The researchers, who received no external funding for the study, examined whether essential oil extracted from Citrus sinensis orange peel waste could be used to formulate effective and consumer-accepted antibacterial hand gels.
In addition to laboratory testing, the study included a large-scale sensory evaluation to assess real-world user response.
Strong antibacterial performance from orange peel essential oil
The study authors reported that the essential oil extracted from orange peel waste showed high antibacterial activity in laboratory testing. Chemical analysis found that the oil contained 96.5% limonene, a compound widely used in fragrance and cleaning applications.
“The pure orange essential oil exhibited strong inhibition against Escherichia coli and Staphylococcus aureus, with inhibition zones of 25.9 mm and 23.62 mm, respectively,” the researchers wrote.
According to the study, this level of performance places the oil in the highest effectiveness category for citrus-derived essential oils. The authors noted that limonene was the primary driver of antibacterial activity, supported by smaller amounts of other naturally occurring compounds.
Formulated hand gels show lower efficacy but high usability
Researchers further examined how the essential oil performed once incorporated into finished hand gel formulations. Two alcohol-based gels containing 60% ethanol were developed and evaluated.
“Although the gels showed reduced antibacterial activity due to limited diffusion of active compounds in the gel matrix, they retained antiseptic properties suitable for topical use,” the researchers reported.
While the antibacterial effect was lower than that of the pure oil, the authors described this result as typical for gel-based systems.
Sensory testing highlights consumer preference
To assess how the gels would be received by consumers, the researchers conducted a sensory evaluation with 770 participants. The results showed strong overall acceptance, particularly for one formulation.
“GSA achieved 99% overall acceptability and superior scores in appearance, spreadability, absorption, and smell,” the researchers wrote.
Appearance and spreadability were the main factors separating the two prototypes, while color was not a meaningful differentiator. The study also found broad openness to switching away from conventional products.
“Overall, 93% of respondents are willing to use either GSA or GSB as a daily hygiene product over commercial ones,” the researchers reported.
Cost and sustainability considerations
In addition to performance and consumer response, the study addressed production economics. The researchers estimated that the gels could be produced for $1.27 to $1.45 per liter, which was noted to be well below typical commercial price ranges cited in the study.
“These results confirm that high-limonene orange peel essential oil can be effectively upcycled into sustainable, cost-competitive, and user-preferred alcohol-based hand sanitizers,” the researchers wrote.
Source: Cosmetics,2025, 12, 288. Doi: 10.3390/cosmetics12060288. “High-Limonene Orange Peel Essential Oil as a Natural Antibacterial Agent in Hand Sanitizer Gels.” Authors: Coronado, M.A., et al.
