(160b) Influence of Whey Protein Edible Film and Refrigeration Temperature on Quality of Acerola in Natura during Postharvest Storage

Acerola (Malpighia emarginata D.C.) is a tropical fruit of great nutritional value, especially because of its high content of vitamin C. Acerola quality during postharvest depends on storage condition, being storage temperatures from 5 to 15 °C the best conditions for the conservation of acerola in natura, which also depends on the packaging employed. Storage of acerola at low temperatures can lead to cold damage, while storage at high temperatures leads to microbial growth. Beyond refrigeration, application of edible biofilm is another method to improve fruit quality. Studies suggest that films obtained from whey, apart from the antimicrobial effects, are transparent, have flexibility and the absence of odor and flavor, which favors consumer acceptability. In addition, the films can act as a semi-permeable barrier to moisture, oxygen and external damage, and can combat the symptoms of cold injuries. One of the main cold damages is changes in acerola color, which occurs due to chances in anthocyanins content. Changes in color cause a visual impact in consumers and are a predominant factor in decision making for fruit consumption. Also, the higher the anthocyanin content, the better acceptance of the product by the consumer. Besides that, microbial growth is also an important parameter in acerola quality, since it can promote changes in sensory attributes. Until the present moment, there are only few studies comparing the influence of temperature together with the application of biofilms on acerola quality. Thus, given the relevance of the factors addressed, the objective of this work is to study the influence of the application of biofilm formulated with 60% whey (no biofilm and biofilm) and storage temperature (5 and 10 °C) on the degradation of acerola during storage, during 12 days of storage. Acerola was sterilized with chlorinated water and, after the application of the biofilm, packed aseptically in plastic containers. Microbiological (mesophilic and psychotropic) growth, anthocyanin and color (L*a*b*) analyses were performed according to the AOAC norms. In this work, only the results for a*, referring to the red color coordinate, will be presented. The results were submitted to analysis of variance (ANOVA) and comparison of means by Tukey's test with significance of 5%. In the beginning of the experiment, anthocyanins content was 3,33 ± 0,14 mg/100g acerola. At the end of storage at 5 °C, samples stored without the edible film (NEF) presented a content of 2,12 ± 0,01 mg/100g, while the content in samples stored with the edible film (EF) was 1,40 ± 0,01 mg/100g. At the of the storage at 10 °C, anthocyanins content was 3,99 ± 0,08 mg/100g for NEF and 3,54 ± 0,02 mg/100g for EF. As could be observed, there was a significant decrease in the content at 5 °C, being higher in EF, while for 10 °C there was a small but significant increase in the content, being higher in NEF. Anthocyanins are very unstable pigments that can be degraded under various conditions, including temperature or during food processing and storage. Also, the higher the anthocyanin content, the better the acceptance of the product by the consumer, being important its measurement, because the yellowish colored fruits will probably be rejected by consumers. The color analysis showed a a* value of 47,04 ± 3,34 on day 0 of storage. At the end of the storage, a* value for NEF was 32,54 ± 1,56 and for EF was 34,08 ± 4,71, both at 5 °C, while at 10 °C, a* value for NEF was 46,68 ± 2,27 and for EF 43,00 ± 0,03. There was a significant decrease in the a* values at 5 °C. While at 10 °C no significant difference in the results was observed. At 10 °C, the results showed stability in color a*, maintaining the reddish color. In this work, it was observed that acerola stored at 5 °C had a more yellowish color, while acerola stored at 10 °C had a more reddish color (data not showed). Analyzing microbial growth, on day 0, the mesophilic count was 3,6x10⁵ ± 3,9x10⁴ CFU/g, and psychotropic count was 2,0x10⁵ ± 1,4x10⁵ CFU/g. At the end of storage at 5 °C, mesophilic count was 6,2x10⁶ ± 9,2x10⁵ CFU/g for NEF and 9,4x10⁵ ± 2,8x10⁴ CFU/g for EF, and at the end of the storage at 10 C, mesophilic counts were 5,9x10⁸ ± 1,2x10⁸ CFU/g for NEF and 1,1x10⁷ ± 1,6x10⁶ CFU/g for EF. For psychotropic, counts at day 12 were 2,2x10⁷ ± 9,9x10⁶ CFU/g (NEF) and 1,2x10⁸ ± 3,1x10⁷ CFU/g (EF) for storage at 5 °C and 6,9x10⁹ ± 4,2x10⁸ CFU/g (NEF) and 4,1x10⁹ ± 4,9x10⁹ CFU/g (EF) for storage at 10 °C. As could be noted, microbiological analyses showed a lower (Statistically significant) growth at 5 °C and with biofilm applied. However, at this temperature, low anthocyanin and a* color levels were also noted, showing a yellowish color caused by cold damage. In the analysis of mesophylls and psychotropics, at the end of the storage, a significant increase in counts was observed, for both temperatures. Comparing both temperatures, 5 °C reduces the microbial growth. The use of biofilm also reduced microbial growth in both storage temperatures. In accordance, studies show that dairy protein derivatives have antimicrobial effects. Concluding, storage at 5 °C reduced microbial growth, but increased changes in color. The application of edible film and acerolas storage at 10 °C reduces microbial growth, compared with acerola samples stored with no biofilm, and improves maintenance of acerola color, thus improving the quality of the product. This work presents an important step for the expansion of researches on the acerola in natura shelf life, being necessary its extension so that better conditions of temperature and concentration of biofilm are found. This study was financed in part by the Fundação de Amparo à Pesquisa e Inovação do Estado de Santa Catarina - Brasil (FAPESC).