University of Johannesburg study investigates potential of South African plant for fruit preservation

Professor Fawole, who serves as the chairperson of SARChI for Sustainable Preservation and Agroprocessing Research (SPAR) and director of the Postharvest Processing and Agroprocessing Research Centre (PARC) in the Department of Botany and Biotechnology at UJ, emphasizes the existence of health issues requiring further study. For instance, European experts have concluded that the widely used chemical fludioxonil violates criteria related to human hormonal system impact. In Professor Fawole's view, the fresh produce industry needs safer and more effective solutions that allow for reduced chemical dependency, manage resistance, and help exporters meet changing market demands.

Selection and Development of Base

One way to develop new solutions is by using essential oils from plants. This is where the local South African plant entered the study. Helichrysum splendidum was chosen because its essential oil demonstrated promising antifungal and antioxidant properties in early stages of research when tested against pathogens isolated from selected fruit crops. The plant is also noted for its resilience and fast growth, which could support sustainable production.

Fawole reported that they are collaborating with a company in the Western Cape that produces essential oils from local plants on an industrial scale, ensuring a reliable and stable supply, which increases the chances of commercial implementation. However, this essential oil has inherent problems: it evaporates easily, loses effectiveness during storage, and mixes poorly with water. Moreover, most people find the taste and smell too strong when using sufficient amounts to maintain the freshness of fruits and vegetables.

Encapsulation Technology

To solve the problems of odor, taste, and other difficulties, researchers applied a method known as 'encapsulation'. Encapsulation makes the oil easier to handle and increases its stability. As Mr. Yusuf Mukaila, a postgraduate student at SPAR and PARC, explains, encapsulation is similar to turning liquid milk into dry milk powder for coffee, where the liquid is converted into a dry form that is easier to store, transport, and mix when needed.

Mukaila added that the support structure in their powder is formed from chitosan and whey protein. This structure protects the oil droplets within the powder particles from evaporation or degradation and facilitates the mixing of the powder with water. The next step was determining the optimal 'recipe' for encapsulation, which needed to protect the essential oil droplets from evaporation and ensure slow but constant release of the oil to protect fresh fruits from spoilage. These tests were conducted exclusively under controlled laboratory conditions, and the recipes have not yet been tested on fruits.

Testing and AI Training

Instead, researchers tested against the fungus Penicillium digitatum, which causes green mold—a serious post-harvest disease of citrus. Mukaila noted that this fungus served as a useful proxy for one cause of fruit spoilage, but not for the entire fruit. The next step will be testing the best formulation on actual produce. However, these Petri dish experiments allowed for the comparison of each powder 'recipe' under identical conditions and yielded clean, reliable data for machine learning models (AI). To obtain sufficient data volume for training and testing AI models, postdoctoral researcher Dr. Kabiru Jimo created 20 different encapsulation 'recipes'. Each recipe contained a different ratio of essential oil, chitosan, and whey powder. Each recipe was tested three times simultaneously against Penicillium digitatum in Petri dishes. Researchers used the test results to train the AI model on ingredient interaction. Subsequently, one AI model was able to predict the optimal 'recipe' with the highest potential for preserving fresh fruits. Ultimately, they tested the 'AI-suggested optimal recipe' and found that the AI's predictions were more than 94% accurate.

Future Research Plans

Professor Fawole stated that in the next phase, researchers will conduct trials of the optimized AI powder on real fruits under realistic storage and transportation conditions. They will assess the degree of decay, weight loss, firmness, color, taste, and odor to determine if the powder can extend shelf life without compromising fruit quality.