Tổng quan đánh giá về các sản phẩm protein đơn bào (SCP) từ nấm mốc. Lựa chọn hệ nấm mốc trong công nghệ sản xuất Protein đơn bào. Cải tiến công nghệ sản xuất protein đơn bào. Đánh giá chất lượng Protein trong SCP được sản xuất từ nấm mốc.
SINGLE CELL PROTEIN Contents Mycelial Fungi The Algae Yeasts and Bacteria Mycelial Fungi PS Nigam, University of Ulster, Coleraine, UK A Singh, Technical University of Denmark, Lyngby, Denmark Ó 2014 Elsevier Ltd All rights reserved This article is a revision of the previous edition article by Poonam Nigam, volume 3, pp 2034–2044, Ó 1999, Elsevier Ltd Introduction The extent of shortfall in protein varies from country to country and must be considered within the framework of each national economy The shift from grain to meat diets in industrial and developing countries is of dramatic proportions and leads to a much higher per capita grain consumption, since it takes 3–10 kg of grain to produce kg of meat by animal rearing and fattening programs The experimental use of microbes as protein producers has been widely successful This field of study has become known as single-cell protein (SCP) production, referring to the fact that most microorganisms used as producers grow as single or filamentous individuals rather than as complex multicellular organisms, such as plants or animals Eating microbes may seem strange, but people have long recognized the nutritional value of the large fruiting bodies of some fungi, that is, mushrooms Mushroom growing, because of its antiquity, can be considered a conventional type of food production This article is concerned with novel processes for growing fungal mycelia, which lend themselves to biotechnological processing The pioneering research on SCP production, conducted by Max Delbriick and coworker in Berlin, about one century ago, highlighted the potential use of surplus brewer’s yeast as a feeding supplement for animals The term SCP was coined in the 1960s to embrace microbial biomass produced by fermentation The SCP production technologies developed as a promising way to cultivate enough protein for the world’s protein hunger Over the past two decades, there has been a growing interest in using microbes for food production, in particular for feeding domesticated food-producing animals such as poultry Use of SCP derived from low-value waste materials for animal feed may increase the food available to humans by reducing competition between humans and animals for protein-rich vegetable foods Major companies throughout the world have Encyclopedia of Food Microbiology, Volume long been involved in developing SCP processes, and many SCP products are now commercially available SCP may be used as a protein supplement, as a food additive to improve flavor or fat binding, or as a replacement for animal protein in the diet Microorganisms have high DNA and RNA contents and human metabolism of nucleic acids yields excessive amounts of uric acid, which may cause kidney stones and gout Because humans have a limited capacity to degrade nucleic acids, additional processing is required before SCP can be used in human foods In animal feeding, SCP may serve as a replacement for such traditional protein supplements as fish meal and soy meal The high protein levels and bland odor and taste of SCP, together with ease of storage, make SCP a potentially attractive component of manufactured foods Also its high protein content makes it attractive for feeding farmed crustacea and fish Significance of Single-Cell Protein Microorganisms produce protein much more efficiently than any farm animal (Table 1) The yields of protein from a 250 kg cow and 250 g of microorganisms are comparable The cow will produce 200 g of protein per day, whereas the microbes, in theory, can produce 25 tons in the same time under ideal growing conditions The advantages of using microbes for SCP production are outlined in Table Choice of Mycelial Fungi in Biotechnology Currently, fungi are used for the production of secondary metabolites of medicinal and industrial importance (antibiotics, mycotoxins, and fermented foods) Filamentous fungi also play a significant role in the food industry, for example, adding flavor to certain cheeses and in the production of http://dx.doi.org/10.1016/B978-0-12-384730-0.00311-6 415 416 SINGLE CELL PROTEIN j Mycelial Fungi Table Time required to double the mass of various organisms Organism Doubling time Bacteria and yeasts Molds and algae Grass and some plants Chickens Pigs Cattle (young) 20–120 2–6 h 1–2 weeks 2–4 weeks 4–6 weeks 1–2 months Table The advantages of using microbes for single-cell protein production Microorganisms can grow at remarkably rapid rates under optimum conditions; some microbes can double their mass every 30–60 Microorganisms are more easily genetically modified than plants and animals; they are more amenable to large-scale screening programs to select for higher growth rate and improved RNA content and can be subjected more easily to gene transfer technology Microorganisms have a relatively high protein content and the nutritional value of the protein is good Microorganisms can be grown in vast numbers in relatively small continuous fermentation processes, using a relatively small land area, and growth is independent of climate Microorganisms can grow on a wide range of raw materials, including low-value agri-industrial residues and by-products The production is independent of seasonal and climatic variations oriental foods (Table 3) They are used as a major protein source in some food additives and extenders and to improve the protein content of animal feeds In the previous examples, the filamentous fungi, although playing an important role, are generally a minor component of the final product It is possible, however, to utilize the physical characteristics of these fungi to assemble structured food products whose sensory textures are similar to muscle tissue food products An example of this approach is given in the following section Texture and Flavor of Mycoprotein In addition to the growth rates of organisms used for SCP, their conversion of substrate to protein is much more efficient than conversion of feed by farm animals This is shown in Table The filamentous morphology of the fungi means that the mycelial mass has a natural texture, which can be used to impart a meatlike texture to the product, which may also be favored and colored to resemble meat The coarseness of the texture depends on the length of the hyphae, which can be controlled by adjusting the growth rate Commercial Exploitation of Mycelial Fungi The following characteristics determine the choice of fungi as organisms to be used in a large-scale industrial fermentation process, producing a low-cost final product: l l l l l l Good at breaking down a wide range of complex substrates (e.g., cellulose, hemicellulose, pectin) Can tolerate low pH values, which helps in preventing contamination of the culture Few nutritional requirements Ease of recovery of biomass by filtration Ease of handling and of drying the biomass Structure conferred by hyphae allows the fabrication of textured foods The industrial production of SCP continues to excite attention, particularly in relation to the use of simple carbohydrates as feedstock for microbial growth and biomass production Today, however, the economics of production has shifted the emphasis from the application of SCP to solve the problem of starvation to the production of novel foods for use in advanced economies Features of Commercial Exploitation of Fungi Following are the features of commercial exploitation: l Table Direct food uses of fungi Fungal species Agaricus bisporus Lentinus edodes Volvariella volvacea Flammulina velutipes Pleurotus spp Tuber melanosporum Penicillium roqueforti Penicillium camemberti Monascus purpureus Aspergillus oryzae/A sojae Aspergillus oryzae/A sojae Rhizopus oligosporus Application Edible macrofungi Common edible mushroom Shiitake mushroom Chinese or straw mushroom Winter mushroom Oyster mushroom Truffle Cheeses Roquefort, stilton, blue Camembert, brie, soft-ripened cheeses Oriental food fermentations Ang-kak, anka koji, or beni koki (red rice – culture grown on rice grains) Miso (fermented soybeans) Shoyu (soy) sauce Tempeh or tempe kedele (fermented soybean cotyledons) Rapid growth rate and high protein content compared with plants or animals l Can be produced in large amounts in a relatively small area, using biological by-products as sources of nutrient, such as the by-products from the confectionery and distillery, vegetable and wood-processing industries, although for human food application, the use of food or reagent-grade nutrients is essential l Fungal cells contain carbohydrate, lipids, and nucleic acids, and a favorable balance of lysine, methionine, and tryptophan amino acids that plant proteins often lack For example, fungi can be used to improve the nutritional quality of food grains, such as barley Barley is deficient in lysine, which is normally added to barley feed in the form of expensive proteins such as fish or soy meal Fungal supplementation is achieved by adding a nitrogen source to a barley gruel and then inoculating it with an amylolytic (starchdecomposing) fungus, such as Aspergillus oryzae or Rhizopus arrhizus The barley starch is hydrolyzed to glucose and the protein content increases as the fungus grows Expensive SINGLE CELL PROTEIN j Mycelial Fungi Table Myco- and animal protein: conversion rates in protein formation Producer Starting material Product-protein Total product Cow Pig Chicken Fusarium graminearum 1 1 14 g 41 g 49 g 136 g 68 g beef 200 g pork 240 g meat 1080 g wet cell mass kg feed kg feed kg feed kg carbohydrate þ inorganic N sterilization steps are not required at any stage of the process and the product provides an ideal feed for use in pig production Growth Rates of Fungi Although fungi usually grow more slowly than bacteria or yeasts, the data in Table show that, for the practical consideration of biomass production, the growth rates of fungi can be adequate Table Table 417 Composition of Fungi and Nutritional Values The nutritional value of fungal protein has been shown to be very satisfactory and compares well with protein from yeasts and bacteria The compositions of some of the important fungi used for biomass production are shown in Table The distinguishing feature of fungal composition lies in the distribution of the nitrogen content Crude protein values based on total nitrogen  6.25 can be misleading for SCP, because of the RNA content of microbial cells and because fungi have Maximum specific growth rates (mmax) of filamentous fungi used for biomass production Fermentation substrate Fungi Temperature ( C) mmax (hÀ1) Cassava Carob extract Corn stover Glucose Carob extract Not stated Whisky distillery spent wash Sulfite liquor Milk whey Starch hydrolysate Mung bean whey Not stated Coffee wastes Aspergillus fumigatus 121A Aspergillus niger M1 Chaetomium cellulolyticum Fusarium graminearum Fusarium moniliforme Fusarium sp M4 Geotrichum candidum Paecilomyces variotii Penicillium cyclopium Penicillium notatum-chrysogenum Rhizopus oligosporus Trichoderma album Trichoderma harzianum, Rifai 45 36 37 30 30 35 22 38 28 30 32 28 30 0.11 c 0.16 >0.24 0.28 0.22 0.30 0.385 0.31 0.20 0.20 0.16 c 0.46 0.10 Analysis of fungi for protein production (all values are in % dry weight) Fermentation substrate Culture type (FP) Cassava extract Cassava Ground barley Hydrolyzed potato Hydrolyzed potato Cassava starch Crop residues Glucose Carob extract Glucose Sulfite liquor Hydrolyzed potato b b b b b b c c c ND c b Milk whey Cassava extract Waste paper Fiber board waste water Cassava extract ND c b b b b b Fungi Aspergillus fumigatus 121 Aspergillus fumigatus 121A Aspergillus oryzae CMI 44242 Aspergillus oryzae NRRL 3483 Aspergillus oryzae NRRL 3484 Cephalosporium eichhorniae Chaetomium cellulolyticum Fusarium graminearum CMI 145425 Fusarium moniliforme Fusarium semitectum CMI 135410 Paecilomyces variotii Penicillium notatum-chrysogenum CMI 138291 Penicillium cyclopium Rhizopus chinensis Scytalidium acidophilum Sporotrichum pulverulentum Sporotrichum thermopile Trichoderma album FP, fermentation process; b, batch; c, continuous; ND, no data Crude protein (total N  6.25) True protein nitrogen Nonprotein nitrogen 40 37 39.4 40 39 49.5 45 60 43 48 55 43 31.5 27 30.2 22 25 37.8 ND 42 30 34.5 ND 36 21.3 27 23.4 45 35.9 23.6 54 49 45 43 37 64 38 37 36 30 26 54 RNA Lipid Ash 16.3 ND ND 2.5 ND ND ND 10 3.2 10 ND 12.2 ND ND 2 ND 10 13 ND 1.3 1.6 ND ND ND 9 ND ND ND 29.6 24.5 20 16.2 29.7 16 ND 6.2 ND ND 4–6 ND ND 2.6 10 6.6 6–12 ND ND 3.5 ND 6–9 30 30 28.1 418 SINGLE CELL PROTEIN j Mycelial Fungi substantial amounts of their nitrogen as n-acetylglucosamine in chitin of the cell wall The protein content of the cells is approximately two-thirds of the total nitrogen, whereas RNA accounts for 15% and chitin for 10% The chemical composition of single-cell biomass is not fixed; it varies with the limiting substrate, culture conditions, growth rate, temperature, and pH Biomass is grown for its protein content and therefore is never produced under nitrogen limitation; in consequence, the lipid content of the cells is almost invariably low, because fungal cells tend to synthesize maximum lipid content only under nitrogen limitation SCP Production Method The central operation in SCP production is fermentation, for optimum conversion of substrate to microbial mass (Table 7) Any such operation requires the specification of the medium and the growth conditions, the design and operation of a suitable fermentation vessel and associated control systems, and the separation of the cell mass from the fermentation broth On a commercial scale, SCP invariably is produced in submerged liquid culture Batch or continuous culture Table RNA Reduction Processes To meet the 1976 requirements of Food and Agricultural Organization/World Health Organization PAG (1976) and to limit the ingestion of RNA from nonconventional food sources to g per day, various methods of RNA reduction have been investigated: Alkali extraction lowers the RNA levels of the mycelium Treatment of proteins with alkali can lead to the formation of the dipeptide lysinoalanine, which is undesirable in food materials, and care has to be exercised to prevent this from occurring It was claimed that the use of alkali Fermentative production of fungal protein Carbon and energy source Glucose, citrus press water, orange juice Glucose Malt syrup cane molasses Carob bean extract Coffee waste water Glucose Brewery waste, grain press liquor Brewery waste, trub press liquor Carob bean extract Corn and pea waste Corn and pea waste Soy whey Glucose Cheese whey, corn canning waste, sulfite liquor, pumpkin Canning waste Sulfite waste liquor Cheese whey, corn canning waste a techniques may be used Continuous culture, which offers considerable advantages in terms of overall productivity of the fermentation processes, has been the chosen method of production in commercial SCP systems On a commercial scale, this requires specialized plant, which is able to withstand initial sterilization procedures before each production is run and which has sensors fitted into the vessel to monitor the parameters of the process Specific growth rate (m) or dilution rate ( D: hÀ1) Mycelial yield a g per g substrate Culture densitya (g l) Supplied Used Fermenter Microorganism Temperature ( C) l, 40 l bottle Agaricus blazei Ambient 3.5–7.5 15.2 30 42 20 l fermenter Agaricus campestris 25 27 4.5 5.0–5.5 20 7.2 15.8 44.6 Aspergillus niger A oryzae 30–36 28 3.4 4.0–4.5 m ¼ 0.25 D ¼ 0.037 31.5 45 Boletus edulis Calvatia gigantea 25 25 4.5–5.5 6.0 m ¼ 0.0017 2.5 6.25 25 24.8 25 6.0 27.72 74.9 Fusarium moniliforme Geotrichum spp 30 Ambient 5.5–6.5 3.7 Gliocladium deliquescens Ambient 4.6 3000 l fermenter 5000 gal (18 927 l) tank 300 ml flask 250 ml flask pH 14 l fermenter 37 854 l aeration pool 189 270 l pool (continuous) 18 l fermenter 30 l fermenter 10 l carboy, l Lentinus elodes Morchella crassipes Ambient 25 25 4.6 5.5 6.5 18.93 l carboy 18.93 l carboy 37.85 l carboy M deliciosa M esculenta Ambient Ambient 25 5.0–6.0 6.0 6.5 on dry weight basis; carboy-glass, plastic, or metal round bottles m ¼ 0.18 8.8 0.75–1.0 0.384 1.2 m ¼ 0.12 3.2–3.5 7.5 8.02 1.9 10 7.85 33.6 26 48.6 32.8 65 32 48.1 SINGLE CELL PROTEIN j Mycelial Fungi extraction improved the consistency, color, and odor of Pekilo protein biomass if the alkali was neutralized with acid before washing Care had to be taken to ensure that the pH did not fall below 6.0, as this caused RNA to be reprecipitated on to the biomass and hence increased the RNA level of recovered cells Endogenous enzymic hydrolysis reduces the RNA levels from 9% to less than 2% Heat shock at 64 C inactivates the fungal protease and allows the endogenous RNases to hydrolyze the disrupted ribosomal RNA Recovery of Biomass from Culture Broths One of the major advantages possessed by the filamentous fungi over single-celled organisms is the ease with which the former can be separated from the culture medium On a small scale, filtration using filter paper and Buchner funnels usually is adequate For larger volumes, a low-speed, perforated-bowl centrifuge gives good results On a large scale, rotary vacuum filters are the method of choice; nylon filter cloths of suitable retentivity can normally recover >99.9% of biomass mycelium and provision may be made for spray washing as part of the filtration operation; biomass removal is done by scraper blade With a vacuum of 60–65 cm Hg, filtration rates of around 70–80 kg mÀ2 hÀ1 from a medium containing 20% total solids are achievable To reduce subsequent costs of drying if required, various dewatering equipment can further reduce the 80% water content of filter cake Continuous screw expellers of the type used in the brewing industry for dewatering spent grains can be used High-volume throughput necessitates continuous equipment In the Pekilo process, mechanical dewatering produces a material of 35–45% total solids Drying Fungal biomass is easy to dry because its structure does not tend to collapse and lead to case hardening, as does bacterial biomass Using a continuous band drier with single-pass warmair downflow, an air temperature of 75 C is optimal for drying a Penicillium mycelium ex-vacuum filter at 20% solids; a residence time of 20–30 produces a product of 8–10% moisture Heating at too high a temperature reduces the nutritional value of the product because of alteration in lysine availability Other forms of simple driers such as rotary drum driers are also applicable General Product Specifications for SCP as Human Food Important aspects of the product quality of SCP include the following: l Nutritional value Safety l Production of functional protein concentrates l 419 Digestibility (D ) D is the percentage of total nitrogen consumed that is absorbed from the alimentary tract The total quantity of microbial protein ingested by animals is measured and the nitrogen content (I) is analyzed Over the same period, feces and urine are collected, and fecal nitrogen content (F) and urinary nitrogen content (U) are measured Thus D ¼ IÀF  100 U Biological Value (BV) BV is the percentage of total nitrogen assimilated that is retained by the body, taking into account the simultaneous loss of endogenous nitrogen through urinary excretion Thus BV ¼ I À ðF þ UÞ Â 100: IÀF Protein Efficiency Ratio (PER) PER is the proportion of nitrogen retained by animals fed the test protein compared with that retained when a reference protein, such as egg albumin, is fed Preservation of Mycoprotein Preservation is by freezing or chill storage Testing mycoprotein for nutritive value and safety has been extensive and in 1985 resulted in permission being granted by the Ministry of Agriculture, Fisheries and Food for free sale of mycoprotein in the United Kingdom Commercial Production of Mycelial Protein Pekilo Process Pekilo is a fungal protein product produced by fermentation of carbohydrates derived from spent sulfite liquor, molasses, whey, waste fruits, and wood or agricultural hydrolysates It has a good amino acid composition and is rich in vitamins Extensive animal feeding test programs showed that Pekilo protein is a good protein source in the diet of pigs, calves, broilers, chickens, and laying hens Pekilo protein is produced by a continuous fermentation process The organism, Paecilomyces variotii, a filamentous fungus, gives a good fibrous structure to the final product The first plant was installed at the Jamsankoski pulp mill in central Finland in 1973 As an animal feed component, Pekilo protein is comparable to fodder yeast, which is also produced by fermenting spent sulfite liquor Mycoprotein Production In the UK Rank-Hovis-McDougall, in conjunction with Imperial Chemical Industries (ICI) (in 1993, ICI demerged into Zeneca and became the new ICI) commercially 420 SINGLE CELL PROTEIN j Mycelial Fungi Table History of commercial mycoprotein 1965 1967 1969 1975 1985 1986 1990 1992 1996 1997 1998 The search is started for mycoprotein foods by Rank-Hovis-McDougall with ICI The microorganism used for production of mycoprotein is identified as Fusarium graminearum Initial work is begun into flavor and texture of mycoprotein Pilot development production facility is set up Ministry of agriculture, fisheries and food acceptance in the United Kingdom Marlow Foods formed The Quorn brand name launched First ever mycoprotein retail product – a vegetable pie First home-cooking product launched: Quorn pieces First European launch in Benelux countries Mycoprotein products launched in Switzerland Product range exceeds 50 items in UK supermarkets Expansion of product range in the United Kingdom and Europe Development in other countries Available in markets of the United Kingdom, Belgium, Switzerland, the Netherlands, and Ireland Mycoprotein products launched in the United States Mycoprotein products launched in France McDonald’s introduced a Quorn-branded burger bearing the seal of approval of the vegetarian society Quorn replaced around 60% of the meat products in UK food market by their products based on mycoprotein Mycoprotein products available in stores in the United Kingdom, Spain, Belgium, Sweden, the Netherlands, the United States, Switzerland, and the Republic of Ireland Mycoprotein products launched in Australia Quorn foods launched a ‘vegan burger’ into the US market 2002 2003 2004 2005 2006 2010 2011 Table Commercial food products made from mycoprotein which are available in the UK supermarkets Chilled products Deli products Ready meals Frozen products Q pieces, Q mince, Q nuggets, Q chilled sausages, peppered Q steak, crunchy Q fillets garlic and herb, lemon and black pepper crisp crumb Q fillets, Q oriental fillets, Q steak Diane, Q lamb-flavor grills, Q en crûte, Q fillets, Q creatives Thai, Q creatives Italian, Q bolognese, Q fillets in a tomato, red wine, and mushroom sauce, Q fillets in white wine and mushroom sauce, Q BBQ burger, tikka pieces, Q salmon style dill crispbakes, Q tuna style melt, fish less fingers, tuna style and sweet corn crispbake, sizzling BBQ bangers, sizzling burger, sweet and sour crispy bites Roast beef-style, smoked chicken-style, honey roast ham-style, garlic sausages-style, turkey flavor with stuffing, new Q rashers, bacon style, wafer thin ham style, chicken style, smoky ham style slices, roast chicken style slices, ham style, smoky bacon style slices, peppered beef style slices, turkey style with stuffing Q lasagna, Q tikka masala, Q oriental stir fry, Q cottage pie, Q mushroom pie, Q korma, Q spicy light bites, Q roasted light bites, sundried tomato topped fillet, spaghetti and balls, lasagne, sweet and sour, Q mini savory eggs, lamb style grills, breaded goujons, crispy chicken style nuggets, Swedish style balls, Q satay skewers Q burgers, Q quarter pounders, Q premium burgers, Q southern-style burgers, Q sausages, Q pieces, Q mince, new Q dippers, new Q lasagne, new Q chili, fillets in tomato and olive sauce, Q chicken style pieces, Q barbeque slices fillets, Q tikka slices fillets, sausage lattice Q, Quorn brand name marketed another fungal protein, mycoprotein (Quorn), derived from the growth of a Fusarium fungus on simple food-grade carbohydrates Unlike almost all other forms of SCP, mycoprotein is produced for human consumption Sterilized nutrients and minerals Fermenter Chillers Technical Development of Mycoprotein and Quorn Marlow Foods, based in the United Kingdom, is involved in the development, production, and marketing of a range of Quorn consumer food products made with mycoprotein Marlow Foods is a subsidiary of Zeneca Group PLC Mycoprotein is the generic name of the major raw material used in the manufacture of Quorn products It is composed of RNA reduced cells of the Fusarium species (Schwabe) ATCC 20334, grown under axenic conditions in a continuous fermentation process Table shows the history of the development of commercial Quorn mycoprotein Quorn, the brand name of a range of meat-alternative products using mycoprotein as the principal component (Table 9), is Mycoprotein Centrifuge Services e.g., water Figure Heat transfer Schematic of the mycoprotein fermentation process SINGLE CELL PROTEIN j Mycelial Fungi registered to Marlow Foods These products are sold throughout the United Kingdom and increasingly in western Europe Quorn products are a good source of protein, are lower in calorific value (89 kcal per 100 g), and have a higher dietary fiber content than their natural meat equivalents They contain no animal fats or cholesterol and have a high level of dietary fiber They can be eaten by anyone, although they are not recommended for very young children because of their low energy density Quorn products have a tender texture similar to that of lean meat This makes them attractive to vegetarians who miss the taste of meat, as well as to consumers who are reducing their red meat intake The cells are grown by continuous aerobic fermentation (Figure 1) for periods up to 1000 h of continuous operation The plant is sterilized between operating runs by the use of steam under pressure The substrate, glucose syrup, and all the nutrients added to the fermenter are sterile and of food or reagent-grade quality The water is purified before it is used in the fermenter The pH in the fermenter is controlled by the injection of ammonia, which also provides part of the nitrogen source for the cells A continuous spill from the fermenter carries away the biomass produced: The flow rate is such that the volume of the fermenter is displaced every 5–6 h The cell suspension is then taken to a continuously stirred tank reactor held at approximately 65 C, to reduce the RNA content (dry weight) from 10% to less than 2% The suspension is then heated to 90 C, and dewatered by centrifugation before being cooled The harvested cells, collectively known as mycoprotein, are pastelike in consistency and contain around 75% moisture Commercial Production of Mycoprotein Food Products The harvested cells have a similar morphology to animal muscle cells – they are filamentous with a high length–diameter ratio, length 400–700 mm, diameter 3–5 mm, and branch frequency per 250–300 mm (Figure 2) The product assembly process seeks to reproduce the structural organization that exists in natural meats In meat, muscle cells are held together by connective tissue To establish a similar product texture in Quorn products, the cells are mixed with a protein binder, together with flavoring and other ingredients, depending on the final product format, and then heated (Figure 3) This causes the protein binder to gel and bind the cells together The resultant structure is very meatlike in appearance, texture, and formed products such as steaks or fillets Developing Texture The ingredients added differ according to the product produced The mixture is transported to a forming machine, set up for the product being produced For Quorn pieces and mince the forming machine produces strips of Quorn, which then are reduced in size The next step is to steam the mixture The high temperatures reached during steaming affect gelation of the albumen, which is added at the mixing stage; this in turn improves the texture of the product by increasing firmness Figure 421 Micrograph of mycoprotein illustrating its filamentous nature After steaming, the products are cooled rapidly, before weighing, packing, and storage Characteristics of Mycoprotein Products Good Source of Dietary Fiber Because Quorn food products contain 60–90% of mycoprotein, there will be a corresponding significant dietary fiber content in the final product Mycoprotein contains 5.1 g dietary fiber per 85 g (Table 10) Fiber includes 65% b-glucans and 35% chitin, and, of this, 88% is insoluble and 12% soluble No Interference with Mineral Absorption Quorn products not contain phytic acid or phytic salts that may interfere with mineral absorption No significant effect on the absorption of calcium, magnesium, phosphorus, zinc, or iron has been shown in comparison with a polysaccharidefree diet Lower in Fat, Saturated Fat, and Cholesterol than Equivalent Meat Products Mycoprotein contains only 2.6 g fat and 0.5 g saturated fat per 85 g (Table 10) It does not contain any trans fatty acids (Table 11) Quorn products, however, may contain slightly higher levels of fat and some trans fatty acids, as small 422 SINGLE CELL PROTEIN j Mycelial Fungi Steaming Mixing Forming Mycoprotein Ingredients Metal detection Weigh and bag Chilling Texturizing Cutting (if required) Shrink wrap Distribution for sale Boxing Deep freeze hold Figure Table 10 Schematic of the manufacturing process for Quorn products Nutrition comparison: mycoprotein compared with other sources of dietary protein Food type Mycoprotein Cheddar cheese Whole eggs Ground beef: regular, medium baked Chicken: light meat, roasted Fish: cod raw Soy flour: raw, full fat Chickpeas: mature seeds, raw Pigeon peas: mature seeds, raw Table 11 100 g) Fatty acid Cold store Energy (kcal) Protein (g) Total carbohydrate (g) Dietary fiber (g) Total fat (g) Cholesterol Saturated Mono Poly (mg) 85 30 50 85 72 120 75 245 9.4 7.5 6.3 19.6 7.7 0.38 0.6 5.1 0 2.6 10 17.8 0.6 6.3 1.6 0.4 2.8 1.9 7.8 1.6 0.28 0.68 0.66 32 212 74 85 85 30 100 100 130 89 131 364 343 23.1 19.4 10.4 19.30 21.70 0 10.6 60.65 62.78 0 2.9 17.4 15.0 3.5 0.7 6.2 6.04 1.49 0.9 0.1 0.9 – – 1.3 0.1 1.4 – – 0.8 0.25 3.5 – – 64 47 0 Fatty acid profile of mycoprotein (fat content ¼ g per Grams per 100 g fat in mycoprotein C16:Palmitic 9.3 C18:0 Stearic 2.0 C18:1 Oleic 9.6 C18:2 Linoleic 29.8 C18:3 a13.5 Linolenic Fat breakdown (g) Measure (g) Grams per 100 g mycoprotein 0.3 0.1 0.3 1.0 0.4 amounts of fat may be added to enhance the taste and texture These products contain between 2.4 and 8.4 g fat and 0.4– 2.4 g saturated fat per 85 g cooked weight In comparison, equivalent meat products contain 2.5–3.5 times more fat and saturated fat Rich in Protein Content Quorn products typically contain between 10 and 13 g of protein per 85 g serving, most of which comes from mycoprotein Small amounts come from egg albumen and milk proteins, which are added in the manufacturing process The SINGLE CELL PROTEIN j Mycelial Fungi Table 12 423 Protein, fat, and calorie content of selected commercial mycoprotein food products compared to meat equivalents Food (per 100 g cooked portion) Protein (g) Carbohydrate (g) Total fat (g) Saturated fat (g) Calories (kcal) Energy density (kcal) Quorn salmon-style dill crispbakes Quorn tuna-style melt Fish-less fingers Tuna style and sweet corn crispbake Sizzling burgers Sizzling BBQ bangers Quorn sausages Mince Sundried tomato-topped fillet Sausages and mash Cottage pie Spaghetti and balls Lasagne Sweet and sour Roast-style sliced fillets Cornish style pasties Deli bacon style Quorn barbeque-sliced fillets Quorn tikka-sliced fillets Deli chicken style Peppered beef-style slices Quorn red leicester and onion sausages Southern style burgers Quorn cottage pie 7.0 12.0 10.0 6.6 18.0 12.0 12.6 14.5 12.5 4.6 2.5 4.3 4.8 3.7 15.5 7.0 11.8 13.0 12.0 16.3 14.5 15.0 10.7 2.5 22.0 18.0 22.0 22.0 7.0 9.5 11.6 4.5 6.5 9.5 11.0 11.9 12.5 17.0 3.5 31.0 3.0 8.0 9.0 4.5 7.6 10.0 14.5 9.0 6.6 12.0 10.5 6.2 6.0 11.0 6.8 2.0 5.7 2.3 1.0 0.8 2.7 4.0 6.0 12.0 15.5 1.0 1.5 2.6 2.1 6.5 9.8 1.4 1.0 4.3 1.8 1.0 3.0 5.0 0.6 0.5 2.6 0.8 0.5 0.2 1.2 0.6 1.0 5.0 1.5 0.3 0.6 0.7 1.0 4.0 1.2 0.9 182 234 233 176 154 195 165 94 135 83 67 76 97 93 141 260 199 93 98 107 107 167 189 59 1.82 2.34 2.33 1.76 1.54 1.95 1.65 0.94 1.35 0.83 0.67 0.76 0.97 0.93 1.41 2.60 1.99 0.93 0.98 1.07 1.07 1.67 1.89 0.59 Table 13 Essential amino acid content of mycoprotein compared with other foods that contain protein (g amino acids per 100 g edible portion) Essential amino acids Mycoprotein Cow’s milk a Egg b Beef c Soybeans d Peanuts e Wheat f Chicken g Histidine Isoleucine Leucine Lysine Methionine Phenylalanine Tryptophan Threonine Valine 0.39 0.57 0.95 0.91 0.23 0.54 0.18 0.61 0.6 0.09 0.20 0.32 0.26 0.08 0.16 0.05 0.15 0.22 0.3 0.68 1.1 0.90 0.39 0.66 0.16 0.6 0.76 0.66 0.87 1.53 1.6 0.5 0.76 0.22 0.84 0.94 0.98 1.77 2.97 2.4 0.49 1.91 0.53 1.59 1.82 0.65 0.91 1.67 0.92 0.32 1.3 0.25 0.88 1.08 0.32 0.53 0.93 0.30 0.22 0.68 0.18 0.37 0.59 0.63 1.07 1.59 1.76 0.58 0.85 0.24 0.91 1.06 Whole fluid milk (3.3% fat) Raw fresh egg c Ground beef (regular, medium baked) d Mature raw soybeans e Raw peanuts (all types) f Durum wheat g Chicken, broilers or fryers, back, meat and skin, cooked, stewed Source: U.S Department of Agriculture Nutrient Data Base for Standard Reference, 12 March 1998 a b nutritional advantages of Quorn products (Table 12) include the fact that they are excellent sources of high-quality protein but are significantly lower in fat, saturated fat, and calories than many protein foods High-Quality Protein Dietary proteins contain a mixture of 20 amino acids, all of which are necessary to support growth Although most amino acids can be made in the body, nine essential amino acids must be supplied by the diet: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine The quality of a dietary protein is based on its content of essential amino acids Table 13 compares the amino acid content of mycoprotein with other commonly consumed protein foods The PER for mycoprotein is 2.4, BV 84, and D 78 A recent development in the United States required by the Food and Drug Administration is that the protein digestibility-corrected 424 SINGLE CELL PROTEIN j Mycelial Fungi Table 15 Vitamin and mineral comparison: mycoprotein compared with other sources of dietary protein Food type Mycoprotein Cheddar cheese Whole eggs Ground beef: regular, medium baked Chicken: light meat, roasted Fish: cod raw Soy flour: raw, full fat Peanut flour: defatted Wheat flour: whole grain Measure Ca Fe Mg P K Na Zn Vitamin A Thiamin Riboflavin Niacin (g) (mg) (mg) (mg) (mg) (mg) (mg) (mg) (mg) (mg) (mg) (mg) Vitamin B6 Folic acid Vitamin C (mg) (mg) (mg) 85 30 50 85 38 216 25 8.5 0.5 0.2 0.7 2.1 85 11 0.92 19.6 185 201 43 85 30 100 100 11.9 62 140 34 0.42 1.9 2.10 3.60 207 755 1290 363 38 8.3 12.8 35.7 129 370 137 215 154 89 116.5 117 148 760 357 85 30 61 188 186 63 51 66 180 8.5 0.9 0.6 4.2 83RE 95RE 0.01 0.01 0.03 0.03 0.2 0.1 0.25 0.136 0.3 0.02 0.04 0.1 0.02 0.07 0.2 0.1 5.5 0.24 7.7 0 0 0.66 7RE 0.05 0.08 8.9 0.46 2.6 0.49 1.0 5.10 2.60 0.08 17 0.700 0.502 0.07 0.35 0.480 0.165 2.1 1.3 27.0 4.957 0.24 0.14 0.50 0.407 6.9 104 0 0.9 0 12RE 4RE 0 RE, retinal equivalent Table 14 Protein digestibility corrected amino acid score (PDCAAS) of selected food proteins Protein source PDCAAS Data source Quorn pieces Casein Egg white Chicken (light meat: roasted)trun -1 Turkey (minced: cooked) Fish (cod: dry cooked)trun -1 Soybean protein Beef Mycoprotein Pea flour Kidney beans (canned) Rolled oats Lentils (canned) Peanut meal Whole wheat Wheat gluten 1.0 1.0 1.0 1.0 0.97 0.96 0.94 0.92 0.91 0.69 0.68 0.57 0.52 0.52 0.40 0.25 d a a c c c b a d a a a a a a a a: Food and Agriculture Organization/World Health Organization Joint Report (1989) b: Sarwar and McDonough (1990) c: Calculated from amino acid data in the US Department of Agriculture Data Base for Standard Reference, 12 March 1998 (assumes a digestibility equivalent to beef ¼ 94%) d: Calculated from Marlow Foods data amino acid scoring (PDCAAS) method must be used for most nutrition labeling purposes This method takes into account the food protein’s essential amino acid profile, its digestibility, and its ability to supply essential amino acids in amounts required by humans It compares the essential amino acid profile of a food, corrected for digestibility, to the Food and Agricultural Organization/World Health Organization 2- to 5-year-old essential amino acid requirement pattern The 2- to 5-year-old pattern is used because it is the most demanding pattern of any age-group other than infants The PDCAAS for mycoprotein is 0.91, based on a digestibility factor of 78% for mycoprotein Table 14 shows how mycoprotein compares with the PDCAAS of other food proteins Mineral and Vitamin Composition Mycoprotein used in Quorn products compares well in mineral and vitamin composition with other sources of dietary protein (Table 15) The PDCAAS value for Quorn products (which all contain egg albumin) is See also: Aspergillus: Aspergillus oryzae; Fermentation (Industrial): Production of Oils and Fatty Acids; Mycotoxins: Classification Further Reading Anke, T (Ed.), 1997 Fungal Biotechnology Chapman & Hall, London Atkinson, B., Mavituna, F., 1991 Biochemical Engineering and Biotechnology Handbook, second ed Macmillan, New York Denny, A., Aisbitt, B., Lunn, J., 2008 Mycoprotein and health British Nutrition Foundation Nutrition Bulletin 33, 298–310 Higgins, I.J., Best, D.J., Jones, J (Eds.), 1988 Biotechnology Principles and Applications Blackwell Scientific Publications, Oxford Khan, M., Khan, S.S., Ahmed, Z., Tanveer, A., 2009 Production of fungal single cell protein using Rhizopus oligosporus grown on fruit wastes Biological Forum (2), 32–35 PAG Ad Hoc, 1976 Working group meeting on clinical evaluation and acceptable nucleic acid levels of SCP for human consumption PAG Bulletin (3), 17–26 Sarwar, G., McDonough, F.E.C., 1990 Journal of the Association of Official Analytical Chemists 73, 347–356 Smith, J.E., 1996 Biotechnology, third ed Cambridge University Press, Cambridge Solomon, G.L., 1985 Production of filamentous fungi In: Moo-Young, M (Ed.), Comprehensive Biotechnology, vol Pergamon Press, Oxford Wainwright, M., 1992 Fungi in the Food Industry An Introduction to Fungal Biotechnology John Wiley, Chichester Relevant Website http://www.quorn.co.uk/ – Quorn