No abstract

The aim of this study was to evaluate lactose hydrolysis between two different initial temperatures of enzymatic and fermentation action to improve the fermentation period by checking the components formed and hydrolysis levels of lactose by HPLC. pH and titratable acidity analysis between treatments - higher initial temperature (HIT), 42 ºC, and lower initial temperature (LIT), 30 ºC - were different (P<0.05) during the fermentation process. HIT obtained lower pH and higher titratable acidity values as 4.6±0.04 and 0.73±0.01 g lactic acid.100 mL-1, respectively, against 4.82±0.01 and 0.64±0.01 g lactic acid.100 mL-1 from LIT. Lactose content was different (P<0.05) between treatments while fermenting; however, at the end of the fermentation, it reached 4.565±0.34 mg.mL-1 and 4.398±0.18 mg.mL-1 for LIT and HIT (P>0,05), respectively. Glucose and galactose remained buoyant during the fermentation period, which indicates its production and consumption at the same time by the lactic acid bacteria involved. The lactic acid concentration in LIT was higher (P<0.05) (18.64±0.62 mg.mL-1) than in HIT (17.56±0.53 mg.mL-1) although citric and acetic acids content decreased throughout the process. In conclusion, the lactase enzyme contributed to reduce the lactose content without affecting the fermentation process. In addition, both treatments obtained lower values of lactose, which is sufficient for the consumption by those who have lactose malabsorption.

The research aimed to evaluate the behavior of different concentrations of lutein added in sheep milk yogurt. The work verified the effect on acidity, pH, color, lutein degradation, and recovery during storage. Different added lutein concentration into yogurt were comparedI: 0.00 mg; 3.0 mg; 3.45 mg; and 3.9 mg (•100 mL-1). Analyzes were performed on days 1 st , 15 th , 30 th , and 45 th of refrigerated storage (5 °C). Lutein did not influence fermentation patters, but post acidification was observed, mainly in groups with the highest lutein concentrations. The amount of lutein recovered was different between groups (P < 0.05) due to treatment. Some differences (P < 0.05) in the same treatment occurred over time, tending to decrease lutein recovery. For all treatments, up to the end of storage, the final amount of lutein characterized the product as a nutritional source of this element. However, lutein recovery in G4 has reached the minimum daily intake recommended by researchers for health benefits. Recovery ranged from 81.9 ± 0.76•100-1 (w•w-1) to 76.31 ± 1.07•100-1 (w•w-1) on the storage period. L* has no difference (P > 0.05) between groups with different added lutein concentrations. On contrast, a*, b*, c*, and YO (yellowness index) were different (P < 0.05).

The purpose of this study was to evaluate the behavior of E. coli O157:H7 during lactose hydrolysis and fermentation of traditional and low lactose yogurt. It also aimed to verify E. coli O157:H7 survival after 12 h of storage at 4 °C ±1 °C. Two different types of yogurts were prepared, two with whole milk and two with pre-hydrolyzed whole milk; in both groups one yogurt was inoculated with E. coli O157:H7 and the other one was not inoculated. The survival of E. coli and pH of yogurt were determined during fermentation and after 12-h refrigeration. The results showed that E. coli O157:H7 was able to grow during the fermentation period (from 4.34 log CFU.mL -1 to 6.13 log CFU.mL -1 in traditional yogurt and 4.34 log CFU.mL -1 to 6.16 log CFU.mL -1 in low lactose yogurt). The samples with E. coli O157:H7 showed gas formation and syneresis. Thus, E. coli O157:H7 was able to survive and grow during fermentation of traditional and low lactose yogurts affecting the manufacture technology. Moreover, milk contamination by E. coli before LAB addition reduces the growth of L. bulgaricus and S. thermophilus especially when associated with reduction of lactose content Keywords: β-galactosidase; EHEC; fermented milk; lactic acid bacteria; lactose hydrolysis. ResumoObjetivou-se no presente estudo avaliar o comportamento da E. coli O157:H7 durante o processo de hidrólise da lactose e fermentação de iogurte tradicional e com teor reduzido de lactose. Além disso, objetivou-se verificar a viabilidade da E. coli O157:H7 e a viabilidade das bactérias ácido láticas após 12 h de estocagem a 4 °C ±1 °C. Dois diferentes tipos de iogurte com amostras controle e amostras inoculadas foram preparados, sendo dois com leite integral e dois com leite integral pré-hidrolisado; em ambos os grupos um foi inoculado com E. coli O157:H7 e um não foi inoculado. A 2 Cienc. anim. bras., Goiânia, v.18, 1-9, e-39554, 2017Escherichia coli O157:H7 survival in traditional and low lactose yogurt during fermentation sobrevivência da E. coli e o pH dos iogurtes foram determinados durante a fermentação e após 12h de refrigeração. A partir dos resultados observou-se que a E. coli O157:H7 foi capaz de se multiplicar ou manter-se viável durante a fermentação (4,34 UFC.mL -1 para 6,13 UFC.mL -1 no iogurte tradicional e 4,34 UFC.mL -1 para 6,16 log UFC.mL -1 em iogurte com lactose reduzida). Nas amostras inoculadas com E. coli O157:H7 houve formação de gás e sinérese. Dessa forma, concluiu-se que a E. coli O157:H7 foi capaz de sobreviver e de se multiplicar durante a fermentação afetando a tecnologia de fabricação. Além disso, a contaminação do leite antes da adição das BAL reduziu o crescimento de L. bulgaricus e S. thermophilus, especialmente quando associado à redução da lactose. Palavras-chave: β-galactosidase; bactérias ácido láticas; EHEC; hidrólise da lactose; leite fermentado.

No abstract