Investigation of Enzymatic Browning and Antioxidant Changes in Plantain (Musa spp.) During Ripening in Ondo State

Investigation of Enzymatic Browning and Antioxidant Changes in Plantain (Musa spp.) During Ripening in Ondo State

Abstract

Plantain (Musa spp.) is one of the most consumed staple fruits in Nigeria and plays a vital role in both nutrition and commerce. However, during ripening, it undergoes visible enzymatic browning and biochemical changes that affect its nutritional quality, antioxidant activity, and consumer acceptability. This study investigates the pattern of enzymatic browning and variations in antioxidant content during the ripening stages of plantain in Ondo State.

Freshly harvested unripe, semi-ripe, and fully ripe plantain samples were analyzed for polyphenol oxidase (PPO) and peroxidase (POD) activities, total phenolic content, vitamin C levels, and antioxidant capacity using spectrophotometric methods. The findings revealed that PPO and POD activities increased progressively with ripening, leading to enhanced browning intensity. Conversely, total phenolic and vitamin C contents declined steadily as ripening advanced, reducing the overall antioxidant potential of the fruit.

The results suggest that enzymatic browning during ripening is closely linked to oxidative degradation of antioxidants. Consequently, minimizing post-harvest storage time and applying antioxidant-preserving treatments could help maintain nutritional quality and market value. This study provides valuable biochemical insight into plantain post-harvest physiology and supports better handling practices for fruit preservation.

Keywords: Enzymatic Browning, Antioxidants, Polyphenol Oxidase, Ripening, Plantain, Ondo State

CHAPTER ONE

1.0 Introduction

Plantain (Musa spp.) is an important tropical fruit widely cultivated and consumed in Nigeria, particularly in Ondo State. It serves as a major source of carbohydrates, minerals, vitamins, and dietary fiber. During ripening, plantain undergoes several physical and biochemical transformations that influence its taste, texture, and color. One of the most prominent biochemical changes is enzymatic browning, a process that leads to the darkening of the fruit surface and pulp. This browning, although natural, often reduces consumer appeal and commercial value.

Enzymatic browning primarily results from the oxidation of phenolic compounds by enzymes such as polyphenol oxidase (PPO) and peroxidase (POD). These enzymes become more active as ripening progresses, especially under high oxygen and temperature conditions. At the same time, antioxidant compounds such as vitamin C and phenolics decline, reducing the fruit’s ability to neutralize free radicals. Understanding how these biochemical processes interact is essential for improving post-harvest management and maintaining fruit quality during storage and marketing.

1.1 Background of the Study

Plantain contributes significantly to the food security and economy of southern Nigeria. In Ondo State, it is a staple food consumed in various forms — boiled, roasted, or fried. However, due to its high moisture content, plantain deteriorates quickly after harvest. Ripening triggers a series of enzymatic reactions that alter its biochemical composition.

Among these reactions, enzymatic browning is particularly significant because it directly affects appearance and consumer preference. The enzymes responsible—PPO and POD—oxidize phenolic compounds to quinones, which polymerize to form brown pigments. In addition, oxidative stress increases during ripening as antioxidant enzymes and non-enzymatic antioxidants reduce in concentration.

Consequently, understanding these changes provides insight into fruit physiology and helps develop strategies to slow down undesirable browning reactions. Such knowledge benefits farmers, traders, and food processors who depend on plantain as a major income source.

1.2 Statement of the Problem

Despite the economic importance of plantain in Ondo State, post-harvest losses remain high due to rapid ripening and browning. Many local farmers and traders have limited knowledge of the biochemical processes behind these quality changes. Enzymatic browning not only reduces aesthetic appeal but also leads to nutrient loss. Similarly, the reduction of antioxidant compounds during ripening lowers the fruit’s nutritional value. Therefore, there is a need to investigate the relationship between enzymatic browning and antioxidant changes during ripening to support improved preservation techniques.

1.3 Aim and Objectives of the Study

Aim:
To investigate enzymatic browning and antioxidant changes in plantain (Musa spp.) during ripening in Ondo State.

Objectives:

1. To determine the activities of polyphenol oxidase (PPO) and peroxidase (POD) enzymes during different ripening stages.

2. To measure changes in total phenolic and vitamin C contents across ripening stages.

3. To evaluate the relationship between enzyme activity and antioxidant levels during ripening.

4. To recommend effective strategies for reducing browning and preserving antioxidant content in plantain.

1.4 Research Questions

1. How do PPO and POD activities vary during plantain ripening?

2. What changes occur in the antioxidant levels as the fruit ripens?

3. Is there a correlation between enzymatic browning intensity and antioxidant loss?

4. What post-harvest practices can help preserve the nutritional and visual quality of plantain?

1.5 Significance of the Study

This study provides biochemical evidence of how enzymatic and antioxidant systems interact during fruit ripening. The findings will help farmers, traders, and processors understand how to manage post-harvest losses effectively. Moreover, food scientists and nutritionists can apply the results to design methods that enhance shelf life and retain nutritional quality. By linking enzymatic browning to antioxidant depletion, this research offers practical insights for improving fruit preservation and consumer health in Ondo State.

1.6 Scope of the Study

The research focuses on locally cultivated plantain (Musa spp.) from selected farms and markets in Ondo State. It examines three major ripening stages: unripe (green), semi-ripe (yellow-green), and fully ripe (yellow). The study analyzes polyphenol oxidase and peroxidase activities, total phenolics, vitamin C levels, and antioxidant capacity. Other biochemical parameters such as sugar content or amino acid composition are beyond this study’s scope.

1.7 Definition of Terms

• Enzymatic Browning: A biochemical process where enzymes such as polyphenol oxidase oxidize phenolic compounds, resulting in brown pigments.

• Antioxidants: Compounds that prevent oxidative damage by neutralizing free radicals.

• Polyphenol Oxidase (PPO): An enzyme that catalyzes the oxidation of phenolics to quinones, initiating browning.

• Peroxidase (POD): An enzyme that assists in oxidative reactions using hydrogen peroxide as a substrate.

• Phenolic Compounds: Natural antioxidants found in fruits that contribute to flavor and color stability.

• Vitamin C (Ascorbic Acid): A potent antioxidant that protects against oxidative stress and enhances immune function.