Rodriguez At His Best Rar Extractor
Leana Eckes
The by-products produced from fruit processing industries could be a potential hazard to environmental pollution. However, these by-products contain several biologically active molecules (essential fatty acid, phenolic compounds, flavonoids, coloring pigments, pectin, proteins, dietary fibers, and vitamins), which can be utilized for various applications in the food, pharmaceutical, cosmetic and textile industries. Nevertheless, during extraction, these bioactive compounds' recovery must be maximized using proper extraction technologies, keeping both economy and environment under consideration. In addition, the characteristics of the extract obtained from those by-products depend mainly on the parameters considered during the extraction process. In this review, an overview of different technologies used to extract bioactive compounds from fruit industry by-products such as seeds and peels has been briefly discussed, along with their mechanisms, process, advantages, disadvantages, and process parameters. In addition, the characteristics of the extracted bioactive compounds have also been briefly discussed in this review.
The by-products management of fruit and vegetable industries are becoming a universal concern. The problems can be lessened by applying the extraction conception which means the recovery of bioactive compounds, vitamins, fatty acids, minerals and polysaccharides from the bio-residues, such as seeds and peels. Several studies in the literature have reviewed the different extraction technologies for the valorization of waste. In addition, the technologies are compared with their acceptance of the industrial level. However, the review has also explored the different characterization processes of extracted bioactive compounds. Moreover, integration between two or more extraction technologies for the recovery of bioactive compounds have been enlightened in this review. Overall, this study describes the valorization of waste produced from industries by extracting bioactive compounds with help of different traditional and novel extraction technologies.
On the other hand, these by-products are an excellent source of bioactive compounds, such as phenolic compounds (phenolic acid, carotenoids, flavonoids), bioactive proteins (peptide isolate, amino acids), fatty acids, fibres, and so on. For instance, the seeds of fruits are a good source of essential oils, phytochemicals, and phytosterols. Similarly, the peels contain pectin, valuable fibers, and minerals (Marić et al. 2018; Mena-Garca et al. 2019). These bioactive compounds can be extracted from the by-products using different technologies and can be utilized to develop various valorized products, including functional foods or dietary supplements. In addition, in this way, the disposal of waste to the environment can be minimized.
The extraction technologies are categorized according to their extraction efficiency, cost-effectivity, and sustainability. Several extraction processes are followed for the recovery of bioactive compounds from the fruit industry by-products. These compounds can be separated, identified, and characterized to be utilized by different food, pharmaceutical, cosmetic or textile industries (Altemimi et al. 2017a; Marić et al. 2018). The bioactive compounds cause a lower risk of cancer, cataract, Alzheimer's, Parkinson's disease, ageing disorder, and heart-related diseases. Due to their high antioxidant activity and antimicrobial activity, these compounds perform defensive action toward chronic diseases, preventing the production of cancerous chemicals and balancing the immunosystem. These compounds are beneficial by being used as an additive in functional foods or consumed as a dietary supplement. Besides nutraceutical properties, natural antioxidants and colour compounds can be a better replacement for synthetic antioxidants, which could be used in different pharmaceutical and processing industries (Altemimi et al. 2017a; Azmir et al. 2013; Sasidharan et al. 2011). The processes starting from extraction to separation, isolation, identification, and characterization of fruit byproducts were summarized in the flow chart shown in Fig. 1. Thus, the extraction and valorization of bioactive compounds from fruit industry by-products improve societal health by providing nutritious food, mitigating the environmental problem, and reducing the waste disposal burden. It, therefore, helps the industries from an environmental and economic point of view (De Ancos et al. 2015; Kowalska et al. 2017; Trigo et al. 2020).
This review aims to provide an overview of the fruit industry by-products, a rich source of bioactive compounds. In addition, conventional (soxhlet, maceration, and hydrodistillation) and emerging (supercritical fluid, subcritical fluid, microwave-assisted, ultrasonic-assisted, enzyme-assisted, and pulsed electric field-assisted) techniques, along with separation, isolation, and identification by different analytical methods and quantification using various chromatographic and spectrophotometric methods. Furthermore, this review enlights on the mechanisms, advantages, and disadvantages of the above extraction techniques.
Different extraction technologies are utilized to extract beneficial compounds, especially bio-actives, present in the innermost portion of the cell of fruit by-products. A schematic diagram of available extraction technologies along with their mechanism of action is given in Fig. 2. The selection of technology for the extraction process is based on the required degree of purity of the extract, physical and chemical properties of the compound of interest, the location of the compound to be extracted (i.e., either it is free or it is bounded inside the cell of the by-products), cost-effectiveness and value of the extracted product. Before extraction processes, there are several unit operations to be done for better yield. Washing, cutting, size reduction, and drying are examples of various unit operations (Gong et al. 2020).
The standard conventional extraction techniques take a lot of time, energy, and solvent during processing and have some drawbacks. Due to this, emerging technologies are popularly used these days in pharmaceuticals, food, and medicinal industries. They require fewer solvents, less extraction time, and have more extraction efficiency than conventional technologies (Belwal et al. 2020). These technologies are selected based on their advantages, disadvantages, operation principles, and equipment types available for extraction. The operation parameters, advantages, and disadvantages of different extraction technologies are described in Table 1.
Mainly the extraction process has the following objectives: (a) to extract the targeted bioactive compounds from complex plant samples, (b) to increase the selectivity of analytical methods, (c) to increase the sensitivity of bioassay by increasing the concentration of targeted compounds, (d) to convert the bioactive compounds into a more suitable form for detection and separation, and (e) to provide a reproducible and robust method that is independent of variations in the sample matrix (Azmir et al. 2013). However, the basic mechanisms of all the solvent extraction processes are: (1) the solvent penetrates the solid matrix; (2) the compound of interest dissolves in the solvents; (3) the compounds diffused out of the solid matrix; (4) the extracted compounds are collected (Smith 2003).
The factors affecting the different extraction process is illustrated in Table 1. Besides those, the primary factors influencing extraction efficiency are the type of solvents used, extraction time, the particle size of the sample, temperature of extraction, and solid/solvent ratio (Garavand et al. 2019). The particle size must be small to penetrate the solvent inside the sample, and the temperature should be high for a higher yield. But too much high temperature can cause the loss of volatile compounds during the extraction process. Too much duration cannot affect the extraction, since the extraction process attains an equilibrium state after a specific time. The ratio between solid and solvent should be moderate; a too-high ratio might take more time for extraction (Zwingelstein et al. 2020).
Industrial scaling up of the extraction requires extensive consideration of both economy and productivity, while the lab-scale extractions require only a small amount of raw materials and solvent. Several factors are considered during the large-scale extraction process, such as instrumentation, type of process (batch or continuous), kinetics, economics, and energy consumption (Belwal et al. 2020; Chemat et al. 2012). There have been many investigations about scaling up the extraction processes. About 60% of industrial applications are done with SFE, while 15% and 14% of extraction are carried out with ultrasound and microwave, respectively (Belwal et al. 2020; Chemat et al. 2019). In the case of the UAE, both probe and bath systems are used on pilot / industrial scales, and microwave reactors are usually preferred in industrial proposed extraction. Meanwhile, UAE is the primarily used extraction process for industrial-based juice production. However, in the case of PEF-assisted extraction process, there are still challenges for the industrial scaling up of the process.
Anthocyanins are water-soluble plant pigments of red, purple, and blue colour, derived from the peel of fruits, such as pear, watermelon, and apple. Similarly, carotenoids are another water-insoluble/ Lipid soluble plant antioxidants that are the precursors of vitamin A. Carotene (lycopene, β-carotene, α-carotene), xanthophyll (lutein) are some examples of carotenoids present in seeds and peels of the fruit. The arrangement of conjugated double bonds is responsible for the antioxidant activity of the carotenoids (De Ancos et al. 2015). Vitamins present in fruits and vegetables are responsible for preventing lipid oxidation, decreasing DNA damage, and maintaining immune function. Ascorbic acid and tocopherols are precursors of vitamin C and vitamin E, respectively. α, β, γ, δ tocopherols are four analogues that are responsible for hypolipidemic, antiatherogenic, antihypertensive, allergic dermatitis suppressive, neuroprotective, and anti-inflammatory activities (Golkar and Moattar 2019). The polysaccharides present in the cells of fruit by-products are responsible for the antihyperlipidemic, prebiotic, antitumor activities, and jellification and emulsification efficiencies. The polysaccharides are classified into water-soluble (pectin) and water-insoluble (cellulose, lignin) groups. Pectin is a heterogeneous type of acidic polysaccharides present in the cell lamella of fruits. Besides these, the oils extracted from the seed or peel powder, described in Table 2, have antioxidant, anticancerous, and antidiabetic properties because of the presence of fatty acids, such as polyunsaturated (linoleic acid, linolenic acid), and monounsaturated (oleic acid) (Golkar and Moattar 2019; Minh et al. 2019; Peso-Echarri et al. 2015; Yalcin and apar 2017).
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