Título da Dissertação: Obtenção de concentrado proteico do soro do leite adoçado com rebaudiosídeo A e avaliação de suas
propriedades funcionais.

Orientador: Prof. Dr. Silvio Cláudio da Costa

Data da Defesa: 19/03/2014



 INTRODUCTION: Stevia rebaudiana (Bert.) Bertoni features, especially in its leaves,  diterpene glycosides with high sweetening power, among which stands out rebaudioside  A (RebA). This glycoside have a sweetening capacity up to 450 times greater than sucrose, which arouses commercial interest for application in dietetic products.  Additionally, its antioxidant and insulinotropic properties can add functionality to foods and beverages. There is now a significant share of the world population looking for products with alternative sweeteners, especially diabetics and obese individuals.  Diabetes mellitus (DM), an endocrine disorder that affects millions of people worldwide, causes a series of metabolic complications. The control or mitigation of these complications involves complex treatments, and sources of natural antioxidants and hypoglycemic agents have been considered important pharmacological adjuvants.  Whey protein concentrates contain heterogeneous proteins with properties that together to those attributed to RebA, may represent an excellent dietary supplement for people  suffering from DM. We have developed a protein supplement obtained from whey by  membrane separation processes and sweetened with RebA. This supplement exhibited excellent functional and nutritional properties in diabetic animals.
OBJECTIVE: To develop a protein concentrate from whey using membrane separation processes. To determine the functional and nutritional properties of the protein concentrate in diabetic animals. MATERIALS AND METHODS: whey, provided by MILK FLORA (Florida/ PR),  was subjected to ultrafiltration with polyamide, diafiltration, nanofiltration and spray  drying in order to produce whey protein powder concentrates (CPS I and CPS II). Rebaudioside A (RebA) was obtained by extraction, separation and purification of the leaves of Stevia rebaudiana (Bert.) Bertoni, Alvarez M1 clonal variety, cultivated in the  Center for Natural Products (NEPRON) of the State University of Maringá. CPS I and CPS II were subjected to physicochemical and microbiological analyzes. The effects of supplementation of CPS II sweetened with RebA (100 mg / kg bw) were evaluated in male diabetic Wistar rats (streptozotocin, 40 mg/kg bw) over a period of 35 days. The  animals were divided into three experimental groups (n = 6 animals per group): 2 groups of diabetic animals, a control (DC) and other supplemented (DS), and one group of normal non-diabetic control animals (NC). Fasting glucose in fed state and body weight were measured weekly. At the end of the treatment the glicemic curve and glucose tolerance were determined. It was also measured water and food intake by using individual metabolic cages. The weight of the retroperitoneal and periepididimal, the gastrocnemius and soleus muscles and the various body organs were compared among  the groups. Other  biochemical parameters analized were plasma or serum glucose, triglycerides, total cholesterol, fructosamine and the enzymes aspartate aminotransferase (AST) and alanine aminotransferase (ALT), by means of automated analytical techniques and specific reagents. The results were expressed as mean ± standard error of the mean and subjected to analysis of variance (ANOVA) followed by Tukey's test (significance p < 0.05 %).
RESULTS AND DISCUSSION: The first concentrate CPS I obtained from whey by means of ultrafiltration with a 10KD membrane, nanofiltration and reverse osmosis  (180D), followed by spray drying presented 58% of protein and 24% of lactose. The CPS II developed from exhaustive nanofiltration of CPS I with a 500D membrane,  followed by spray drying , showed 74.3 % of protein and 17.3 % of lactose. The CPS II  sweetened with RebA (26 mg per 100g CPS II) had equivalent swetness to commercially available products. Diabetic mice treated daily with CPS II sweetened  with RebA showed improvement of body weight gain and reduction of hyperglycemia,  plasma levels of fructosamine, triglycerides and total cholesterol.  CONCLUSIONS: CPS II sweetened with RebA presented important results regarding  its functionality. Therefore, it can be used as supplement for individuals with diabetes.  The RebA provided a great sweetness to the protein concentrate, which makes it an good candidate for replacing artificial sweeteners currently used in this type of supplement. 
Key-words: Whey protein; membrane separation methods; redaudioside A; Dibetes mellitus;

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