terça-feira, 21 de julho de 2015
Indústria: café, chá, cacau, mandioca e macaxeira
Já fiz algumas reclamações sobre a ideologia industrializante, em especial no progressista (em outros tempos...) município de Sant'Anna do Livramentto: melhor seria um supermercado que uma fábrica de aviões a jato. E depois comecei a falar nos importadores por atacado de café na Europa e suas redes de distribuição de varejo. E pensei que isto é que o Brasil deveria ter feito, se não em 1929, pelo menos em 2014 ou 2013, indo de volta até 1929... E será que, se houvesse um capital humano e social decente neste país, não teríamos sido nós a inventar a rede Starbuck? E outra rede? Daqui a 100 anos? Não pode? Ou o que não pode é criar capital humano, que gera social, que gera democracia?
Então segui pensando no cacau: distribuição internacional? Caminhões, vans, kombis, motos, brasileirinhos vendendo de porta em porta? Associações como as assim erigidas maisons du chocolat, ou como quer que viessem a ser chamadas? Mon pote de chocolat? E os insumos, a produção de tratores, a hoje chamada bioengenharia, a antiga revolução verde, a verde-amarela?
E a mandioca? Sua árvore de produtos é uma das peças de informação mais impressionantes que vi em meus vários anos de carreira como professor de economia política.
Parece óbvia a razão que impede o verdadeiro desenvolvimento do agronegócio e a perseguição de reindustrialização com base em crendices, ideologia e fatos distorcidos, além de algumas obviedades que não devem ser tomadas como especiais virtudes, mas obviedades contábeis (como, por exemplo, dizer que as outras indústrias geram mais renda e emprego). Trata-se da revolução que iria ocorrer, deveria ser feita no campo, acabando com a estrutura agrária feudal de boa parte do Brasil. Ou seja, sem terras para produção em massa em pequena escala, o poder feudal iria esboroar-se.
Isto que não falei na produção de tratores, de aviões agropecuários, de satélites de controle de ventos, de pilhas de coisas que poderiam ter feito do Brasil um verdadeiro país agrícola. Aquela tolice de aumentar os linkages artificialmente seria substituída por elevação deles por meio de operações econômicas sólidas, baseadas na exploração inaudita das vantagens comparativas do país das águas e das três safras anuais. Então peguei daqui a lista de derivados industriais da mandioca:
Nonfood uses Starch makes a good natural adhesive. There are two types of adhesives made of starches, modified starches and dextrins: roll-dried adhesives and liquid adhesives.
The application of cassava in adhesives continues to be one of the most important end uses of the product. In the manufacture of glue the starch is simply gelatinized in hot water or with the help of chemicals. For conversion into dextrin it is subjected separately or simultaneously to the disintegrative action of chemicals, heat and enzymes.
In gelatinized starch adhesives, quality requirements are such that the medium-quality flours can be used. In dextrin manufacture, the demands are much more exacting: only the purest flours with a low acid factor are acceptable. Cassava dextrin is preferred in remoistening gums for stamps, envelope flaps and so on because of its adhesive properties and its agreeable taste and odour.
Dextrins were accidentally discovered in 1821 when during a fire in a Dublin (Ireland) textile mill one of the workmen noticed that some of the starch had turned brown with the heat and dissolved easily in water to form a thick adhesive paste.
Three primary groups of dextrins are now known: British gums, white dextrins and yellow dextrins.
British gums are formed by heating the starch alone or in the presence of small amounts of alkaline buffer salts to a temperature range of about 180°220°C. The final products range in colour from light to very dark brown. They give aqueous solutions with lower viscosities than starch.
White dextrins are prepared by mild heating of the starch with a relatively large amount of added catalyst, such as hydrochloric acid, at a low temperature of 80º-120°C for short periods of time. The final product is almost white, has very limited solubility in water and retains to varying degrees the set-back tendency of the original starch paste.
Yellow dextrins are formed when lower acid or catalyst levels are used with higher temperatures of conversion (150°-220°C) for longer conversion times. They are soluble in water, form solutions of low viscosity and are light yellow to brown in colour.
The following are some of the major uses of dextrins in nonfood industries.
Corrugated cardboard manufacture. One of the large users of dextrins is the corrugated cardboard industry for the manufacture of cartons. boxes and other packing materials. The layers of board are glued together with a suspension of raw starch in a solution of the gelatinized form. The board is pressed between hot rollers, which effects a gelatinization of the raw starch and results in a very strong bonding. Medium-quality flours are suitable for this purpose provided the pulp content is not too high.
Remoistening gums. These adhesives are coated and dried on surfaces, such as postage stamps and envelope flaps, for moistening by the user before application to another surface. Cassava dextrins in aqueous solution are well suited for this purpose as they give a high solids solution with clean machining properties.
Wallpaper and other home uses. Various types of starch-based products are used as adhesives for wallpaper and other domestic uses.
Foundry. Starch is used as an adhesive for coating the sand grains and binding them together in making cores which are placed in moulds in the manufacture of castings for metals.
Well drilling. Starches and modified starches mixed with clay are used to give the correct viscosity and water-holding capacity in bores for the exploratory drilling of oil wells or water wells. These starch products are replacing other commercial products for making the muddy materials which are indispensable for drilling wells. For this purpose a coldwater-soluble pregelatinized starch which can be made up to a paste of the required concentration on the spot is desired.
Paper industry. In the paper and board industries, starch is used in large quantities at three points during the process:
(i) at the end of the wet treatment, when the basic cellulose fibre is beaten to the desired pulp in order to increase the strength of the finished paper and to impart body and resistance to scuffing and folding;
(ii) at the size press, when the paper sheet or board has been formed and partially dried, starch (generally oxidized or modified) is usually added to one or both sides of the paper sheet or board to improve the finish, appearance, strength and printing properties;
(iii) in the coating operation, when a pigment coating is required for the paper, starch acts as a coating agent and as an adhesive.
Cassava starch has been widely used as a tub size and beater size in the manufacture of paper, in the past mainly on account of its low price. A high colour (whiteness), low dirt and fibre content, and, above all, uniformity of lots are needed in this instance.
An important new application of starch is in the machine-coating of magazine paper, formerly done exclusively with caseins. There are indications that cassava is particularly well suited to the purpose; however, definite specifications for the starch still have to be worked out.
Textile industry. In the textile industry, starches occupy an important place in such operations as warp sizing, cloth finishing and printing. Warp sizing is the application of a protective coating to prevent the single yarns from disintegrating during weaving. The size consists of an adhesive and a lubricant and is generally removed after weaving. Cloth finishing alters the "feel" of the fabric by making it firmer, stiffer and heavier. Cassava starch is also used for cloth printing or producing certain designs in various colours on the smooth surface of a finished fabric. While cassava accounted for about 20 percent of all starch for these purposes in 1937, it has been largely replaced by other starches after the Second World War.
An exception is the manufacture of felt, where cassava continues to be used exclusively in the finishing process.
Wood furniture. Before the Second World War the manufacture of plywood and veneer relied mainly on cassava as a glue. The basic material in this case is gelatinized at room temperature with about double the amount of a solution of sodium hydroxide. After prolonged kneading of the very stiff paste in order to give it the required stringy consistency, the glue is applied to the wood with rollers. As the presence of a certain amount of the pulp is useful, medium- to low-quality flours are acceptable or even preferable, although the presence of sand is objectionable.
Since 1945, however, the use of cassava as a glue has declined to second place owing to the increasing success of water-resistant plastics.
Particle board from cassava stalks
As cassava cultivation increases, more stalks will become available for disposal. The Tropical Products Institute, London, has been working on the utilization of the cassava plant. Particle boards could be made from cassava stalks by cutting them into small sections and mixing them with certain resins. The strength of the board can be varied by altering the resin content or the density.
Cassava is one of the richest fermentable substances for the production of alcohol. The fresh roots contain about 30 percent starch and 5 percent sugars, and the dried roots contain about 80 percent fermentable substances which are equivalent to rice as a source of alcohol.
Ethyl alcohol is produced from many carbohydrate materials. In Malaysia and some other countries, many factories are equipped to use cassava roots, starch or molasses (by-product of the sugar industry), the type of product depending on the costs of the raw materials. When cassava is used, the roots are washed, crushed into a thin pulp and then screened. Saccharification is carried out by adding sulfuric acid to the pulp in pressure cookers until total sugars reach 15-17 percent of the contents. The pH value is adjusted by using sodium carbonate, and then yeast fermentation is allowed for three to four days at a suitable temperature for the production of alcohol, carbon dioxide and small amounts of other substances from sugar. Alcohol is then separated by heat distillation. The yield of conversion is about 70-110 litres of absolute alcohol per ton of cassava roots depending on the variety and method of manufacture. The crude alcohol of cassava is described as average in quality. It has a disagreeable odour, but can be improved if the first and last fractions in the distillation process are discarded. It is usually utilized for industrial purposes, as in cosmetics, solvents and pharmaceutical products. If the production is required for human consumption, special care should be taken in handling the roots to rid them of hydrocyanic acid.
Microbial protein is attracting growing interest owing to the enormous protein requirements of the world. Among the microorganisms which are considered possible food sources, yeast has perhaps stirred the greatest interest. Candida and saccharomyces yeasts have had a well-established place for many years as feed, and the technology of production, the composition and the nutritive value of yeast are well known.
Most of the production of yeast is based on such low-cost raw materials as waste liquids, wood hydrolyzates and molasses. Starch-rich plant materials from wastes or surplus production are also utilized as substrata for yeast production. Cassava starch and cassava roots are being used in Malaysia and some other countries for the production of yeasts for animal feed' the human diet and for bakery yeast. The starch is hydrolyzed into simple sugars (predominantly glucose) by means of mineral acid or by enzymes. Certain yeasts are then propagated which assimilate the simple sugars and produce microbial cellular substances. The dry, inactive yeast contains about 7 percent moisture and the raw protein content can vary between 40 and 50 percent depending on the raw material.
The yield of yeast production also depends on the raw material. In some applications of cassava starch conversion into substances obtained from yeasts, a 38-42 percent yield of yeast product containing 50 percent raw protein has been obtained.