Produção do quefir com polpa de graviola (Annona muricata) e avaliação das características microbiológicas, fisico-químicas e de sua aceitabilidade

Abstract

Kefir is a product of milk fermentation with kefir grains and cultures prepared from grains. In these grains (polysaccharide matrix), lactic bacteria and yeasts live in symbiosis and they perform alcoholic and lactic fermentation. Kefir is an old beverage originated from Caucasians Mountains. Many studies have investigated its nutritional and biotherapeutic benefits. Among its functional qualities it can be cited: relieve all intestinal disorders, antibacterial and antitumoral action, hypocholesterolemic action and others. Graviola is a well known and accepted fruit in the Amazon region. It has been produced almost through the year, which becomes easily available. Because of its qualities and searching utilization of amazon fruits, a kefir beverage was produced with graviola pulp. Its microbiological and physic-chemical characteristics were evaluated during the period of refrigerator, as well as its acceptability. Kefir was produced with 5% of grains as starter-cultures and the fermentation was divided in two stages: the first one at 25oC for 24 hours and the second one at 7oC for 24 hours. Two types of beverages were produced: a natural kefir (control) and a kefir with adde 15% of graviola pulp and 12% of sugar. These beverages were placed on glass jars with metal lid, previously sterilized and kept by refrigeration storage in commercial refrigerators at about 7oC temperature. The microbiological and physic-chemical analyses were carried out at 0, 7, 14, 21 and 28 days of storage. The acceptability test was made at 0 time of storage. The main groups of microorganisms presented in kefir were Lactobacillus, Lactococcus, yeast and acetic bacteria quantified in specific broth. The total number of microorganisms was similar for all groups, around 109 cfu/g. After 28 days of storage it was reduced to 107 cfu/g. It was verified that the addition of graviola pulp and sugar in natural kefir did not influence the behavior of its microbiota. Lactic bacterias were isolated from kefir grains and 9 bacteria were characterized as Lactococcus lactis subps. lactis. The pH did not vary significantly during 21 days of storage. The pH increased significantly with 28 days of storage under refrigeration. The acidity (% of acid lactic) increased gradually during the storage period. However, there was not significant interaction among the acidity values on natural kefir and kefir with graviola pulp. The sensorial analyzes of kefir with graviola pulp showed score acceptability from good to excellent.