Abstract
The study aimed to analyze the possibility of waste frying oil utilization in home-made soap production. Soaps were made from unheated and fried rapeseed, sunflower and palm oils that had total polar material (TPM) values up to 24%. Physicochemical and microbial analyses were performed on produced samples to check their quality. The hardness increased with the degradation level of rapeseed and palm oils, and opposite findings were obtained for sunflower-made soaps. The highest malondialdehyde (MDA) contents were recorded for sunflower oil-made samples, with the maximum of 6.61 µg/g, and the lowest for the palm oil-made samples, with the maximum of 0.94 µg/g. The antimicrobial assessment showed no significant (p > 0.05) differences between control soap samples and soaps made of oils with the highest TPM value. Gram-positive bacteria (methicillin-resistant Staphylococcus aureus: MRSA) were the most sensitive chosen microorganisms, compared to Gram-negative bacteria and yeasts. The obtained results did not show exact differences between experimentally produced soap samples from fried or not fried oils; these findings highlight the potential of home-made soap production from this byproduct.
Highlights
The amount of waste is increasing together with the world’s population growth, meaning that reverse logistics systems have been gaining in importance [1,2]
The results for physicochemical analysis performed on soap samples are presented in Tables 2 and 3
Significant (p < 0.05) differences were obtained between the samples, but an unambiguous trend of difference between control samples (R0, S0 and P0) and samples made from the oil with the highest total polar material (TPM)% (R5, S5 and P5) was not observed
Summary
The amount of waste is increasing together with the world’s population growth, meaning that reverse logistics systems have been gaining in importance [1,2]. Waste frying oil represents one of the most important byproducts due to its hazardous impact on the environment [3]. 200 million tons of frying vegetable oils are being produced annually in the world with an increasing trend [5,6]. 1 L of waste oil poured into water can pollute up to 500,000 L of fresh water [3]. A larger portion of waste frying oil that comes from restaurants and industry is being collected and utilized. According to Greenea, in the European Union, 51% of frying oil waste comes from households and only a few percent is being collected [7]. A large amount of this waste ends up in sewage, causing environmental and economic problems
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