Development and characterization of biodegradable packaging films from avocado seed starch by incorporating aloe vera gel

In the modern world, the plastic wrapper that keeps a sandwich fresh or a fruit crisp is a marvel of convenience, yet it carries a heavy environmental cost. Most of these wrappers are made from synthetic polymers, materials derived from petroleum that do not easily break down, accumulating in landfills and oceans for centuries. In response, scientists are turning to nature to find alternatives that perform the same protective job but can return to the earth. The core idea behind this shift is to use starch, a natural carbohydrate found in plants, as the main building block for packaging. Starch is abundant and biodegradable, meaning microorganisms in the soil can consume it and turn it back into harmless natural components. However, pure starch films often have weaknesses: they can be too brittle, dissolve too quickly when wet, or lack the strength to hold heavy items. To fix these flaws, researchers often mix in other natural substances that can strengthen the material or add useful properties, such as the ability to fight off bacteria that cause food to rot.

A researcher at Ambo University in Ethiopia set out to create a new type of biodegradable film by combining two specific natural ingredients: starch extracted from avocado seeds and gel from the aloe vera plant. Avocado seeds are a common waste product of the fruit processing industry, often discarded after the fruit is eaten or processed for oil. By extracting the starch from these seeds, the researcher aimed to turn a waste product into a valuable resource. They mixed this starch with aloe vera gel, a substance known for its soothing and preservative qualities, to see if the combination could create a packaging film that was strong, resistant to water, and capable of keeping food fresh. The goal was not just to make a film that falls apart, but one that offers real protection while remaining safe for the environment.

The researcher began by collecting raw materials, washing avocado seeds and aloe vera leaves, and processing them into a fine starch powder and a clear gel. They then created a series of test films by mixing different amounts of the starch and the gel with water and a small amount of glycerol, a substance used to keep the film flexible. They tested nine different combinations, varying the starch from 2% to 6% and the aloe vera gel from 0.5% to 1.5%. After heating and stirring the mixtures to create a smooth liquid, they poured them into dishes and dried them in an oven to form thin, transparent sheets. Once the films were ready, the researcher put them through a battery of tests to see how they held up under pressure, how they reacted to water, and whether they could stop bacteria from growing.

The results showed that the composition of the film mattered greatly. When the researcher increased the amount of avocado seed starch in the mixture, the film became significantly stronger. The strongest films, made with 6% starch, could withstand a pulling force of 10 megapascals, a measure of strength that was much higher than films made with less starch. This suggests that the starch granules formed a tight, interconnected network that could resist breaking. However, adding more aloe vera gel did not always make the film stronger; in fact, at higher concentrations, the gel seemed to weaken the structure slightly, likely because the extra moisture and gel components disrupted the tight bonding of the starch chains. Despite this, the addition of aloe vera did improve the film's ability to resist water vapor. The films with more aloe vera gel allowed less moisture to pass through them, which is a crucial trait for packaging that needs to keep food from drying out or getting soggy.

Beyond strength and water resistance, the films showed impressive abilities to fight bacteria. The researcher tested the films against two common types of bacteria: E. coli, which is often found in contaminated food, and Staphylococcus aureus, a bacteria that can cause skin and respiratory infections. When they placed small discs of the film on a culture of these bacteria, the bacteria stopped growing in a circle around the film. The size of this clear zone, where no bacteria could survive, ranged from 12 to 18 millimeters for E. coli and 14 to 20 millimeters for S. aureus. The films containing higher amounts of aloe vera gel performed the best, with some matching the effectiveness of a standard antibiotic used as a control in the experiment. This indicates that the aloe vera gel retained its natural antimicrobial properties even after being mixed into the film, offering a built-in shield against spoilage.

Perhaps most importantly for the environment, the films proved to be highly biodegradable. The researcher buried small pieces of the films in soil and weighed them every few days to see how much of the material disappeared over time. Within 25 days, the films had lost a significant portion of their weight, with some combinations breaking down by more than 80%. The film made with 4% starch and 1.5% aloe vera gel showed the highest rate of degradation, losing 81.5% of its weight in that period. This rapid breakdown suggests that once the packaging is discarded, it will not linger in the environment for decades but will instead be consumed by soil microbes and return to the earth.

The study concludes that it is entirely possible to transform avocado seed waste into a functional, eco-friendly packaging material by blending it with aloe vera gel. The resulting films are strong enough to handle the rigors of transport, effective at blocking moisture, and capable of inhibiting the growth of harmful bacteria. While the researcher noted that the exact balance of ingredients is critical—too much gel can weaken the film, while too little might not provide enough antimicrobial protection—the findings offer a promising path forward. By using agricultural byproducts that would otherwise be thrown away, this approach addresses both the problem of plastic pollution and the need for sustainable food packaging, turning a simple seed into a solution for a cleaner future.