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Abstract(s)
Os cremes de rosto são produtos funcionais, constituídos por múltiplos ingredientes com diversificadas funções. Tradicionalmente, um dos principais ingredientes são os lípidos que podem ser saturados ou insaturados. Os lípidos insaturados e a sua interação com os restantes componentes dos cremes, bem como fatores externos, permitem prever a ocorrência do processo de oxidação. A oxidação lipídica, por sua vez, é um fenómeno espontâneo e inevitável, e um dos grandes problemas de deterioração de produtos cosméticos, como é o caso dos cremes de rosto, afetando-os quimicamente, fisicamente e sensorialmente. Assim, torna-se importante o estudo do comportamento do produto durante o seu tempo útil de vida, com base em métodos científicos e reprodutíveis. Neste trabalho, foram testados dez cremes de diferentes composições, armazenados em estufa a 30ºC, na ausência de luz, durante seis meses. Ao longo de cada mês, foi retirado um lote de amostras (de A a J), feita a respetiva análise sensorial (verificação de alteração na cor, odor e aspeto) e essas alíquotas foram congeladas para a realização das análises em simultâneo. Para cada amostra de creme, foram determinados os produtos primários de oxidação pelo método dos Dienos Conjugados (DC) expresso em percentagem, e pelo método do Índice de Peróxidos (IP) expresso em meqO2/kg amostra seca. Foram também determinados os produtos secundários de oxidação, recorrendo ao método do Índice de p-Anidisina (ipA) e do ensaio das Substâncias Reativas ao Ácido 2- tiobarbitúrico (TBARS), expresso em concentração de malonaldeído (MDA), (mg/g amostra seca). Inicialmente, conclui-se que a escolha do solvente para a dissolução das amostras não tem influência nos resultados obtidos. Na determinação do IP segundo o método iodométrico e o método colorimétrico, constata-se que ambos apresentam elevada sensibilidade e uma boa correlação entre si, com a vantagem de que o segundo requer menos quantidade de amostra, solvente e menos tempo de análise em laboratório. Conclui-se que o creme que apresenta maior extensão de oxidação lipídica, com base nos resultados obtidos de Valor Total de Oxidação (TOTOX), é o creme J. Já o creme D é o que apresenta uma menor extensão de oxidação lipídica. É de supor que a presença de ácidos gordos saturados permite inibir o processo de oxidação lipídica, diminuindo a velocidade de oxidação. Também, a presença de aditivos, como o tocoferol, que tem a função antioxidante, pode atuar como pro-oxidante.
Skincare products are functional products, consisting of multiple ingredients with several functions. Traditionally, one of the main ingredients are lipids that can be saturated or unsaturated. These unsaturated lipids and their interaction with the other components of the skincare products and external factors allow understanding and predicting the occurrence of oxidation. Lipid oxidation is a spontaneous and inevitable phenomenon and one of the significant problems of deterioration of cosmetic products, like skincare products, affecting the chemical, physical, and sensorial features. Thus, it is important to study the product's behavior during its lifetime, based on scientific and reproducible methods. In this work, the skincare products of different compositions were tested, stored at 30ºC, in the absence of light, for six months. During each month, a set of samples (from A to J) were taken. It was made sensory analysis (verification of color, odor, and appearance changes) and put them in the freezer until further analysis. For each skincare product, the primary oxidation products were determined by the conjugated dienes (DC) method expressed as a percentage and by the Peroxide Value (IP) method expressed in meqO2/kg dry sample. Secondary oxidation products were also determined using the pAnidisin Value (ipA) and the 2-Thiobarbituric Acid Reactive Substances (TBARS) test, expressed as malonaldehyde concentration (mg/g dry sample). Initially, it is concluded that the choice of solvent does not influence the results obtained. In the determination of the Peroxide Value (IP) according to the iodometric method and the colorimetric method, it is observed that both present high sensitivity and a good correlation with each other, with the advantage, that the second requires fewer sample quantities, solvent and less time of analysis in the laboratory. It is concluded that the skincare products that have the greatest extent of lipid oxidation, based on the results obtained from Total Oxidation Value (TOTOX), is the Cream J. On the other hand, Cream D is the one with a smaller extent of lipid oxidation. The presence of saturated fatty acids inhibits the process of lipid oxidation and decrease the oxidation rate. Also, the presence of additives, such as tocopherol, can act as pro-oxidant or antioxidant.
Skincare products are functional products, consisting of multiple ingredients with several functions. Traditionally, one of the main ingredients are lipids that can be saturated or unsaturated. These unsaturated lipids and their interaction with the other components of the skincare products and external factors allow understanding and predicting the occurrence of oxidation. Lipid oxidation is a spontaneous and inevitable phenomenon and one of the significant problems of deterioration of cosmetic products, like skincare products, affecting the chemical, physical, and sensorial features. Thus, it is important to study the product's behavior during its lifetime, based on scientific and reproducible methods. In this work, the skincare products of different compositions were tested, stored at 30ºC, in the absence of light, for six months. During each month, a set of samples (from A to J) were taken. It was made sensory analysis (verification of color, odor, and appearance changes) and put them in the freezer until further analysis. For each skincare product, the primary oxidation products were determined by the conjugated dienes (DC) method expressed as a percentage and by the Peroxide Value (IP) method expressed in meqO2/kg dry sample. Secondary oxidation products were also determined using the pAnidisin Value (ipA) and the 2-Thiobarbituric Acid Reactive Substances (TBARS) test, expressed as malonaldehyde concentration (mg/g dry sample). Initially, it is concluded that the choice of solvent does not influence the results obtained. In the determination of the Peroxide Value (IP) according to the iodometric method and the colorimetric method, it is observed that both present high sensitivity and a good correlation with each other, with the advantage, that the second requires fewer sample quantities, solvent and less time of analysis in the laboratory. It is concluded that the skincare products that have the greatest extent of lipid oxidation, based on the results obtained from Total Oxidation Value (TOTOX), is the Cream J. On the other hand, Cream D is the one with a smaller extent of lipid oxidation. The presence of saturated fatty acids inhibits the process of lipid oxidation and decrease the oxidation rate. Also, the presence of additives, such as tocopherol, can act as pro-oxidant or antioxidant.
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Keywords
Cremes de rosto Oxidação lipídica Métodos para determinação da oxidação lipídica Skincare products Lipid oxidation Methods for determination of lipid oxidation