Orientadora: Profa. Dra. Angélica Marquetotti Salcedo Vieira

Data da Defesa: 28/09/2018



Consumers today are looking for foods made from natural ingredients. This demand drives the application of new inputs and processing technologies in the industrial sector, with the partial or total replacement of synthetic additives with extracts of natural compounds. The Moringa seed is rich in protein, with a range of 33 to 42% oil composed mostly of 76% oleic acid. Studies evidenced the high quality of the enzyme present in the extract, making it promising for industrial purposes due to catalytic properties as well as applications as a natural thickening agent.
Due to the consumers' search for foods with natural ingredients and the properties of the Moringa seed, as a natural thickening agent, the objective of the present work was to elaborate Greek yoghurt by adding the ultrafiltered extract of the Moringa seed, verifying if there are changes in the physical-chemical properties of the seeds, chemical and technological properties of the yoghurts produced.
MATERIAL AND METHODS Moringa seeds were purchased at the Federal University of Sergipe - SE and stored in a freezer until the preparation of the salt extract, which was ultrafiltered at 1 bar, with a cellulose ester membrane with a filter area of 0.1 m2 and a cut - off curve of 5 kDa. While the milk was ultrafiltered at 0.5 bar, with cellulose ester membrane with a filter area of 0.1 m2 and a cut-off curve of 30 kDa in an ice bath. Greek yogurt was prepared using lactic acid culture (Lactobacillus acidophilus LA-5, Bifidobacteruim BB-12 and Streptococcus thermophilus) and commercial pasteurized milk, with 7% refined sugar added. Concentrated milk was heated to 42 °C, then 7% refined sugar (m v-1), lactic acid culture and Moringa seed extract were added at concentrations of 1, 2 and 3 mL L-1 (concentrated extract ) and 5, 10 and 15 mL L-1 (permeate extract). The products were stored in 100 ml plastic pots and incubated at 42 °C for fermentation, which was fixed for approximately 9 hours, where the final pH reached 4.9. At the end of the fermentation, the yogurts were stored at 4 °C until the analyzes were carried out. All the yoghurts were produced in triplicates, being named P5, P10 and P15 to add 5, 10 and 15 mL L-1 permeate, and C1, C2 and C3 to 1, 2 and 3 mL L-1 of concentrate. The control sample, without addition of Moringa extract, was denominated C. In addition to the analyzes of pH, acidity, moisture, proteins, total solids, ashes, and lipids, tests of sineresis, texture, oscillatory rheology and scanning electron microscopy of yoghurts were performed. All the tests were performed in triplicates and analyzed by Statistica® 8.0 software applying ANOVA, using Tukey test with 5% significance. The pH, acidity, texture, and synergistic analyzes were performed on days 7, 14, 21 and 28. Samples from the fourth week of storage were used for rheological analysis and the microstructure was evaluated during the second week of storage.
RESULTS AND DISCUSSION In the ultrafiltration assay, the membrane was able to concentrate more than 80% of the proteins present in the Moringa extract, the concentrated extract reached a concentration of 8 times superior to the initial extract in relation to the amount of protein, proving to be efficient the use of the module concentration of the Moringa extract.The yoghurt with the addition of the concentrated Moringa extracts had less influence in the fermentation, when compared to the addition of the permeated extracts, due to the composition of the extracts and the volumes used. However, the final fermentation time did not change. In this work, protein percentages range from 3.4 to 6.2%. While the lipids were from 5.91 to 6.32% and the total solids from 22.11 to 22.86%. The higher the addition of the extract (concentrate and permeate), the lower the solids content as a function of the volume added, due to the amount of water present in the sample. The addition of Moringa extracts (concentrate and permeate) did not influence ash content. Moisture was lower in the control sample with 77.14%, and higher in the P15 sample, which was 77.89%. The higher the volume of added extract (concentrate and permeate), the greater the moisture in the final product. Regarding pH, there was no significant difference at the 5% level for the addition of extracts (concentrate and permeate) in the products, but in relation to the storage time of these products, due to the stability of β-galactosidase enzyme, which remains active between 0 and 5 ºC during the storage period, allied to the metabolic activity of the starter cultures that ferment lactose in lactic acid, because, these bacteria are active in the storage temperature at 4 ºC, resulting in the decrease of pH and increase of acidity, which varied from 4.92 to 4.26 and 1.34 to 1.46%, respectively. The syneresis profile of the yogurts decreased (p <0.05) from the first week in relation to the fourth, due to the regrouping of the gel proteins, which establish greater protein-protein contact, improving gel strength during storage. All samples presented an increase in the hardness profile in relation to storage days, in agreement with the decrease in susceptibility to syneresis. Sample C2 provided higher hardness in the yogurt, while P15 resulted in the lowest hardness. These results were already expected since sample C2 presented the lowest syneresis, while P15, the highest syneresis. In relation to the rheology test, all formulations showed G 'values higher than G ", indicating that the samples had a behavior similar to a solid whose deformations have elastic or recoverable properties. Finally, the scanning electron microscopy (SEM) of the yoghurts showed that the addition of the concentrated and permeated extracts altered the microstructure of the yoghurts. In the C2 yoghurt the microstructure was more homogeneous and compact, and was the sample with lower syneresis and greater firmness among all the samples. Yogurts P5, P10 and P15 to microstructures are probably due to the composition of the extract permeated by peptides smaller than 5 kDa.
CONCLUSIONS From the obtained results, it was concluded that the yogurt C2 was the best formulation found, because it presented a decrease in the susceptibility to the syneresis with the increase of the firmness, while, P15 presented higher syneresis and less hardness. Therefore, it is advantageous to add the concentrated extract of the Moringa seed in the preparation of Greek yogurt, up to the concentration of 2 mL of concentrated extract of the Moringa seed per liter of milk.
Key words: Concentrated yoghurt. Ultrafiltration. Texture. Rheology. Microstructure.

 Artigos Publicados Vinculados a Dissertação: