Houcine Mhemdi

Oilseed treatment by ultrasounds and microwaves to improve oil yield and quality: An overview

Abstract Efficiency is a key point to ensure the profitability in the production of vegetable oils from oilseeds. To maximize the recovery yields of seed oils, the traditional process involves mechanical expression followed by subsequent chemical extraction using organic solvents (e.g. hexane). Besides health, environmental, and economic related issues to the use of organic solvents, thermal treatment of seeds during conventional oil extraction process inevitably leads to chemical changes (e.g. changes in macronutrients such as protein denaturation/degradation in the meal, oil oxidation, and changes in minor constituents such as fatty acids, sterols, phenolic compounds and tocols). Thus, at this stage of development there is a need for new efficient processes that can improve oil yield and its quality from an economical and environmental point of view. Several research groups have investigated the potential of ultrasounds (US) and microwaves (MW) as additional seed treatments to enhance oil yields and to reduce temperature and extraction times with promising results. The present review is devoted to critically discuss the main findings reported in the literature regarding the feasibility of using US and MW as potential tools to improve oil recovery yields as well as its nutritional, sensorial and physicochemical properties.

Seed oil polyphenols: rapid and sensitive extraction method and high resolution-mass spectrometry identification.

Phenolic content is a primary parameter for vegetables oil quality evaluation, and directly involved in the prevention of oxidation and oil preservation. Several methods have been reported in the literature for polyphenols extraction from seed oil but the approaches commonly used remain manually handled. In this work, we propose a rapid and sensitive method for seed oil polyphenols extraction and identification. For this purpose, polyphenols were extracted from Opuntia stricta Haw seed oil, using high frequency agitation, separated, and then identified using a liquid chromatography-high resolution mass spectrometry method. Our results showed good sensitivity and reproducibility of the developed methods.

Seed oil extraction from red prickly pear using hexane and supercritical CO2 : assessment of phenolic compound composition, antioxidant and antibacterial activities.

BACKGROUND Investigating Opuntia species for their seed oil content is of much importance owing to their potential use for food and in cosmetic applications. These oils have an important content in unsaturated fatty acids as well as antioxidant compounds (e.g. polyphenols, vitamin E), which have been associated with the prevention of some chronic diseases. Moreover, Opuntia stricta oils possess important antimicrobial activities. For instance, the main focus of this study was to compare the effectiveness of conventional (hexane extraction) and novel (supercritical (SC)-CO2 ) extraction methods for the recovery of oil and phenolic compounds from O. stricta seeds. The oil yield of both extracts was then compared and the polyphenol content and composition of both extracts were determined by liquid chromatography-high-resolution mass spectrometry. Additionally, antioxidant (DPPH assay) and antimicrobial activities (disc diffusion method) of O. stricta seed oils were determined. RESULTS The oil yield (based on Soxhlets method) of O. stricta seeds was determined using SC-CO2 (49.9 ± 2.2%), and hexane (49.0 ± 1.5%). Although obtaining similar oil extraction yields using the two methods, the extracted oil using SC-CO2 was more enriched in polyphenols (172.2 ± 11.9 µg gallic acid equivalents (GAE) g-1 oil) than that extracted using hexane (76.0 ± 6.9 µg GAE g-1 of oil). Polyphenol profiles showed that the SC-CO2 process led to the yield of more compounds (45) than that using hexane extraction (11). Moreover, the antioxidant and antimicrobial activities of SC-CO2 extract showed a high percentage of inhibition. CONCLUSION SC-CO2 extraction of O. stricta seed oil led to extraction of oil with a similar yield to that with hexane extraction, but with higher polyphenol content. The extract containing polyphenols exhibited high antioxidant and antibacterial properties, demonstrating their great potential as feedstock for high-oil quality.

Water-soluble polysaccharides from Opuntia stricta Haw. fruit peels: recovery, identification and evaluation of their antioxidant activities

Abstract Opuntia stricta Haw. is considered as one of the most common cactus plant growing in Tunisia. Extracting valuable compounds from its fruit peel, considered as by-product, is drawing more and more attention, making it on the verge of commercialization. Water-soluble polysaccharides were extracted from Opuntia stricta Haw. peels, and their chemical composition assessed using thin layer chromatography. The antioxidant activities of the extracted polysaccharides were assessed using 2,2-diphenyl-1-picrylhydrazyl free radical scavenging activity, total antioxidant activity and reducing power capacity. The extraction yield of water-soluble polysaccharides was 7.53±0.86%. The chemical composition revealed the presence of rhamnose, arabinose, glucose, mannose, galactose and galacturonic acid. The infra-red spectroscopic analysis showed a similar structure to that of Opuntia ficus-indica polysaccharide peels. Additionally, the extracted polysaccharides exhibited high antioxidant activities. In fact, the free radical scavenging activity (half inhibition concentration = 6.5 mg ml−1 with 94.9% inhibition at 50 mg ml−1), the total antioxidant activity (100 μg ascorbic acid equivalent at 50 mg polysaccharides) and the reducing power capacity (absorbance 700 nm = 0.7 at 50 mg ml−1), appeared to be interesting compared to natural and synthetic antioxidants. Therefore, water-soluble polysaccharides from Opuntia stricta Haw. fruit peels could be a natural alternative to replace synthetic antioxidants.