Influência de coating à base de amido e Manosileritritol Lipídios (MEL) na vida útil de goiaba cv. “Paluma”

Abstract

A goiaba (Psidium guajava L) é um fruto tropical, atrativo aos consumidores por suas características sensoriais e nutricionais. A fim de estender a vida útil de frutos, a aplicação de coating vem sendo amplamente discutida, principalmente, para frutos perecíveis, como as goiabas. O presente trabalho tem por objetivo estudar a influência de coating à base de amido com diferentes concentrações de manosileritritol lipídios (MEL) nas características físico-químicas de goiaba cv. “Paluma”. As goiabas foram adquiridas em estágio de pré-maturação, avaliadas visualmente, e então revestidas com coating de amido e amido e MEL nas concentrações de 0,05, 0,15 e 0,30 g de MEL/ g amido seco. O coating foi preparado fazendo uma dispersão de amido (2%) e em seguida o MEL foi adicionado. As goiabas com e sem coating foram armazenadas a 25 ± 3 °C e 85 ± 10% de UR. A superfície das goiabas foi avaliada por ângulo de contato com a água e com as suspensões de coating por microscopia eletrônica de varredura (MEV). Análises de cor, testes de perfuração, pH, sólidos solúveis totais (SST) e perda de massa (%) foram avaliados durante o armazenamento. A taxa de respiração dos frutos foi acompanhada pela composição gasosa (%O2 e %CO2) utilizando-se recipientes de vidro. Os resultados mostraram que o ângulo de contato entre a superfície da goiaba e as suspensões contendo MEL diminui, o que representa uma maior molhabilidade da superfície quando o biossurfactante está presente na formulação. O uso de coatings mostrou-se eficiente quanto ao retardamento do escurecimento da casca da goiaba e da degradação da cor verde apresentando diferença significativa (p<0,05) quando comparado à amostra controle. Esse comportamento foi acompanhado para a cor interna das goiabas, sendo que o parâmetro a* da escala CieLab para as amostras controle apresentou-se superior no quarto e no sétimo dia de armazenamento quando comparado às amostras revestidas. Os frutos revestidos com 0,30 g de MEL/g de amido seco, a partir do quarto dia de armazenamento, apresentaram diferença significativa quanto à força de penetração, ou seja, maior resistência da casca ao rompimento. Da mesma forma, a dureza e a força média aumentaram com o aumento da concentração do biossurfactante no coating. Todas as amostras apresentaram perda de massa crescente e não diferiram estatisticamente (p>0,05). A taxa respiratória das amostras sem coating foi maior do que das amostras com coating. No 11° dia, o valor médio de produção de CO2 para as amostras sem coating foi de 52,8%, enquanto para as amostras com 0,30 g de MEL/g de amido seco foi de 27,57%. De maneira geral, os coatings de amido com MEL afetaram de forma positiva os parâmetros de qualidade das goiabas acarretando no aumento da vida útil desses frutos.

Guava (Psidium guajava L) is a tropical fruit, attractive to consumers for its sensory and nutritional characteristics. In order to maintain fruit quality longer, the application of coating has been widely discussed, especially for very perishable fruits such as guavas. The present work aimed to study the influence of starch-based coating with mannosylerythritol lipids (MEL) on the physicochemical characteristics of guava cv. Paluma. The guavas used in the study were purchased at the CEASA/SC unit located in São José, SC. Yoki Alimentos S / A brand cassava starch was purchased from local merchants and MEL biosurfactant was imported from Toyobo Co., Ltd., Osaka. Coating without addition of MEL was named Starch, whereas coatings containing biosurfactant were named MEL 0.05, MEL 0.15 and MEL 0.30, indicating the ratio of MEL mass to starch mass. (g MEL / g starch on wet basis). The coating was prepared by making a starch dispersion (2%) and then the MEL was added. After the coated guavas, all were stored at 25 ± 3 ° C and 85 ± 10% RH. Color analysis, mechanical tests, pH, total soluble solids (TSS) and mass loss (%) were evaluated on the 1st, 4th, 7th, 11th and 13th day of storage. Contact angle analyzes and scanning electron microscopy (SEM) were also performed. Measurements for gaseous composition evaluation (% O2 and% CO2) in the packages in which samples of each treatment were packed were made on the 1st, 3rd, 5th, 7th, 9th and 11th days of storage. Regarding surface properties, it was concluded that there was a decrease in contact angle and improved wettability with the incorporation of MEL to starch coating. The use of coatings proved to be efficient in delaying guava peel darkening and green color degradation, presenting significant difference (p <0.05) in the control sample. For pulp, a* values were observed for control samples significantly higher than the others on the fourth and seventh day of storage. Penetration tests showed that fruits with MEL 0.30, from the fourth day of storage, showed significant difference in penetration force, ie, greater peel resistance to breakage. For firmness, samples with coatings MEL 0.30 and MEL 0.15. Similarly, hardness and average strength increased with increasing biosurfactant concentration in the coating. Guava texture related parameters showed high deviations in the assays, which is possibly attributed to the great heterogeneity between the samples. No significant differences in pH and TSS were identified between the samples. All samples showed increasing mass loss and did not differ statistically. There was a much higher concentration of carbon dioxide in the control guava packaging during the analysis period, and on the last day the average value for these samples was 52.8% compared to 27.57% of the MEL 0,30. In general, the starch coatings with MEL positively affected the quality parameters of guavas, leading to increased shelf life of these fruits.