteristics (e.g.: taste, odour, flavour); marketable traits (e.g.: freshness, size); safety (e.g.: parasites, hygiene) and nutritional value (e.g.: vitamins, fatty acids) (Matos et al).

Consumer needs for fresh fish and food security require market players to be able to maintain the freshness of the fish until it reaches consumers. Skipjack tuna is the same thing as other fresh fish which are easily damaged due to decay due to high water activity (aw), neutral pH, low connective tissue content, and the presence of autolytic enzymes [5].

Changes in the quality of fresh fish begin shortly after the fish is caught/harvested. The freshness of fish is a significant factor in seafood end products that are influenced by rigor mortise and post-death autolysis processes, which can accelerate the decline in fish quality [5] [6]. The rapid decline in the quality of fresh fish is also due to the handling and storage methods applied [7] [8].

1.2 Statement Of The Problem

Consumer needs for fresh fish and food security require market players to be able to maintain the freshness of the fish until it reaches consumers. Skipjack tuna is the same thing as other fresh fish which are easily damaged due to decay due to high water activity (aw), neutral pH, low connective tissue content, and the presence of autolytic enzymes[5].

Changes in the quality of fresh fish begin shortly after the fish is CAUGHT.

Most of the fish caught from the Cameroon waters is not sold in Cameroon, it is rather sold in other foreign countries and just very few is brought to the Cameroon’s landings.

Most of the fish consumed in Cameroon are imported from other countries at a cheaper price and these fish are preserved with very harmful chemicals such as formalin and other harmful chemicals used as preservatives to transport the fish. These chemicals when consumed alongside the fish, bioaccumulate and poses a serious health problem to consumers in the long-run. And also, most of these chemicals have carcinogenic effects on humans in the long run.

 

 

1.3 Objective of The Study

In this context, this study aimed to develop a sensory scheme based on the Quality Index Method (QIM) (sensory table and point system) for freshness monitorization and shelf-life prediction for aquatic products both the ones harvested from our Cameroon water, based on samples collected at the Batoke- ngeme beach, Down beach, Limbe and those suspected to be imported from abroad, based on samples collected from cold stores in Buea.

The main objective of the research work is for the classification and quality determination of the different aquatic products consumed in the south west Region of Cameroon, both those from our waters and the ones imported from abroad.

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