Orientadora: Profa. Dra. Grasiele Scaramal Madrona

Data da Defesa: 22/02/2017



Jaboticaba is a fruit native to Brazil and belongs to the Myrtaceae family; this fruit is rich in bioactive compounds with important antioxidant activity for human health. Its peel represents approximately 50% of the fruit and it is mostly discarded as waste when it could have a profitable industrial use. Among the phenolic compounds found in the Jaboticaba peel, there are polyphenols and anthocyanins, fruit natural pigments. The stability of these compounds can be affected by factors such as pH, storage, temperature, enzymes, light and others, directly influencing degradation rates. Therefore the introduction of these natural compounds in other foods has been a challenge due to the low stability during storage and processing. Microencapsulation emerges as an alternative process, which aims to protect compounds against adverse environmental conditions, and the study of techniques such as lyophilization, and encapsulating agents to obtain microcapsules for application in food products is of great importance.
This study aimed to microencapsulate the aqueous extract of the Jaboticaba peel by lyophilization, using maltodextrin and xanthan gum; Characterize and evaluate the stability of the microcapsules in relation to temperature, pH and light; And also to apply the resulting powder in two types of gelatin matrices evaluating the color stability during storage.
To obtain the aqueous extract of Jaboticaba peel, a central composite design was used, by means of a response surface to estimate the effect of time (30 to 60 min) and temperature (40 to 80 °C) in the extraction of phenolic compounds. The phenolic compounds were extracted at 83 °C for 45 min, the volume ratio of 1: 2, peel: water was used. After that, the extract obtained was lyophilized (E) and two formulations were produced to obtain capsules in the proportion 1: 1 agent: extract, being: CapM (maltodextrin and extract) and CapMG (99,5% maltodextrin + 0.5% xanthan gum and extract). The solutions were dried by lyophilization (Liobras, model L108). This study was divided into two parts. First the microcapsule characterization was performed: powder yield, scanning electron microscopy (SEM) charactorization, phenolic compounds identification by HPLC and stability of powders with respect to pH (2.0, 3.5, 5.0 and 6.5). The stability of phenolic compounds, monomeric anthocyanins and color were evaluated for 7 days, and the samples were stored in a temperature controlled chamber at 25 °C. Total phenolic content was determined following Folin-Ciocalteu spectrophotometric method, monomeric anthocyanins were quantified according to the differential pH method and color was determined in a portable colorimeter (CIELab system). Solubilized gelatin powders were used according to the manufacturer's recommendations, adding 0.6% of samples E, CapM and CapMG, and the color variations (ΔΕ) were evaluated for 60 days, at storage temperature of 4 °C. In the second part of this study, the powder stability was evaluated during 36 days under different storage conditions; With and without light and at 25 or 4 °C, on days 1, 9, 18, 27 and 36, quantifying levels of phenolic compounds, monomeric anthocyanins and color. Extract E, CapM and CapMG powders (1.8% concentration) were used in uncolored and unflavored gelatin solubilized in water, according to the manufacturer's recommendations. Samples were maintained at 4 °C and color was analyzed for 60 days. Afterwards the capsule which presented the lowest color variation was used in new gelatin in order to evaluate the stability to light for 60 hours, light exposure or dark chamber at 20 °C. The results were evaluated by ANOVA and Tukey test (p <0.05) using Sisvar.
In the first part of this work, it was observed that the best condition for aqueous extraction of phenolic compounds was at 80 °C and 45 minutes. After obtaining the aqueous extract, extract E (100% pure extract), CapM (50% maltodextrin + 50% extract) and CapMG (50% maltodextrin and xanthan gum + 50% extract) were microencapsulated by lyophilization, obtaining the final product, dry powder. In the production of CapM and CapMG, 80.0% encapsulation efficiency was observed for anthocyanins and the process had an approximate yield of 67.2%. Quantification of phenolic compounds by HPLC resulted, in decreasing order, of Cyanidin-3-glucoside, Gallic and Ellagic acids, and finally quercitin. For scanning electron microscopy (SEM), lyophilized microcapsules were shown as smooth structures of variable sizes and irregular shapes similar to broken glass, as already reported by other authors. In relation to the stability (t0 and t7 days) of powders against pH (2.0, 3.5 and 6.5), based on color parameters, sample luminosity (L*) was higher at lower pH (2.0 and 3.5), indicating that the solutions were brighter, lighter colors, consequently at higher pH values (6.5), the samples tended to a darker color. This is due to the fact that anthocyanins are affected mainly by acid solutions, the color of anthocyanin tends to red, but with increasing pH the color intensity decreases, in alkaline medium, blue color is obtained. In general, the type of encapsulating agent (maltodextrin and / or xanthan gum) had no significant influence on the conditions studied. The parameter a * tending to red color remained similar in all pH solutions for the two microcapsules, except for extract (E), which had its coloration reduced with increasing pH, losing the tendency to red. Regarding the stability of monomeric anthocyanins at different pH, the microencapsulated samples did not differ significantly from each other at lower pH (2.0 and 3.5). On the seventh day of storage in pH 3.5 and 6.5 the pure extract contained no more anthocyanins, unlike microcapsules that at pH 3.5 still resulted in presence of anthocyanins. This happens because pH is one of the factors that most influence anthocyanin coloration, in acid or alkaline environment these end up presenting different structures, according to literature the best values of anthocyanins for fruit extracts were in pH 1.0, in contrast to pH 4.5, where a much lower value is obtained. The phenolic contents did not present statistical difference between the microencapsulated samples. Microcapsules were most unstable at pH 6.5. Some studies in dried Jaboticaba peel report values of phenolic compounds and anthocyanins below (23.73 mg GEA / g and 1.73 mg cyanidin-3-glucoside / g), as reported in the present study using the microencapsulated extract in different pH solutions (121.69 mg GEA / g and 5.63 mg cyanidin-3-glucoside / g). Use of the obtained powder in gelatin allowed the evaluation of color stability. The largest color difference (ΔE) was observed in extract E (> 5) and the lowest in CapM. ΔE values above 5 are known to indicate an obviously high color difference, thus indicating that the encapsulated samples showed better color stability in storage. In the second part, stability of powders to temperature and light, it was observed that extract (E) presented an anthocyanin degradation of 23.0 to 34.0%, and microcapsules presented lower degradation (5.5 to 14.5%). In relation to temperature, it was observed that the highest anthocyanin degradation was at 25 °C where the extract showed a reduction of 34.2%, CapM 10.9% and CapMG 5.7%, whereas in 4 °C the lowest percentage of degradation was observed varying from 0 to
3.5%. For phenolic compounds the highest degradation was observed in extract E in the presence of light at 25 °C, and the lowest degradation was in the absence of light and 4 °C. With regard to powder color the highest variation was in extract (E) and lowest in CapMG, light presence conditions and different temperatures (4 and 25 °C). In the use of colorless gelatin powders, it was observed for 60 days (4 °C) that the greatest color variation was in extract (E) and the lowest variation in CapM. Applying CapM in colorless gelatin in order to observe color stability for 60 hours in presence / absence of light at 20 °C it was observed that the highest value of ΔE was for the samples subjected to light.
Microencapsulated aqueous extract of Jaboticaba peel had high levels of Cyanidin-3-glucoside, Gallic and Ellagic acid present in the three different samples analyzed (E, CapM and CapMG), which showed peculiar morphological characteristics due to lyophilization. In relation to the stability of powders in different pH solutions, it can be concluded that the lower buffers (2 and 3.5) provide a greater capsule stability because higher pH values tend to degrade anthocyanins and phenolic compounds, affecting also the coloration of the samples. Absence of light and lower temperatures (4 ºC) provided the best results for 36 days. In relation to content of anthocyanins and phenolic compounds the microcapsules provided lower compound degradation during storage. Regarding the use of capsules in the two types of gelatin, it was observed for 60 days that the samples with addition of CapM showed less color variations. In relation to the incidence of light it was observed that there was an influence in the color variation of the gelatin with CapM, being the highest observed value of ΔΕ 3.5. Finally, we can conclude that microencapsulation by lyophilization of aqueous extract of Jaboticaba peel with different encapsulating agents can be suggested as an alternative method for stabilizing bioactive compounds and color.
Key words: Jaboticaba, phenolic compounds, lyophilization and microencapsulation.


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