Starch extraction from roots and tubers uses grating with water and sieves to separate the starch slurry from residual mass. The starch is recovered by decantation or centrifugation. The yam starch extraction is difficult due to high viscosity of the slurry caused by non‐starch polysaccharides (NSP). The establishment of an efficient extraction process may turn yam into a competitive raw material. In this paper Dioscorea alata starch extracted by four methods was characterized in order to establish the impact of treatments. When the tubers were digested with an aqueous oxalic acid/ammonium oxalate (OA/AO) 1/1 solution, it was easier to separate the starch slurry from residual mass, because viscosity was reduced. For all the others methods tested, the viscosity remained almost the same. The nitrogen present in yam tubers was removed during the different extractions to a different extent. The largest nitrogen reduction was observed with OA/AO followed by the control (water). The spectrum of starch granules sizes obtained also varied according to the treatment. Results proved that NSP carries small starch granules over to the waste water. The smaller starch granules diameter varied from 1.9 µm (OA/AO extraction) to 13.5 µm (water and pectinase extractions). The larger diameter varied from 41.0 µm (NaOH treatment) to 67.7 µm (OA/AO). All starches extracted showed a RVA behavior in agreement with literature for yam starch, but with small differences due to the influence of methods. OA/AO extraction showed the best recovery (18 g of starch/100 g tuber yam) and granular variation but it interfered with the rheological behavior of starch.

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No Brasil, a falta de competitividade do setor de fécula de mandioca em relação ao amido de milho é explicada pelas dificuldades em obter matéria-prima - raízes de mandioca - em quantidades e preços estáveis. A resolução desses problemas envolve a adoção de arranjos institucionais que estabilizam as transações entre produtores e industriais. A análise de 37 fecularias permitiu avaliar as características das transações e o desempenho dos arranjos adotados, medido por meio da capacidade das empresas em estabilizar seu fornecimento de matéria-prima. Os arranjos institucionais encontrados foram classificados em seis tipos, do mercado até a integração vertical, em função do nível de garantia oferecido para entrega de matéria-prima. Apesar da existência de especificidade dos ativos e de incerteza, as empresas preferem as transações via mercado spot, arranjo identificado como menos eficiente. A incerteza ligada ao funcionamento das instituições aumenta os custos de transação dos arranjos contratuais, o que explica a preferência dos atores pelo mercado. Os acordos contratuais com garantias intermediárias e fortes foram mais eficientes, mas com maiores custos de transação. Os resultados indicam dois caminhos para melhorar a competitividade do setor: (1) melhoria na eficiência do mercado, sistema com menores custos de transação; (2) redução dos custos de transação dos arranjos institucionais com maiores garantias, o que proporcionaria sistemas mais eficientes. Enquanto nenhuma dessas soluções for adotada, as fecularias brasileiras continuarão com arranjos de baixos custos de transação, mas fraco desempenho.
The lack of competitiveness of Brazilian cassava starch industry in relation to corn starch is explained by the difficulty to obtain raw material (cassava roots) in stable quantities and stable prices. The resolution of these problems involves the adoption of governance systems that stabilize the transactions between producers and processing units. The analysis of 37 factories has allowed the evaluation of transaction costs and the performance of adopted governance systems, calculated from the ability to stabilize raw material supply. The governance systems were classified into six groups, from spot market to vertical integration, depending on the level of warranty offered in the delivery of raw material. Despite the identification of asset specificity and transaction risk, cassava starch companies prefer market transaction, a governance system identified as less efficient. The low efficiency of institutions increase transaction costs of contractual governances, which can explain the preference for the market. Contractual agreements with intermediaries and strong warranties are more efficient, but with high transaction costs. These results indicate two ways to improve the competitiveness of the cassava starch industry: (1) improvement in market efficiency, system with lower transaction costs, (2) reduction of transaction costs for governance systems with more warranties, which might generates more efficient systems. ...

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This study sought to identify the relevant factors for collective action in the context of the use of common goods and what factors are influential in the cooperation between individuals. For this, an integrative analysis of 267 articles was carried out, published in the Scopus, Science Direct and Web of Science databases. The results show little progress in the inclusion of new analysis factors and the presented factors do not have linear effects on all collective actions, and advances are necessary for a more complete theory. ResumoEste estudo buscou identificar os fatores relevantes para a ação coletiva no contexto do uso dos bens comuns e quais fatores são influenciadores da cooperação entre indivíduos. Para tanto, foi realizada uma análise integrativa de 267 artigos, publicados nas bases de dados Scopus, Science Direct e Web of Science. Os resultados demonstram poucos avanços na inclusão de novos fatores de análise e os fatores apresentados não possuem efeitos lineares sobre todas as ações coletivas, sendo necessários avanços para uma teoria mais completa. Palavras-chave:Recursos de uso comum. Ação coletiva. Cooperação. Cooperativo.