Crystallization of fats is a determinant physical event affecting the structure and properties of fat-based products. The stability of these processed foods is regulated by changes in the physical state of fats and alterations in their crystallization behavior. Problems like polymorphic transitions, oil migration, fat bloom development, slow crystallization and formation of crystalline aggregates stand out. The change of the crystallization behavior of lipid systems has been a strategic issue for the processing of foods, aiming at taylor made products, reducing costs, improving quality, and increasing the applicability and stability of different industrial fats. In this connection, advances in understanding the complex mechanisms that govern fat crystallization led to the development of strategies in order to modulate the conventional processes of fat structuration, based on the use of crystallization modifiers. Different components have been evaluated, such as specific triacyglycerols, partial glycerides (monoacylglycerols and diacylglycerols), free fatty acids, phospholipids and emulsifiers. The knowledge and expertise on the influence of these specific additives or minor lipids on the crystallization behavior of fat systems represents a focus of current interest for the industrial processing of oils and fats. This article presents a comprehensive review on the use of crystallization modifiers in lipid systems, especially for palm oil, cocoa butter and general purpose fats, highlighting: i) the removal, addition or fractionation of minor lipids in fat bases; ii) the use of nucleating agents to modify the crystallization process; iii) control of crystallization in lipid bases by using emulsifiers. The addition of these components into lipid systems is discussed in relation to the phenomena of nucleation, crystal growth, morphology, thermal behavior and polymorphism, with the intention of providing the reader with a complete panorama of the associated mechanisms with crystallization of fats and oils.

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Chemical interesterification of different lipid materials has considerable potential for the production of a wide variety of special fats with improved functional and nutritional properties. The present study aimed to evaluate the chemical interesterification of blends of high‐oleic sunflower oil (HOSO) and fully hydrogenated palm oil (FHPO) in the ratios (% w/w) of 80:20, 70:30, 60:40 and 50:50. The blends were characterized in triacylglycerol composition, melting point, solid fat content and crystallization behavior, and some applications in food products were suggested. The interesterification altered the solid fat content, melting point and crystallization isotherm of the samples, after the levels of trisaturated triacylglycerols decreased and disaturated–monounsaturated and monosaturated–diunsaturated triacylglycerol contents increased, due to the randomization of fatty acids. The modification in the triacylglycerol composition promoted greater miscibility between the HOSO and FHPO fractions, creating new application possibilities for the food industry.

The crystallization behavior of cocoa butter (CB) is the essential structuration issue in the development of chocolate products. An alternative to modify and control the crystallization patterns of CB in chocolate production is the incorporation of specific emulsifiers in their formulations. In this work, the effects of sorbitan monostearate (SMS) and sorbitan monooleate (SMO) in the crystallization and consistency behaviors as well as on the microstructure of CB were evaluated. CB samples at three different concentrations (0.5, 1.0 and 1.5 % w/w) of SMS and SMO were prepared and their main physical–chemical attributes determined. CB added with 1.5 % of SMS showed the largest effects with a sharp increase in the onset of the crystallization temperature (from 19.3 to 23.8 °C) and doubling the yield value (consistency) of pure cocoa butter. The classic two‐step isothermal crystallization behavior and morphology of CB were also modified with the addition of SMS. A possible explanation based on the solubility of SMS in an organic medium and its ability of self‐assembling was suggested as a mechanism for SMS performance in CB. SMS was considered as a potential crystal modifier for CB by changing its crystal structure and enhancing its thermal resistance—factors that favor the use of this emulsifier in the production of improved thermally stable chocolates.

Recebido em 27/3/07; aceito em 11/10/07; publicado na web em 2/4/08 QUANTIFICATION OF TBHQ (TERC BUTYL HYDROQUINONE) AND OXIDATIVE STABILITY EVALUATION OF COMMERCIAL SUNFLOWER OILS. Sunflower oil is one of the vegetable oils most susceptible to oxidative reaction. Therefore the presence of natural (tocopherol) and/or synthetic (TBHQ) antioxidants is a prerequisite to secure the stability of this oil during its shelf life, especially with the increased use of PET packaging. On determining the total tocopherol content in 10 samples of deodorized sunflower oils, high losses in total tocopherol during deodorization were identified. In order to facilitate researche involving oxidative stability of vegetable oils, a method for isolated quantification of TBHQ using the isocratic elution system was developed.Keywords: sunflower oil; oxidative stability; TBHQ. INTRODUÇÃOÓleos vegetais são importantes fontes de energia e de ácidos graxos essenciais (principalmente ácido linoléico -ω-6). Além disso, são importantes também para o funcionamento regular do organismo humano, como veículos no transporte das vitaminas lipossolúveis. 1A principal deterioração em óleos é a oxidação. Sabor, aroma e qualidade indesejáveis são algumas das características encontradas em óleos oxidados. 1A composição em ácidos graxos, de maneira geral, não se altera durante as etapas do refino (químico ou físico). Porém, as condições de processamento, principalmente durante a desodorização, como é o caso da temperatura e tempo de retenção, alteram a formação dos isômeros trans no produto final. Sabendo-se que a oxidação de lipídios é uma reação que não pode ser totalmente cessada e que, uma vez iniciada, ocorre em alta velocidade, o seu início pode ser retardado pela adição de antioxidantes. Além disso, para retardar o início da oxidação em óleos vegetais deve-se adotar alguns cuidados no seu processamento, como o uso de equipamentos em aço inox, embalagens herméti-cas, refrigeração e proteção contra raios ultravioletas. 1A estabilidade oxidativa é um dos mais importantes indicadores utilizados para avaliação da qualidade dos óleos comestíveis. 3A diferença da estabilidade entre os diversos tipos de óleos vegetais é decorrente principalmente da presença de ácidos graxos poliinsaturados e da quantidade de γ-e δ-tocoferóis, além da adição de antioxidantes sintéticos.Antioxidantes, presentes naturalmente em óleos vegetais ou adicionados a estes, são substâncias inibidoras da oxidação lipídica, ou seja, ajudam na prevenção da deterioração que ocorre em óleos devido à reação de oxidação, causada por espécies reativas de oxigênio. 1O principal antioxidante natural encontrado em óleos vegetais é o tocoferol, podendo ocorrer em quatro formas diferentes: α-, β-, γ-e δ-tocoferol. Esta substância apresenta alto valor nutricional possuindo atividade antioxidante (principalmente nas formas de γ-e δ-tocoferóis) e poder vitamínico E (em especial nas formas α-e β-tocoferóis). 4O óleo de girassol, devido ao seu alto teor de ácido linoléico, é um dos óleos vegetais mais...