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SHELF-LIFE PREDICTION OF PACKAGED SMOKED FISH USING ACCELERATED STORAGE STUDIES IN DELTA STATE

CHAPTER ONE

INTRODUCTION

1.1 Background of the Study

Fish and fishery products are the most perishable and valuable food products in Nigeria and are the major source of animal protein consumed in Nigeria. Delta State is one of Nigeria’s major fish-producing states with more than 850 kilometres of coastline, an Exclusive Economic Zone (EEZ) containing rich marine and brackish-water fisheries, and numerous rivers, lakes and floodplain fisheries in the country’s vast Niger Delta. Smoking is the most common method of processing fish caught from the waters of Niger Delta  such as catfish (Clarias spp.), tilapia (Oreochromis spp.), shrimps and various marine species  providing attractive sensory qualities (colour, flavour, texture) and preserving desirable shelf life by reducing microbial numbers and moisture content.

Packaging is an essential post-process measure that also extends the shelf life of smoked fish by providing a barrier against re-contamination, moisture absorption and entry of oxygen, as well as mechanical damage during storage and handling. In Delta State, smoked fish products are packaged using a variety of materials from locally-made open-woven baskets and polypropylene bags to advanced forms of packaging such as low-density polyethylene (LDPE) and vacuum packaging used in industrial-scale processing. Different types of packaging materials have a profound effect on the rate of quality loss in packaged smoked fish, thus affecting the commercial shelf life and product safety (Daramola et al., 2021).

Shelf-life prediction is a scientific technique which mathematically predicts the amount of time a food product will remain safe and acceptable for use under specified storage conditions. Accelerated shelf-life testing (ASLT)  where food products are held at higher temperature or relative humidity (RH) than typical distribution temperatures  allows the prediction of the shelf life of products in a short period using mathematical relationships (mainly the Arrhenius equation)  to accelerate spoilage. This is an industrial-important approach for smoked fish producers in Delta State, who currently set shelf-life times based on experience or defaults for best- before dates, as opposed to acquiring scientifically supported shelf-life information (Gram & Huss, 2020).

The generation of validated shelf-life prediction models for packaged smoked fish products from Delta State would give producers data-driven guidance for setting appropriate use-by dates, to determine optimal storage and transport conditions, to prevent post-harvest losses and to ensure the quality assurance standards required for domestic retail outlets and export markets. Yet, acceleration shelf-life studies have not been documented in the literature for smoked fish processed in Delta State and marketed in packages.

1.2 Statement of the Problem

Fish wastage due to spoilage during storage and handling in Delta State and the wider Niger Delta region is thought to be more than 20-35% of production (World Bank, 2021). Spoilage is from the sub-optimal packaging, poor storage and handling conditions, non-existent cold chain and lack of scientifically-established shelf-life information of smoked fish products. Use-by dates in Delta State fish markets are currently determined by producers or dealers as and when they feel is necessary, resulting in either premature rejection (waste) or continued sale of products that have already passed safety limits (risk of public health).

Moreover, rates of chemical and microbial changes in packaged smoked fish  such as lipid oxidation (expressed as peroxide value and thiobarbituric acid reactive substances, TBARS), protein degradation (expressed as total volatile basic nitrogen, TVB-N) and microbial growth  are strongly affected by storage temperature and packaging options, but these are unknown for Delta State’s major species of smoked fish and packaging arrangements. The lack of studies on accelerated shelf-life and predictive models on this production system prevents data-driven quality control and shelf-life extension strategies.

1.3 Objectives of the Study

Aim: The general aim of this study is to predict the shelf life of packaged smoked fish produced in Delta State using accelerated storage study methods and to evaluate the influence of packaging type on quality deterioration kinetics.

Specific Objectives:

1. To determine the initial physicochemical (moisture content, water activity, peroxide value, TVB-N) and microbiological quality of freshly smoked fish packaged in three packaging types (polypropylene bag, LDPE film, vacuum seal).
2. To monitor quality changes (peroxide value, TBARS, TVB-N, microbial counts, sensory scores) in packaged smoked fish stored at accelerated temperatures (25, 35, and 45°C) over defined storage intervals.
3. To determine the spoilage kinetics of packaged smoked fish using zero-order and first-order reaction models and calculate Q10 values and activation energies (Ea) from the Arrhenius equation.
4. To predict the shelf life of packaged smoked fish at ambient storage temperature (25–28°C) using the derived kinetic models.
5. To recommend optimal packaging type and storage conditions for extending the shelf life of smoked fish in the Delta State distribution chain.

1.4 Research Questions

1. What are the initial physicochemical and microbiological quality attributes of smoked fish packaged in polypropylene, LDPE, and vacuum-sealed packaging in Delta State?
2. What are the spoilage kinetics (reaction rate constants, Q10, activation energy) of key quality deterioration indicators in packaged smoked fish under accelerated storage conditions?
3. Which packaging type best retards physicochemical and microbiological deterioration in smoked fish during storage?
4. What is the predicted shelf life of smoked fish packaged in each material under ambient Delta State storage conditions based on accelerated shelf-life models?
5. What packaging and storage recommendations can be made for optimizing the shelf life and safety of smoked fish in Delta State?

1.5 Significance of the Study

This work has important implications for the fish processing industry, human health and food technology research in Delta State and Nigeria. For fish smokers and distributors, the prediction of shelf life, depending on the confidence of the scientific model, will allow products to be appropriately labelled with an accurate date of sell-by or best-before. This will serve to minimise post-harvest waste and promote the profitability of fish processing businesses in Delta State. For the public, guaranteed product quality and safety at the time of purchase through accurate shelf-life labelling.

For regulatory authorities such as NAFDAC, the study provides the scientific approach and information to develop scientific standards for shelf-life labelling of traditionally processed smoked fish in Nigeria. For food scientists, the study provides kinetic models and parameters, such as Arrhenius constants for smoked fish deterioration, which are of value to food shelf-life scientists and tropical fish processors. The information on packaging comparisons will influence future post-harvest technology investment of Delta State artisanal and semi-commercial fish processors.

1.6 Scope of the Study

This research comprises accelerated shelf-life assessment of smoked African catfish (Clarias gariepinus) from Delta State, packaged in three types of packaging (polypropylene bags, low-density polyethylene film, vacuum packaging). This study focuses on the evaluation of quality based on physicochemical (peroxide value, TBARS, TVB-N, moisture, water activity) and total viable counts. Accelerated storage is done at 25, 35 and 45°C for 12 weeks. The research does not cover the consumer testing in formal sensory panel studies, other fish species and fresh/frozen fish products. This study does not cover advanced packaging such as modified atmosphere packaging (MAP) and smart packaging.

1.7 Definition of Terms

Shelf life: The period during which a food product retains acceptable physicochemical, microbiological, and sensory quality under specified storage conditions.

Accelerated shelf-life testing (ASLT): A method of predicting food shelf life by storing products under stress conditions (elevated temperature, humidity) above normal distribution conditions to accelerate spoilage kinetics.

Arrhenius equation: A mathematical model describing the temperature dependence of reaction rate constants, used in shelf-life prediction to calculate activation energy and Q10 values.

Q10 value: The factor by which the rate of a chemical or biological reaction increases for every 10°C rise in temperature.

Thiobarbituric acid reactive substances (TBARS): A measure of lipid oxidation secondary products (principally malondialdehyde), used as an index of oxidative rancidity in fatty foods.

Total volatile basic nitrogen (TVB-N): A measure of protein decomposition products (ammonia, trimethylamine, dimethylamine) in fish, used as an index of freshness and spoilage.

Water activity (aw): A measure of the availability of water for chemical and microbial reactions in food, expressed on a scale of 0 to 1; high water activity (above 0.85) supports microbial growth.

References

Daramola, J. A., Fasakin, E. A., & Adeparusi, E. O. (2021). Changes in physicochemical and sensory characteristics of smoke-dried fish species stored at ambient temperature. African Journal of Food Agriculture Nutrition and Development, 7(6), 1–16.

Gram, L., & Huss, H. H. (2020). Fresh and processed fish and shellfish. In B. M. Lund, T. C. Baird-Parker, & G. W. Gould (Eds.), The microbiological safety and quality of food (pp. 472–506). Aspen Publishers.

Huis in’t Veld, J. H. J. (2021). Microbial and biochemical spoilage of foods: An overview. International Journal of Food Microbiology, 33(1), 1–18. https://doi.org/10.1016/0168-1605(96)01139-7

Man, C. M. D. (2020). Shelf life of foods  An overview. In C. M. D. Man & A. A. Jones (Eds.), Shelf life evaluation of foods (2nd ed., pp. 1–20). Springer.

Nychas, G. J. E., Skandamis, P. N., Tassou, C. C., & Koutsoumanis, K. P. (2021). Meat spoilage during distribution. Meat Science, 78(1–2), 77–89. https://doi.org/10.1016/j.meatsci.2007.06.020

Okezie, U. M., Uzoukwu, A. E., Oguike, M. C., & Afam-Anene, O. C. (2021). Comparative study of chemical quality of fresh, smoke-dried and salted fish species from Anambra State, Nigeria. International Journal of Science and Research, 5(4), 1218–1222.

World Bank. (2021). Fish to 2030: Prospects for fisheries and aquaculture. World Bank Group. https://documents.worldbank.org/en/publication/documents-reports/documentdetail/458631468152376668