Recovery of valuable compounds from palm-pressed fiber by using supercritical CO2 assisted by ethanol: modeling and optimization

Tailored recovery of antioxidant fractions enriched in caffeine and phenolic compounds from coffee pulp using ethanol-modified supercritical carbon dioxide

Coffee pulp (CP) is the by-product of coffee processing that urgently needs to be revalorized using sustainable technologies. This work applied a design of experiment (DoE) for modeling the extraction of bioactive compounds from CP using supercritical carbon dioxide (sc-CO2) with ethanol as a co-solvent under variable conditions (temperature, pressure, and ethanol percentage). Considering extraction efficiency (per unit of CP) and extraction selectivity (per unit of extract), results showed that ethanol percentage significantly enhanced the efficiency of total phenolic content, as well as the selectivity of chlorogenic acid and protocatechuic acid (p < 0.05). The effects of temperature and pressure in EtOH-modified sc-CO2 extraction exhibited non-linear patterns, highlighting the interaction between temperature and ethanol. Total phenolic content was responsible for the antioxidant activity of the EtOH-modified sc-CO2 extracts, which was also affected by caffeine in the extracts. The extraction condition that balances both efficiency and selectivity was found at 65 °C, 23 MPa, and 9 % ethanol as co-solvent. The extraction yield (5.8 mg/g CP) was 3.8 times and 6.7 times lower than that of aqueous and ethanolic extraction, respectively, indicating a relatively lower efficiency of sc-CO2. However, the selectivity of caffeine (106.3 mg/g extract) and sum of identified phenolic compounds (16.3 mg/g extract) such as chlorogenic, protocatechuic, and caffeic acids, especially for protocatechuic acid (14.9 mg/g extract), was superior to conventional extraction, resulting in the better ABTS chemical (182.3 mg TE/g extract) and cellular antioxidant (384.9 U/mg extract) activities. The notable enrichment of caffeine and protocatechuic acid, together with the antioxidant potential observed in the EtOH-modified sc-CO2 extracts of CP could be promising for functional food, cosmetic, and pharmaceutical industries.

Valorization of Peanut Skin as Agricultural Waste Using Various Extraction Methods: A Review

Peanuts (Arachis hypogea) can be made into various products, from oil to butter to roasted snack peanuts and candies, all from the kernels. However, the skin is usually thrown away, used as cheap animal feed, or as one of the ingredients in plant fertilizer due to its little value on the market. For the past ten years, studies have been conducted to determine the full extent of the skin's bioactive substance repertoire and its powerful antioxidant potential. Alternatively, researchers reported that peanut skin could be used and be profitable in a less-intensive extraction technique. Therefore, this review explores the conventional and green extraction of peanut oil, peanut production, peanut physicochemical characteristics, antioxidant activity, and the prospects of valorization of peanut skin. The significance of the valorization of peanut skin is that it contains high antioxidant capacity, catechin, epicatechin resveratrol, and procyanidins, which are also advantageous. It could be exploited in sustainable extraction, notably in the pharmaceutical industries.

Insight into Green Extraction for Roselle as a Source of Natural Red Pigments: A Review

Roselle (Hibiscus sabdariffa L.) is a source of anthocyanins as red pigments that is extensively farmed in tropical and subtropical regions, including Indonesia, Malaysia, China, Thailand, Egypt, Mexico, and West India. The roselle plant contains a variety of nutrients, including anthocyanins, organic acids, pectin, etc. Due to the toxicity and combustibility of the solvents, traditional extraction methods for these compounds are restricted. Obtaining pure extracts is typically a lengthy procedure requiring many processes. Supercritical carbon dioxide (ScCO₂) extraction as a green technology is rapidly improving and extending its application domains. The advantages of this method are zero waste production, quicker extraction times, and reduced solvent consumption. The ScCO₂ extraction of natural pigments has great promise in food, pharmaceuticals, cosmetics, and textiles, among other uses. The ScCO₂ technique for natural pigments may also be advantageous in a variety of other contexts. Due to their minimal environmental risk, the high-quality red pigments of roselle rich in anthocyanins extracted using ScCO₂ extraction have a high sustainability potential. Therefore, the objective of this review is to increase knowledge related to the natural colorant of roselle as a substitute for chemically manufactured colorants using ScCO₂ as a green method. This article covers ScCO₂ extraction, particularly as it relates to the optimization of pigments that promote health. This article focuses on the high extraction efficiency of ScCO₂ extraction. Natural colorants extracted via ScCO₂ are regarded as safe compounds, especially for human consumption, such as novel functional food additives and textile and pharmaceutical colors.

Effect of Overfilled Solvent and Storage Time of Subcritical Extraction of Jasminum sambac on Yield, Antioxidant Activity, Antimicrobial Activity and Tentative Volatile Compounds

Essential oil from Jasminum sambac flowers has demonstrated the potential of antioxidant and antimicrobial properties. However, jasmine flowers contain only a small amount of essential oil; therefore, subcritical fluid extraction (SFE) with HFC-134a, one of the effective extraction methods for flower extraction, was performed in this study. The percentage of overfilled solvent and storage time of the flowers were varied during the extraction. Antioxidant potential, antimicrobial potential and tentative volatile compounds were investigated in this study to observe the quality of the essential oil. It was discovered that a greater amount of overfilled solvent resulted in thicker essential oil and a longer storage time resulted in a lower amount of total oil yield. It could be seen that almost all extraction conditions did not have any significant difference in antioxidant and antimicrobial potential. The essential oil contained primary compounds such as indole, 9-tricosene, α-farnesene, muurolene, and benzyl alcohol. This study led to the conclusion that the amount of overfilled solvent from SFE affected the thickness of jasmine essential oil and its tentative volatile compounds. The longer storage time caused the significantly lower essential oil yield, but changing the extraction conditions had no significant effect on antioxidant or antimicrobial potential.