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High Value-Added Compounds from Food Waste
High Value-Added Compounds from Food Waste Charis M Galanakis, Galanakis Laboratories, Chania, Greece Ó 2016 Elsevier Inc. All rights reserved.
Introduction Food Waste Sources and Value-Added Compounds Applications Vegetable and Plant By-products Olive By-products Coffee By-products Dairy By-products Animal By-products Fishery By-products The 5-Stage Universal Recovery Process Potential Use of Emerging Technologies The Universal Recovery Strategy Implementation of the Strategy to Develop Industrially Viable Products Further Reading
1 1 3 3 3 3 3 4 4 4 6 6 7 7
Introduction Until the end of the twentieth century, disposal of food waste was not considered as a matter of concern. Particularly, increase of food production without improving the efficiency of the food systems was the prevalent policy. This consideration increased generation of wasted food along supply chains. In the twenty-first century, escalating demands for processed foods have required identification of concrete directions to minimize energy demands and economic costs as well as reduce food waste. The perpetual disposal of high value-added materials in the environment is a practice that could not be continuing for a long time within the sustainability and bioeconomy frame of the modern food industry. The depletion of food sources, the fast-growing population, and the increasing need for nutritionally proper diets do not allow considering other alternatives. Up to the very recent years, the main methodologies for waste minimization and valorization included general methods such as incineration, anaerobic fermentation, biofuel conversion methods, composting and vermicomposting, landfill, or agricultural applications like animal feed and fertilizers. Subsequently, the potential of food waste to create new opportunities and markets was underestimated. Nowadays, consumers’ consciousness about environmental issues and legislative pressures increase the requirements of new management methods and treatments that focus on the recovery of value-added components from food waste and their reutilization in foodstuff. The recovered components typically improve targeted aspects of the final product quality. Value-added properties can be related to the shelf life or color of the final product, health benefits, formulation, or other product feature. Regardless of the branch of the food industry under investigation, waste streams are generated across various stages of the supply chain. For nutraceutical applications or conversion of by-products into chemicals, valuable components should be extracted from the matrix in appropriate way. Processing by-products of food and agricultural industry is of particular interest because of their abundance and existence in concentrated locations. Depending on the source (excluding meat and fish), these can be less susceptible to deterioration compared to the wastes produced at the end of food supply chain. Waste produced at the end of the chain tends to be highly dispersed (e.g., in individual households). This fact complicates their valorization as sources for value-added components recovery due to the need for an additional collection step and the reduced biological stability due to microbial growth. Due to regulatory and technical reasons, such as traceability and health and safety issues, by-products with a high potential for valorization are fruit- and vegetable-derived waste.
Food Waste Sources and Value-Added Compounds Food waste is composed of complex ingredients that have been discharged from the original sources. The waste streams that are originated by various branches of the food industry can be divided in two main groups (plant or animal origin) and seven subcategories (Table 1). Wheat grinding and rice dehulling produce bran and straw that are rich in high nutritional proteins and glucuronoarabinoxylans. Oat-processing waste has been proposed for the extraction of dietary fiber and particularly b-glucan. Potato processing during chips or french fries production generates phenol-rich solid wastes (e.g., peels or cull potatoes). Cassava peel has been proposed as a substrate for microbial protein enrichment. Sunflower and soybean seeds have been used to extract phytosterols. Besides, due to their high protein content, pulses processing by-products could be used in meat
Reference Module in Food Sciences
http://dx.doi.org/10.1016/B978-0-08-100596-5.03510-1
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High Value-Added Compounds from Food Waste
Table 1
Food wastes origin, sources, and respective high value-added compounds for recovery
Waste origin
Selected sources
Target ingredients
Plant 1. Cereals
Rice bran
Albumin and globulin Hemicellulose B and insoluble dietary fiber Arabinoxylans Hemicellulose Glucuronoarabinoxylans b-Glucan Glucose, arabinose, and galactose Arabinoxylans Phenols Organic acids Phytosterols Phytosterols Phytosterols Albumin Phenols Phenols and pectin Narirutin Hesperidin Apocarotenoid Limonene Pectin Pectin Phenols Pectin Protein Dietary fiber Phenols Calcium tartrate Enocyanin Cyanidin-3-rutinoside Soluble and insoluble dietary fiber b-carotene Phenols Lycopene Carotenoids Pectin
2. Roots and tubers 3. Oilcrops and pulses
4. Fruits and vegetables
Wheat middling Wheat straw Wheat bran Oat mill waste Malt dust Brewery’s spent grains Potato peel Sugar beet molasses Sunflower seed Soybean seed Soybean oil waste Soybean wastewater Olive pomace Olive mill wastewater Cold hardy mandarin peel Orange peel
Lemon by-product Apple pomace Apple skin Peach pomace Apricot kernel Grape pomace Grape skin Wine lees Banana peel Rejected and processed kiwifruits Carrot peel Tomato pomace Tomato skin Cauliflower floret and curd Animal 5. Meat products
6. Fish and seafood
Chicken by-products Slaughterhouse by-products Bovine blood Beef lung Sheep visceral mass Fish leftovers (skin, head, and bones)
7. Dairy products
Shrimp and crab shells Surimi wastewater Cheese whey
Proteins Proteins Proteins Protein concentrates Protein hydrolysates Proteins Lipids Chitosan/Chitin Proteins Lactose b-Lactoglobulin a-Lactalbumin
Adapted from Galanakis, C.M., 2012. Recovery of high added-value components from food wastes: conventional, emerging technologies and commercialized applications. Trends Food Sci. Technol. 26, 68–87.
and pasta production, ready-to-eat breakfast cereals, baby food, snack food, texturized vegetable protein, pet foods, dried soups, and dry beverages. Animal, fish, and seafood processing by-products (e.g., bones, tendons, skin, head, beef lung, or sheep visceral mass) contain high amount of proteins and lipids. Value-added compounds recovered from food waste are used today as additives in foodstuff due to their ability to provide advanced technological properties and health claims, respectively, to the final product.
High Value-Added Compounds from Food Waste
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Applications Vegetable and Plant By-products Most fruit (e.g., apple) and vegetable (e.g., carrot) by-products are rich sources of dietary fiber and natural antioxidants. Water-insoluble fiber (e.g., hemicelluloses) is able to improve intestinal regulation and thereby is destined to supplement food products or ready meals. Soluble dietary fiber (e.g., pectin) is known for its ability to lower blood lipid level and at the same time possesses advanced gelling properties that allow its application as thickener, emulsion stabilizer, and fat replacement in foods. Pectin is known to possess a variety of pharmacological activities such as antimetastasis and antiulcer activities. Besides, a regular generous intake of dietary fiber reduces risk for developing coronary heart disease, stroke, hypertension, diabetes, obesity, and certain gastrointestinal diseases. Natural antioxidants (e.g., phenols, carotenoids, tocopherols, and ascorbic acid) have been connected to both nutritional (reduction of oxidative stress, prevention of cancer, arteriosclerosis, ageing processes) and functional properties like natural food and beverage preservatives since they extend the shelf life of the product by delaying the formation of off-flavors and rancidity. Industrial commercialization of citrus peel is conducted for more than 30 years, whereas the recovered ‘sugar syrup’ contains essential oils, flavonoids (e.g., narirutin, hesperidin, etc.), carotenoids, sugar, and pectin. The latter product is used as a sweetener and flavor substance in juices, replacing artificial compounds, such as saccharine or aspartame. Due to the high concentrations of biologically active secondary metabolites remaining in citrus peel molasses, this raw material is also suitable as a source for functional food and/or food supplement ingredients. The industrial recovery of water-insoluble carotenoids (e.g., lycopene) from food wastes is under progress. Carotenoids act in prevention of cardiovascular diseases and specific cancers, whereas they are important dietary sources of vitamin A. Indeed, lycopene is one of the most popular natural pigments (red). Recently, the Food and Drug Administration (FDA) approved the use of higher levels of tomato lycopene to color processed meats, as alternative to carmine. Moreover, Food Safety and Inspection Service has established that tomato lycopene extracts and concentrates (GRN 000156) of 50 and 100 mg kg 1, respectively, could be used as coloring agent in ready-to-eat meat, poultry, and egg products.
Olive By-products At least five companies around the world recover phenols and particularly hydroxytyrosol from olive mill wastewater and sell them as natural preservatives, life-prolonging agents, or bioactive additives in vegetable oils, chocolates, bakery, meat products, and cosmetics. Hidrox is a commercially available product from CreAgri (Hayward, USA) with a high content of hydroxytyrosol and several beneficial (e.g., anti-inflammatory and antimicrobial) properties. Other relevant phenol-rich products include Olivactiv (Glanbia, Milan, Italy), Oleaselect, Opextan (Indena, Milan, Italy), Olive Braun Standard 500 from Naturex, olive polyphenols from Albert Isliker, Prolivols from Seppic Inc., Olive Polyphenols NLT from Lalilab Inc., Phenolea Complex Plus from PhenoPharm, and Lundolive P1100 from Phenoliv AB. Olive pulp extracts (in general) have been approved by FDA with GRAS status (GRN No. 459) for being used as an antioxidant in baked goods, beverages, cereals, sauces and dressings, seasonings, snacks, and functional foods at a level up to 3000 mg kg 1 in the final food. Besides, pectin derived from olive mill wastewater has been proved to restrict oil uptake of low-fat meatballs during deep fat frying.
Coffee By-products Coffee silverskin contains several bioactive compounds such as prebiotic carbohydrates, dietary fiber, and antioxidants. In agreement, patented extracts recovered from coffee silverskin contain high amounts of chlorogenic acid and caffeine, whereas their antioxidant activity survives the in vitro gastrointestinal digestion process and remain bioaccessible. Therefore, they have been proposed as an antioxidant additive in food and cosmetics manufacture, with potential excipient (preservative, flavoring) functions as well as antioxidant, anti-ageing, and anticellulite activities. Spent coffee grounds have been employed for the inventions of foods and beverages containing mannooligosaccharides, ultimately to reduce blood pressure, elevate suppressing effect, and reduce abdominal fat. They have also been used as ingredients in bakery products, pastry, confectionery, biscuits, and breakfast cereals. Finally, a gluten-free product has been recovered (Coffee flour) from coffee cherry (the surrounding pulp) and commercialized as additive in breads, cookies, muffins, squares, brownies, pastas, sauces, and beverages.
Dairy By-products Direct application of whey implies its utilization as a water replacer without any changes in its composition. This is the case of soft whey-based beverages production, wherein native sweet, diluted, or acid whey is mixed with different additives. Whey is also used to produce beverages obtained by fermentation with probiotic bacteria. On the other hand, dried whey powder could be utilized by dairy, baking, confectionary, baby food, and meat industry. The main target compounds of cheese whey for recovery purposes include casein fines, protein concentrates and lactose that are used as fat replacers, flavor enhancers, stabilizers, and nutritional supplements in foods, beverages, and confectionary. Whey proteins are characterized by their exceptionally high nutritional quality, predominantly determined by amino acid composition and physiological functionality. They possess also unique physical functional properties such as gelling, foaming, water binding, and emulsifying capacity. Hydrolyzed whey
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High Value-Added Compounds from Food Waste
proteins are known for their ability to reduce total and LDL cholesterol levels in mammals and thus could be used for the production of functional foods. APS BioGroup produces several commercial products from whey, such as colostrum and ImmuloxÒ powders, with immune system balancing effects and high level of proline-rich peptides. Ultimately, crude whey lactose is used as aroma stabilizer and sweetener.
Animal By-products Waste skimming sludge has typically an important nutritional value for feed applications, whereas chicken feathers have been used as a source of keratin for packaging uses. Collagen and gelatin from pig, ducks, and bovine skins can be recovered and used as a source of bioactive peptides after enzymatic treatment. Collagen can be used in gene transferring, by subcutaneous collagenous pellets for somatic gene therapy or for probiotic bacteria microencapsulation by spray-drying technology. Blood is a by-product of the meat industry with high content of good-quality proteins. Whole proteins (as albumin, fibrinogen, and globulins) can be separated from plasma. They have relevant functional properties like gelation, foaming, emulsifying, or thickening, which allow them to be utilized in the food industry as dietary supplements. More recent applications of blood proteins include the development of products with enhanced functional properties such as antioxidant, antimicrobial, mineral-binding, antigenotoxic, opioid, or antihypertensive.
Fishery By-products Fish skin has been used to obtain gelatin that could be used in the preparation of fresh and smoked salmon. Compared to mammalian gelatin, the fish one is characterized by low gelling strength and temperatures as well as good swelling capacity that allow them to be used in capsules of controlled drug release. Natural shrimp and crab shells have been used as substrates for the extraction of food-grade chitosan. This product is sold as a thickener in vegetable oils, an antirancidity agent in meat, antimicrobial agent, edible films, food supplement, emulsifier, and fruit antistaling agent. Collagen extracted from fish skin has various industrial applications in cosmetics and medicine. Key applications of oil with high u-3 fatty acids content include cosmetics or food supplements. Proteins and peptides recovered from fisheries wastes (regardless method used) show promising bioactivities and have been proposed as seafood flavors for soups or surimi, as well as to create new edible food coating able to enlarge the shelf life of food products.
The 5-Stage Universal Recovery Process The extraction, fractionation, and isolation of high value-added components from food waste usually follow the principles of analytical chemistry. Thereafter, modifications are introduced into the applied methodology with an ultimate goal of: 1. 2. 3. 4. 5.
maximizing the yield of the target compounds, suiting the demands of industrial processing, clarifying the high added-value ingredients from impurities and toxic compounds, avoiding loss of functionality during processing, and ensuring the food-grade nature of the final product.
Among the numerous methodologies, five distinct recovery stages can be principally observed. However, steps are often eliminated or oversubscribe each other. Processing moves from the macroscopic to the macromolecular level, prior the extraction, the clarification, and the encapsulation of target compounds in a final product. The so-called 5-Stage Universal Recovery Process is illustrated in Figure 1. This downstream scheme is selected if at least two different components are recovered or the valuable component is a micromolecule (e.g., antioxidant). When the target compound is a macromolecule (e.g., pectin), the second stage may be omitted. The macroscopic pretreatment aims the adjustment of the food waste matrix according to the water content, enzymatic activity, and permeability of the bioresource tissues. This stage includes only one process that is depended on the nature and the structure of the substrate (e.g., solid, sludge, or wastewater). If the substrate is a fruit or vegetable by-product, a wet milling step is necessary to facilitate and improve the yield of the following separation and extraction stages. If the substrate is a wastewater (e.g., of olive oil industry), concentration is utilized with a final purpose of removing water and increasing content of valuable components. Thermal concentration causes activation or deactivation of key enzymes (e.g., polyphenol oxidase), which subsequently affect the yield and the quality of target compounds. Athermal processes (e.g., freeze-drying) possess other disadvantages such as increased cost due to the presence of vacuum conditions. Centrifugation or microfiltration has been suggested in the pretreatment stage, too, because they are able to remove solids, oils, and fats. Alcohol precipitation is the most popular method for the separation of smaller compounds (e.g., antioxidants) from macromolecules (e.g., dietary fiber) that are collected in the so-called alcohol-insoluble residue. This method is selected because it is cheap, nontoxic, and easy to use. However, it is neither selective nor able to separate the complexes between the smaller and the larger molecules. Isoelectric solubilization/precipitation allows the selective solubility of proteins from meat, fish, or marine by-products with concurrent removal of lipids, bones, or the skin. Membranes are also able to perform similar grading procedures,
High Value-Added Compounds from Food Waste
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I. Macroscopic Pre-treatment
I. Macroscopic Pre-treatment Wet Milling, Thermal and/or Vacuum Concentration,
Foam-Mat Drying, Electro-Osmotic Dewatering,
Mechanical Pressing, Freeze Drying, Low-Temperature Plasma Treatment Centrifugation & Microfiltration II. Macro- & Micro- molecules Separation
II. Macro- & Micro- molecules Separation
Alcohol Precipitation, Ultrafiltration,
Colloidal Gas Aphrons, Ultrasound-Assisted
Isoelectric Solubilization-Precipitation,
Crystallization, Pressurized Microwave-
Extrusion
Assisted Extraction III. Extraction
III. Extraction
Ultrasonics, Laser Ablation, Pulsed Electric
Solvent, Acid, Alkali, Microwave-Assisted,
Steam Diffusion, Hydrodistillation,
Field, High Voltage Electrical Discharge,
Supercritical fluid
Liquid Membranes, Pervaporation
IV. Isolation & Purification
IV. Isolation & Purification Magnetic Fishing, Aqueous
Adsorption, Chromatography,
Two-Phase Separation,
Nanofiltration
(a)
Figure 1
Membrane Ion Exchange
Electrodialysis
Chromatography
V. Product formation
V. Product formation Nanotechnology, Pulsed fluid bed agglomeration
Spray- & Freeze-Drying, Emulsions, Extrusion
(b)
Recovery stages of high value-added components from food wastes: (a) conventional and (b) emerging technologies (Galanakis, 2012).
i.e., to remove protein concentrates from cheese whey or separate pectin and potassium during ultrafiltration of high value-added components recovered from olive mill wastewater. Extraction is the important stage of downstream processing, and different techniques may be employed toward the target molecules and their physicochemical characteristics. Enzyme-assisted extraction has been used to soften the structural integrity of botanical materials. Solvent extraction is very convenient, as the solvent provides a physical carrier to transfer the target molecules between different phases. In addition, it can be performed in combination with pressurized and distillation processes, which accelerate the process and extract volatile compounds, respectively. Among the several solvents, ethanol is often preferable because it is cheap and has a food-grade nature. Microwave-assisted extraction raised interest over the last years, as microwave energy is able to heat solvents rapidly and thus accelerating transfer of analytes from the sample matrix into the solvent. Essential oil constituents are traditionally extracted with steam diffusion, although this process has disadvantages such as thermal deterioration and difficult removal of solvent from the extract. Supercritical fluid extraction is employed for difficult separation processes of valuable compounds with low quantity. Advantages include the low solvent consumption, the rapid extraction, and the high selectivity, whereas the difficulty of extracting polar compounds without adding modifiers is the main difficulty. The clarification of target compounds from coextracted impurities could be conducted with several methods. Resin adsorption is an attractive process that enables the separation of selected low molecular weight phenols from dilute solutions with high capacity and insensitivity to toxic substances. Nevertheless, it is time-consuming and demands further research with regard to the sorption behavior of individual components in complex mixtures. Nanofiltration has also been suggested for the clarification of a phenolcontaining beverage derived from olive mill wastewater by removing polymerized phenolic fractions. Owing to its distinguished properties, electrodialysis has been utilized to treat to demineralize oligosaccharides’ extracts from different sources. Although being laboratory-intensive, solvent- and time-consuming, chromatographic methods can ensure the isolation of target molecules in pure forms destined functional food applications. Product formation of antioxidants is performed using encapsulation techniques that are able to entrap bioactive food components inside a coating material, and this way to preserve their stability. In the case of recovering polysaccharides, dietary fibers, or proteins, encapsulation stage is replaced with drying. Spray drying is the most widely used product formation technique in the food industry because it is an economic, flexible, easy handling, and continuous operation. It has been employed for the encapsulation of tomato carotenoids from industrial residues and phenolics from wine lees. The disadvantage of spray drying is the yield reduction caused by the thermal destruction of labile antioxidants. Freeze-drying preserves better the labile compounds compared to spray drying, but it is time- and energy-consuming. Other not-drying methods like liposome and emulsion entrapment are typically used to entrap lipophilic bioactive compounds.
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High Value-Added Compounds from Food Waste
The implementation of the 5-Stage Universal Recovery Process for the recovery of (1) phenols and pectin from apple pomace; (2) antioxidants and dietary fibers from olive mill wastewater; (3) chlorogenic acid, caffeine, melanoidins, and dietary fiber from coffee silverskin; and (4) lactose and different proteins from whey have been referred in detail by Galanakis (2015).
Potential Use of Emerging Technologies Utilization of conventional recovery techniques are often restricted by well-known technological and scale-up boundaries that restrict the efficacy of the proposed methodologies and ultimately their commercial implementation. These include overheating of the food matrix, high energy consumption and high operating cost, loss of functionality and poor stability of the final product, and meeting increasingly stringent legal requirements on materials safety. In addition, consumers in the twenty-first century have high-quality organoleptic standards and demand accurate delivery of the much advertised nutraceuticals inside their body. Although new equipment represent always challenges that require extensive testing, costly investments, and industrial risks, emerging technologies (based on nonthermal concepts) promise to overcome the above challenges and optimize processing efficiency by accelerating heat and mass transfer, shortening of processing time, controlling Maillard reactions, enhancing product functionality, and extending its preservation. The emerging technologies that could be applied within the 5-Stage Universal Recovery Process are presented in Figure 1(b). For instance, high-pressure processing could be used to pretreat waste streams as recently there has been a considerable increase in the number of commercially available foods using this technology for food preservation. Ultrasonication has been used in soy processing in order to enhance protein and sugar yields as well as nisin production. Pulsed electric fields can also be used to recover high value-added compounds from vegetable tissue, and some patents involving a step of compacting the plant tissues and at least one treatment chamber have already been developed. In addition, the extraction of phenolic compounds from grape marc and wine lees using high-voltage electrical discharges and/or pulsed electric fields has been recently patented. Finally, nanoencapsulation is known to enhance product’s stability and bioavailability, by providing moisture- and pH-triggered controlled release.
The Universal Recovery Strategy Food waste is generated in different compositions and forms following the seasonal, regional, and processing characteristics in each case. In addition, this material is already processed and thus susceptible to microbial growth. Subsequently, it requires proper collection in the source, minimum transportation, preservation techniques, as well as fast treatment. It contains lower concentrations of valuable compounds compared to the corresponding food sources, leading to higher processing cost and lower recovery yield. Thus, the development of an economically sustainable and safe methodology for the recapture of high value-added compounds from food waste requires not only a proper management of the used technologies and applied recovery steps, but also a holistic approach that takes into account other important parameters, namely: 1. 2. 3. 4. 5. 6. 7. 8.
waste minimization prior setting up recovery processes, the abundance and distribution of food waste in the source of its generation (e.g., food processing, retailing, households, etc.), the appropriate collection and blending of food waste streams in order to minimize variations in their components’ content, the development of a production line near but not inside the source of generation in order to ensure minimum transportation and at the same time meet HACCP requirements of the food industries, the development of a methodology that provides the highest recovery yield of different products and discharges minimum by-products in the environment, the physical, nondestructive, and food-grade separation of value-added compounds in different streams that allows their reutilization in food products, the enhancement of the functional properties of the final products, and finally the development of constituted products with stable concentration of value-added compounds.
Figure 2 illustrates this holistic approach (called Universal Recovery Strategy) developed (Galanakis, 2015) as extension of the 5Stage Universal Recovery Process (Galanakis, 2012), which is the final step of this strategy. The first step is to identify the different forms and compositions of waste that exist for a target source. Thereafter, all the necessary information concerning food waste availability, distribution, production frequency, and quantities should be collected. The next step includes the collection of samples and a six-level characterization, as illustrated within the box: 1. 2. 3. 4. 5. 6.
determination of macroscopic characteristics (i.e., the different water, oil, and solid phases), determination of microstructure characteristics in order to get an overview of waste matrix, grouping nontarget macro- and micro-molecules, grouping target macro- and micro-molecules, determination of microbial and enzyme load, and determination of the functional properties of the target compounds.
High Value-Added Compounds from Food Waste
Food Waste
7
1st Level: Macroscopic 2nd Level: Microstructure
Identification of different forms 4th Level: Determination
Target macromolecules
Collection of availability, distribution & production data
3rd Level: Group of
compounds Non-target macromolecules 6th Level: Functional properties of target compounds
Collection of samples
5th Level: Microbial & enzymes load
4th Level: Determination
Target micromolecules
3rd Level: Group of
compounds
Characterization
Non-target micromolecules
5 Stages-Universal Recovery Processing
Final Products
Figure 2
The Universal Recovery Strategy (Galanakis, 2015).
Implementation of the Strategy to Develop Industrially Viable Products Not only the involved processes and the recovery approach are of particular interest. A working strategy focused absolutely on the extraction technologies and not on the investigation of tailor-made applications is doomed to fail. To this prospect, it is very important to provide clean label ingredients for processed food products, without impacting flavor or texture and while maintaining minimum shelf-life requirements. Common problems often arise by the market needs for healthier products. Authorities around the world have tightened up the way in which companies can advertise health benefits. For instance, in the European Union, health claims have only been approved for a small number of compounds (e.g., hydroxytyrosol in olive oil) and products (e.g., cholesterol-reducing yogurts and butters). The policy is driven by the need of protecting consumers from dubious claims. Nevertheless, demonstration of proven health benefits is very costly for the companies activated in the field. This fact creates implications for stifling innovation in the field, as claims rejection risk is too high and the obtainment of the required data is not affordable for most companies (typically start-ups) activated in the field. The legislation challenges regulating health beneficial dietary products are lying to the specificity of the products, which have the characteristics of both food and biologically active ingredients. It is advisable to clearly define the manufacturing and quality control criteria related to composition and content range of active substances as well as manufacturing development of product. A clearer label of the dietary supplements, functional food, and products containing recovered value-added components would provide much better insight into the quality and composition of products, and would enable nutritionists to be more confident when recommending these products. To prevent stifling of innovation from the strict regulations, a new direction is needed. Perhaps the establishment of a new label (similar to organic foods) or reduced tax to relevant products could reveal the potentiality of recovering high value-added ingredients from food by-products and reutilizing them in foods. In general, the key point for commercialization is to develop a recovery strategy that allows flexibility and provide alternative scenarios for each stage of processing. The addition of green solvents and safer materials (possessing GRAS status), the implementation of nonthermal technologies, and the selection of minimum recovery steps are strongly recommended. The development of tailor-made applications for the recovered products is necessary, as target compounds may not be as beneficial as proposed theoretically. Product formation (the fifth one from the 5-Stages Universal Recovery Process) is the most essential step, as encapsulation enhances functionality and extents the shelf life of the products.
Further Reading Galanakis, C.M., 2015. Food Waste Recovery: Processing Technologies and Industrial Techniques. Academic Press, London. High Value-Added Ingredients of Food Waste: Mullen, A.M., Alvarez, C., Pojic, M., Hadnadev, T.D., Papageorgiou, M., 2015. Classification and target compounds. In: Galanakis, C.M. (Ed.), Food Waste Recovery: Processing Technologies and Industrial Techniques.
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High Value-Added Compounds from Food Waste
Galanakis, C.M., 2015. Separation of functional macromolecules and micromolecules: from ultrafiltration to the border of nanofiltration. Trends Food Sci. Technol. 42, 44–63. Commercialized Applications: Galanakis, C.M., Martínez-Saez, N., del Castillo, M.D., Barba, F.J., Mitropoulou, V.S., 2015. Chapter 15: patented and commercialized applications. In: Galanakis, C.M. (Ed.), Food Waste Recovery: Processing Technologies and Industrial Techniques. The 5-Stage Universal Recovery Process: Galanakis, C.M., 2012. Recovery of high added-value components from food wastes: conventional, emerging technologies and commercialized applications. Trends Food Sci. Technol. 26, 68–87. Potential Application of Emerging Technologies in the Field: Galanakis, C.M., Barba, F.J., Prasad, K.N., 2015. Cost and safety issues of emerging technologies against conventional techniques. In: Galanakis, C.M. (Ed.), Food Waste Recovery: Processing Technologies and Industrial Techniques. The Universal Recovery Strategy: Galanakis, C.M., 2015. The universal recovery strategy. In: Galanakis, C.M. (Ed.), Food Waste Recovery: Processing Technologies and Industrial Techniques. Implementation of the Strategy to Develop Industrially Viable Products: Galanakis, C.M., Martínez-Saez, N., del Castillo, M.D., Barba, F.J., Mitropoulou, V.S., 2015. Patented and commercialized applications. In: Galanakis, C.M. (Ed.), Food Waste Recovery: Processing Technologies and Industrial Techniques. Trends and Updates in the Field: http://charismgalanakis.blogspot.gr/.
Introduction Food Waste Sources and Value-Added Compounds Applications Vegetable and Plant By-products Olive By-products Coffee By-products Dairy By-products Animal By-products Fishery By-products The 5-Stage Universal Recovery Process Potential Use of Emerging Technologies The Universal Recovery Strategy Implementation of the Strategy to Develop Industrially Viable Products Further Reading
1 1 3 3 3 3 3 4 4 4 6 6 7 7
Introduction Until the end of the twentieth century, disposal of food waste was not considered as a matter of concern. Particularly, increase of food production without improving the efficiency of the food systems was the prevalent policy. This consideration increased generation of wasted food along supply chains. In the twenty-first century, escalating demands for processed foods have required identification of concrete directions to minimize energy demands and economic costs as well as reduce food waste. The perpetual disposal of high value-added materials in the environment is a practice that could not be continuing for a long time within the sustainability and bioeconomy frame of the modern food industry. The depletion of food sources, the fast-growing population, and the increasing need for nutritionally proper diets do not allow considering other alternatives. Up to the very recent years, the main methodologies for waste minimization and valorization included general methods such as incineration, anaerobic fermentation, biofuel conversion methods, composting and vermicomposting, landfill, or agricultural applications like animal feed and fertilizers. Subsequently, the potential of food waste to create new opportunities and markets was underestimated. Nowadays, consumers’ consciousness about environmental issues and legislative pressures increase the requirements of new management methods and treatments that focus on the recovery of value-added components from food waste and their reutilization in foodstuff. The recovered components typically improve targeted aspects of the final product quality. Value-added properties can be related to the shelf life or color of the final product, health benefits, formulation, or other product feature. Regardless of the branch of the food industry under investigation, waste streams are generated across various stages of the supply chain. For nutraceutical applications or conversion of by-products into chemicals, valuable components should be extracted from the matrix in appropriate way. Processing by-products of food and agricultural industry is of particular interest because of their abundance and existence in concentrated locations. Depending on the source (excluding meat and fish), these can be less susceptible to deterioration compared to the wastes produced at the end of food supply chain. Waste produced at the end of the chain tends to be highly dispersed (e.g., in individual households). This fact complicates their valorization as sources for value-added components recovery due to the need for an additional collection step and the reduced biological stability due to microbial growth. Due to regulatory and technical reasons, such as traceability and health and safety issues, by-products with a high potential for valorization are fruit- and vegetable-derived waste.
Food Waste Sources and Value-Added Compounds Food waste is composed of complex ingredients that have been discharged from the original sources. The waste streams that are originated by various branches of the food industry can be divided in two main groups (plant or animal origin) and seven subcategories (Table 1). Wheat grinding and rice dehulling produce bran and straw that are rich in high nutritional proteins and glucuronoarabinoxylans. Oat-processing waste has been proposed for the extraction of dietary fiber and particularly b-glucan. Potato processing during chips or french fries production generates phenol-rich solid wastes (e.g., peels or cull potatoes). Cassava peel has been proposed as a substrate for microbial protein enrichment. Sunflower and soybean seeds have been used to extract phytosterols. Besides, due to their high protein content, pulses processing by-products could be used in meat
Reference Module in Food Sciences
http://dx.doi.org/10.1016/B978-0-08-100596-5.03510-1
1
2
High Value-Added Compounds from Food Waste
Table 1
Food wastes origin, sources, and respective high value-added compounds for recovery
Waste origin
Selected sources
Target ingredients
Plant 1. Cereals
Rice bran
Albumin and globulin Hemicellulose B and insoluble dietary fiber Arabinoxylans Hemicellulose Glucuronoarabinoxylans b-Glucan Glucose, arabinose, and galactose Arabinoxylans Phenols Organic acids Phytosterols Phytosterols Phytosterols Albumin Phenols Phenols and pectin Narirutin Hesperidin Apocarotenoid Limonene Pectin Pectin Phenols Pectin Protein Dietary fiber Phenols Calcium tartrate Enocyanin Cyanidin-3-rutinoside Soluble and insoluble dietary fiber b-carotene Phenols Lycopene Carotenoids Pectin
2. Roots and tubers 3. Oilcrops and pulses
4. Fruits and vegetables
Wheat middling Wheat straw Wheat bran Oat mill waste Malt dust Brewery’s spent grains Potato peel Sugar beet molasses Sunflower seed Soybean seed Soybean oil waste Soybean wastewater Olive pomace Olive mill wastewater Cold hardy mandarin peel Orange peel
Lemon by-product Apple pomace Apple skin Peach pomace Apricot kernel Grape pomace Grape skin Wine lees Banana peel Rejected and processed kiwifruits Carrot peel Tomato pomace Tomato skin Cauliflower floret and curd Animal 5. Meat products
6. Fish and seafood
Chicken by-products Slaughterhouse by-products Bovine blood Beef lung Sheep visceral mass Fish leftovers (skin, head, and bones)
7. Dairy products
Shrimp and crab shells Surimi wastewater Cheese whey
Proteins Proteins Proteins Protein concentrates Protein hydrolysates Proteins Lipids Chitosan/Chitin Proteins Lactose b-Lactoglobulin a-Lactalbumin
Adapted from Galanakis, C.M., 2012. Recovery of high added-value components from food wastes: conventional, emerging technologies and commercialized applications. Trends Food Sci. Technol. 26, 68–87.
and pasta production, ready-to-eat breakfast cereals, baby food, snack food, texturized vegetable protein, pet foods, dried soups, and dry beverages. Animal, fish, and seafood processing by-products (e.g., bones, tendons, skin, head, beef lung, or sheep visceral mass) contain high amount of proteins and lipids. Value-added compounds recovered from food waste are used today as additives in foodstuff due to their ability to provide advanced technological properties and health claims, respectively, to the final product.
High Value-Added Compounds from Food Waste
3
Applications Vegetable and Plant By-products Most fruit (e.g., apple) and vegetable (e.g., carrot) by-products are rich sources of dietary fiber and natural antioxidants. Water-insoluble fiber (e.g., hemicelluloses) is able to improve intestinal regulation and thereby is destined to supplement food products or ready meals. Soluble dietary fiber (e.g., pectin) is known for its ability to lower blood lipid level and at the same time possesses advanced gelling properties that allow its application as thickener, emulsion stabilizer, and fat replacement in foods. Pectin is known to possess a variety of pharmacological activities such as antimetastasis and antiulcer activities. Besides, a regular generous intake of dietary fiber reduces risk for developing coronary heart disease, stroke, hypertension, diabetes, obesity, and certain gastrointestinal diseases. Natural antioxidants (e.g., phenols, carotenoids, tocopherols, and ascorbic acid) have been connected to both nutritional (reduction of oxidative stress, prevention of cancer, arteriosclerosis, ageing processes) and functional properties like natural food and beverage preservatives since they extend the shelf life of the product by delaying the formation of off-flavors and rancidity. Industrial commercialization of citrus peel is conducted for more than 30 years, whereas the recovered ‘sugar syrup’ contains essential oils, flavonoids (e.g., narirutin, hesperidin, etc.), carotenoids, sugar, and pectin. The latter product is used as a sweetener and flavor substance in juices, replacing artificial compounds, such as saccharine or aspartame. Due to the high concentrations of biologically active secondary metabolites remaining in citrus peel molasses, this raw material is also suitable as a source for functional food and/or food supplement ingredients. The industrial recovery of water-insoluble carotenoids (e.g., lycopene) from food wastes is under progress. Carotenoids act in prevention of cardiovascular diseases and specific cancers, whereas they are important dietary sources of vitamin A. Indeed, lycopene is one of the most popular natural pigments (red). Recently, the Food and Drug Administration (FDA) approved the use of higher levels of tomato lycopene to color processed meats, as alternative to carmine. Moreover, Food Safety and Inspection Service has established that tomato lycopene extracts and concentrates (GRN 000156) of 50 and 100 mg kg 1, respectively, could be used as coloring agent in ready-to-eat meat, poultry, and egg products.
Olive By-products At least five companies around the world recover phenols and particularly hydroxytyrosol from olive mill wastewater and sell them as natural preservatives, life-prolonging agents, or bioactive additives in vegetable oils, chocolates, bakery, meat products, and cosmetics. Hidrox is a commercially available product from CreAgri (Hayward, USA) with a high content of hydroxytyrosol and several beneficial (e.g., anti-inflammatory and antimicrobial) properties. Other relevant phenol-rich products include Olivactiv (Glanbia, Milan, Italy), Oleaselect, Opextan (Indena, Milan, Italy), Olive Braun Standard 500 from Naturex, olive polyphenols from Albert Isliker, Prolivols from Seppic Inc., Olive Polyphenols NLT from Lalilab Inc., Phenolea Complex Plus from PhenoPharm, and Lundolive P1100 from Phenoliv AB. Olive pulp extracts (in general) have been approved by FDA with GRAS status (GRN No. 459) for being used as an antioxidant in baked goods, beverages, cereals, sauces and dressings, seasonings, snacks, and functional foods at a level up to 3000 mg kg 1 in the final food. Besides, pectin derived from olive mill wastewater has been proved to restrict oil uptake of low-fat meatballs during deep fat frying.
Coffee By-products Coffee silverskin contains several bioactive compounds such as prebiotic carbohydrates, dietary fiber, and antioxidants. In agreement, patented extracts recovered from coffee silverskin contain high amounts of chlorogenic acid and caffeine, whereas their antioxidant activity survives the in vitro gastrointestinal digestion process and remain bioaccessible. Therefore, they have been proposed as an antioxidant additive in food and cosmetics manufacture, with potential excipient (preservative, flavoring) functions as well as antioxidant, anti-ageing, and anticellulite activities. Spent coffee grounds have been employed for the inventions of foods and beverages containing mannooligosaccharides, ultimately to reduce blood pressure, elevate suppressing effect, and reduce abdominal fat. They have also been used as ingredients in bakery products, pastry, confectionery, biscuits, and breakfast cereals. Finally, a gluten-free product has been recovered (Coffee flour) from coffee cherry (the surrounding pulp) and commercialized as additive in breads, cookies, muffins, squares, brownies, pastas, sauces, and beverages.
Dairy By-products Direct application of whey implies its utilization as a water replacer without any changes in its composition. This is the case of soft whey-based beverages production, wherein native sweet, diluted, or acid whey is mixed with different additives. Whey is also used to produce beverages obtained by fermentation with probiotic bacteria. On the other hand, dried whey powder could be utilized by dairy, baking, confectionary, baby food, and meat industry. The main target compounds of cheese whey for recovery purposes include casein fines, protein concentrates and lactose that are used as fat replacers, flavor enhancers, stabilizers, and nutritional supplements in foods, beverages, and confectionary. Whey proteins are characterized by their exceptionally high nutritional quality, predominantly determined by amino acid composition and physiological functionality. They possess also unique physical functional properties such as gelling, foaming, water binding, and emulsifying capacity. Hydrolyzed whey
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High Value-Added Compounds from Food Waste
proteins are known for their ability to reduce total and LDL cholesterol levels in mammals and thus could be used for the production of functional foods. APS BioGroup produces several commercial products from whey, such as colostrum and ImmuloxÒ powders, with immune system balancing effects and high level of proline-rich peptides. Ultimately, crude whey lactose is used as aroma stabilizer and sweetener.
Animal By-products Waste skimming sludge has typically an important nutritional value for feed applications, whereas chicken feathers have been used as a source of keratin for packaging uses. Collagen and gelatin from pig, ducks, and bovine skins can be recovered and used as a source of bioactive peptides after enzymatic treatment. Collagen can be used in gene transferring, by subcutaneous collagenous pellets for somatic gene therapy or for probiotic bacteria microencapsulation by spray-drying technology. Blood is a by-product of the meat industry with high content of good-quality proteins. Whole proteins (as albumin, fibrinogen, and globulins) can be separated from plasma. They have relevant functional properties like gelation, foaming, emulsifying, or thickening, which allow them to be utilized in the food industry as dietary supplements. More recent applications of blood proteins include the development of products with enhanced functional properties such as antioxidant, antimicrobial, mineral-binding, antigenotoxic, opioid, or antihypertensive.
Fishery By-products Fish skin has been used to obtain gelatin that could be used in the preparation of fresh and smoked salmon. Compared to mammalian gelatin, the fish one is characterized by low gelling strength and temperatures as well as good swelling capacity that allow them to be used in capsules of controlled drug release. Natural shrimp and crab shells have been used as substrates for the extraction of food-grade chitosan. This product is sold as a thickener in vegetable oils, an antirancidity agent in meat, antimicrobial agent, edible films, food supplement, emulsifier, and fruit antistaling agent. Collagen extracted from fish skin has various industrial applications in cosmetics and medicine. Key applications of oil with high u-3 fatty acids content include cosmetics or food supplements. Proteins and peptides recovered from fisheries wastes (regardless method used) show promising bioactivities and have been proposed as seafood flavors for soups or surimi, as well as to create new edible food coating able to enlarge the shelf life of food products.
The 5-Stage Universal Recovery Process The extraction, fractionation, and isolation of high value-added components from food waste usually follow the principles of analytical chemistry. Thereafter, modifications are introduced into the applied methodology with an ultimate goal of: 1. 2. 3. 4. 5.
maximizing the yield of the target compounds, suiting the demands of industrial processing, clarifying the high added-value ingredients from impurities and toxic compounds, avoiding loss of functionality during processing, and ensuring the food-grade nature of the final product.
Among the numerous methodologies, five distinct recovery stages can be principally observed. However, steps are often eliminated or oversubscribe each other. Processing moves from the macroscopic to the macromolecular level, prior the extraction, the clarification, and the encapsulation of target compounds in a final product. The so-called 5-Stage Universal Recovery Process is illustrated in Figure 1. This downstream scheme is selected if at least two different components are recovered or the valuable component is a micromolecule (e.g., antioxidant). When the target compound is a macromolecule (e.g., pectin), the second stage may be omitted. The macroscopic pretreatment aims the adjustment of the food waste matrix according to the water content, enzymatic activity, and permeability of the bioresource tissues. This stage includes only one process that is depended on the nature and the structure of the substrate (e.g., solid, sludge, or wastewater). If the substrate is a fruit or vegetable by-product, a wet milling step is necessary to facilitate and improve the yield of the following separation and extraction stages. If the substrate is a wastewater (e.g., of olive oil industry), concentration is utilized with a final purpose of removing water and increasing content of valuable components. Thermal concentration causes activation or deactivation of key enzymes (e.g., polyphenol oxidase), which subsequently affect the yield and the quality of target compounds. Athermal processes (e.g., freeze-drying) possess other disadvantages such as increased cost due to the presence of vacuum conditions. Centrifugation or microfiltration has been suggested in the pretreatment stage, too, because they are able to remove solids, oils, and fats. Alcohol precipitation is the most popular method for the separation of smaller compounds (e.g., antioxidants) from macromolecules (e.g., dietary fiber) that are collected in the so-called alcohol-insoluble residue. This method is selected because it is cheap, nontoxic, and easy to use. However, it is neither selective nor able to separate the complexes between the smaller and the larger molecules. Isoelectric solubilization/precipitation allows the selective solubility of proteins from meat, fish, or marine by-products with concurrent removal of lipids, bones, or the skin. Membranes are also able to perform similar grading procedures,
High Value-Added Compounds from Food Waste
5
I. Macroscopic Pre-treatment
I. Macroscopic Pre-treatment Wet Milling, Thermal and/or Vacuum Concentration,
Foam-Mat Drying, Electro-Osmotic Dewatering,
Mechanical Pressing, Freeze Drying, Low-Temperature Plasma Treatment Centrifugation & Microfiltration II. Macro- & Micro- molecules Separation
II. Macro- & Micro- molecules Separation
Alcohol Precipitation, Ultrafiltration,
Colloidal Gas Aphrons, Ultrasound-Assisted
Isoelectric Solubilization-Precipitation,
Crystallization, Pressurized Microwave-
Extrusion
Assisted Extraction III. Extraction
III. Extraction
Ultrasonics, Laser Ablation, Pulsed Electric
Solvent, Acid, Alkali, Microwave-Assisted,
Steam Diffusion, Hydrodistillation,
Field, High Voltage Electrical Discharge,
Supercritical fluid
Liquid Membranes, Pervaporation
IV. Isolation & Purification
IV. Isolation & Purification Magnetic Fishing, Aqueous
Adsorption, Chromatography,
Two-Phase Separation,
Nanofiltration
(a)
Figure 1
Membrane Ion Exchange
Electrodialysis
Chromatography
V. Product formation
V. Product formation Nanotechnology, Pulsed fluid bed agglomeration
Spray- & Freeze-Drying, Emulsions, Extrusion
(b)
Recovery stages of high value-added components from food wastes: (a) conventional and (b) emerging technologies (Galanakis, 2012).
i.e., to remove protein concentrates from cheese whey or separate pectin and potassium during ultrafiltration of high value-added components recovered from olive mill wastewater. Extraction is the important stage of downstream processing, and different techniques may be employed toward the target molecules and their physicochemical characteristics. Enzyme-assisted extraction has been used to soften the structural integrity of botanical materials. Solvent extraction is very convenient, as the solvent provides a physical carrier to transfer the target molecules between different phases. In addition, it can be performed in combination with pressurized and distillation processes, which accelerate the process and extract volatile compounds, respectively. Among the several solvents, ethanol is often preferable because it is cheap and has a food-grade nature. Microwave-assisted extraction raised interest over the last years, as microwave energy is able to heat solvents rapidly and thus accelerating transfer of analytes from the sample matrix into the solvent. Essential oil constituents are traditionally extracted with steam diffusion, although this process has disadvantages such as thermal deterioration and difficult removal of solvent from the extract. Supercritical fluid extraction is employed for difficult separation processes of valuable compounds with low quantity. Advantages include the low solvent consumption, the rapid extraction, and the high selectivity, whereas the difficulty of extracting polar compounds without adding modifiers is the main difficulty. The clarification of target compounds from coextracted impurities could be conducted with several methods. Resin adsorption is an attractive process that enables the separation of selected low molecular weight phenols from dilute solutions with high capacity and insensitivity to toxic substances. Nevertheless, it is time-consuming and demands further research with regard to the sorption behavior of individual components in complex mixtures. Nanofiltration has also been suggested for the clarification of a phenolcontaining beverage derived from olive mill wastewater by removing polymerized phenolic fractions. Owing to its distinguished properties, electrodialysis has been utilized to treat to demineralize oligosaccharides’ extracts from different sources. Although being laboratory-intensive, solvent- and time-consuming, chromatographic methods can ensure the isolation of target molecules in pure forms destined functional food applications. Product formation of antioxidants is performed using encapsulation techniques that are able to entrap bioactive food components inside a coating material, and this way to preserve their stability. In the case of recovering polysaccharides, dietary fibers, or proteins, encapsulation stage is replaced with drying. Spray drying is the most widely used product formation technique in the food industry because it is an economic, flexible, easy handling, and continuous operation. It has been employed for the encapsulation of tomato carotenoids from industrial residues and phenolics from wine lees. The disadvantage of spray drying is the yield reduction caused by the thermal destruction of labile antioxidants. Freeze-drying preserves better the labile compounds compared to spray drying, but it is time- and energy-consuming. Other not-drying methods like liposome and emulsion entrapment are typically used to entrap lipophilic bioactive compounds.
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High Value-Added Compounds from Food Waste
The implementation of the 5-Stage Universal Recovery Process for the recovery of (1) phenols and pectin from apple pomace; (2) antioxidants and dietary fibers from olive mill wastewater; (3) chlorogenic acid, caffeine, melanoidins, and dietary fiber from coffee silverskin; and (4) lactose and different proteins from whey have been referred in detail by Galanakis (2015).
Potential Use of Emerging Technologies Utilization of conventional recovery techniques are often restricted by well-known technological and scale-up boundaries that restrict the efficacy of the proposed methodologies and ultimately their commercial implementation. These include overheating of the food matrix, high energy consumption and high operating cost, loss of functionality and poor stability of the final product, and meeting increasingly stringent legal requirements on materials safety. In addition, consumers in the twenty-first century have high-quality organoleptic standards and demand accurate delivery of the much advertised nutraceuticals inside their body. Although new equipment represent always challenges that require extensive testing, costly investments, and industrial risks, emerging technologies (based on nonthermal concepts) promise to overcome the above challenges and optimize processing efficiency by accelerating heat and mass transfer, shortening of processing time, controlling Maillard reactions, enhancing product functionality, and extending its preservation. The emerging technologies that could be applied within the 5-Stage Universal Recovery Process are presented in Figure 1(b). For instance, high-pressure processing could be used to pretreat waste streams as recently there has been a considerable increase in the number of commercially available foods using this technology for food preservation. Ultrasonication has been used in soy processing in order to enhance protein and sugar yields as well as nisin production. Pulsed electric fields can also be used to recover high value-added compounds from vegetable tissue, and some patents involving a step of compacting the plant tissues and at least one treatment chamber have already been developed. In addition, the extraction of phenolic compounds from grape marc and wine lees using high-voltage electrical discharges and/or pulsed electric fields has been recently patented. Finally, nanoencapsulation is known to enhance product’s stability and bioavailability, by providing moisture- and pH-triggered controlled release.
The Universal Recovery Strategy Food waste is generated in different compositions and forms following the seasonal, regional, and processing characteristics in each case. In addition, this material is already processed and thus susceptible to microbial growth. Subsequently, it requires proper collection in the source, minimum transportation, preservation techniques, as well as fast treatment. It contains lower concentrations of valuable compounds compared to the corresponding food sources, leading to higher processing cost and lower recovery yield. Thus, the development of an economically sustainable and safe methodology for the recapture of high value-added compounds from food waste requires not only a proper management of the used technologies and applied recovery steps, but also a holistic approach that takes into account other important parameters, namely: 1. 2. 3. 4. 5. 6. 7. 8.
waste minimization prior setting up recovery processes, the abundance and distribution of food waste in the source of its generation (e.g., food processing, retailing, households, etc.), the appropriate collection and blending of food waste streams in order to minimize variations in their components’ content, the development of a production line near but not inside the source of generation in order to ensure minimum transportation and at the same time meet HACCP requirements of the food industries, the development of a methodology that provides the highest recovery yield of different products and discharges minimum by-products in the environment, the physical, nondestructive, and food-grade separation of value-added compounds in different streams that allows their reutilization in food products, the enhancement of the functional properties of the final products, and finally the development of constituted products with stable concentration of value-added compounds.
Figure 2 illustrates this holistic approach (called Universal Recovery Strategy) developed (Galanakis, 2015) as extension of the 5Stage Universal Recovery Process (Galanakis, 2012), which is the final step of this strategy. The first step is to identify the different forms and compositions of waste that exist for a target source. Thereafter, all the necessary information concerning food waste availability, distribution, production frequency, and quantities should be collected. The next step includes the collection of samples and a six-level characterization, as illustrated within the box: 1. 2. 3. 4. 5. 6.
determination of macroscopic characteristics (i.e., the different water, oil, and solid phases), determination of microstructure characteristics in order to get an overview of waste matrix, grouping nontarget macro- and micro-molecules, grouping target macro- and micro-molecules, determination of microbial and enzyme load, and determination of the functional properties of the target compounds.
High Value-Added Compounds from Food Waste
Food Waste
7
1st Level: Macroscopic 2nd Level: Microstructure
Identification of different forms 4th Level: Determination
Target macromolecules
Collection of availability, distribution & production data
3rd Level: Group of
compounds Non-target macromolecules 6th Level: Functional properties of target compounds
Collection of samples
5th Level: Microbial & enzymes load
4th Level: Determination
Target micromolecules
3rd Level: Group of
compounds
Characterization
Non-target micromolecules
5 Stages-Universal Recovery Processing
Final Products
Figure 2
The Universal Recovery Strategy (Galanakis, 2015).
Implementation of the Strategy to Develop Industrially Viable Products Not only the involved processes and the recovery approach are of particular interest. A working strategy focused absolutely on the extraction technologies and not on the investigation of tailor-made applications is doomed to fail. To this prospect, it is very important to provide clean label ingredients for processed food products, without impacting flavor or texture and while maintaining minimum shelf-life requirements. Common problems often arise by the market needs for healthier products. Authorities around the world have tightened up the way in which companies can advertise health benefits. For instance, in the European Union, health claims have only been approved for a small number of compounds (e.g., hydroxytyrosol in olive oil) and products (e.g., cholesterol-reducing yogurts and butters). The policy is driven by the need of protecting consumers from dubious claims. Nevertheless, demonstration of proven health benefits is very costly for the companies activated in the field. This fact creates implications for stifling innovation in the field, as claims rejection risk is too high and the obtainment of the required data is not affordable for most companies (typically start-ups) activated in the field. The legislation challenges regulating health beneficial dietary products are lying to the specificity of the products, which have the characteristics of both food and biologically active ingredients. It is advisable to clearly define the manufacturing and quality control criteria related to composition and content range of active substances as well as manufacturing development of product. A clearer label of the dietary supplements, functional food, and products containing recovered value-added components would provide much better insight into the quality and composition of products, and would enable nutritionists to be more confident when recommending these products. To prevent stifling of innovation from the strict regulations, a new direction is needed. Perhaps the establishment of a new label (similar to organic foods) or reduced tax to relevant products could reveal the potentiality of recovering high value-added ingredients from food by-products and reutilizing them in foods. In general, the key point for commercialization is to develop a recovery strategy that allows flexibility and provide alternative scenarios for each stage of processing. The addition of green solvents and safer materials (possessing GRAS status), the implementation of nonthermal technologies, and the selection of minimum recovery steps are strongly recommended. The development of tailor-made applications for the recovered products is necessary, as target compounds may not be as beneficial as proposed theoretically. Product formation (the fifth one from the 5-Stages Universal Recovery Process) is the most essential step, as encapsulation enhances functionality and extents the shelf life of the products.
Further Reading Galanakis, C.M., 2015. Food Waste Recovery: Processing Technologies and Industrial Techniques. Academic Press, London. High Value-Added Ingredients of Food Waste: Mullen, A.M., Alvarez, C., Pojic, M., Hadnadev, T.D., Papageorgiou, M., 2015. Classification and target compounds. In: Galanakis, C.M. (Ed.), Food Waste Recovery: Processing Technologies and Industrial Techniques.
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High Value-Added Compounds from Food Waste
Galanakis, C.M., 2015. Separation of functional macromolecules and micromolecules: from ultrafiltration to the border of nanofiltration. Trends Food Sci. Technol. 42, 44–63. Commercialized Applications: Galanakis, C.M., Martínez-Saez, N., del Castillo, M.D., Barba, F.J., Mitropoulou, V.S., 2015. Chapter 15: patented and commercialized applications. In: Galanakis, C.M. (Ed.), Food Waste Recovery: Processing Technologies and Industrial Techniques. The 5-Stage Universal Recovery Process: Galanakis, C.M., 2012. Recovery of high added-value components from food wastes: conventional, emerging technologies and commercialized applications. Trends Food Sci. Technol. 26, 68–87. Potential Application of Emerging Technologies in the Field: Galanakis, C.M., Barba, F.J., Prasad, K.N., 2015. Cost and safety issues of emerging technologies against conventional techniques. In: Galanakis, C.M. (Ed.), Food Waste Recovery: Processing Technologies and Industrial Techniques. The Universal Recovery Strategy: Galanakis, C.M., 2015. The universal recovery strategy. In: Galanakis, C.M. (Ed.), Food Waste Recovery: Processing Technologies and Industrial Techniques. Implementation of the Strategy to Develop Industrially Viable Products: Galanakis, C.M., Martínez-Saez, N., del Castillo, M.D., Barba, F.J., Mitropoulou, V.S., 2015. Patented and commercialized applications. In: Galanakis, C.M. (Ed.), Food Waste Recovery: Processing Technologies and Industrial Techniques. Trends and Updates in the Field: http://charismgalanakis.blogspot.gr/.