José Virgílio Coelho

PROPRIEDADES EMULSIONANTES E SOLUBILIDADE DA CASEÍNA BOVINA: 2. EFEITO DA ADIÇÃO DE NaCl

The effect of the NaCl addition on the emulsifying properties of casein and tryptic casein hydrolysates was studied in two pH values (4,0 e 5,0). A 0.02 M concentration of salt was added to the buffer solutions used for preparing the samples. The protein solubility, the emulsifying capacity (EC), the emulsifying activity index (EAI) and the emulsion stability (ES) were determined. The mean radius (R) of fat droplets was also calculated. The results showed that the addition of NaCl increased the solubility and the EC of casein and casein hydrolysates, in both pH values. However, this salt addition reduced the EAI of casein and increased that of the hydrolysates.The opposite was observed relating to the R of fat droplets. Regarding the ES, that of casein presented little increase in pH 5.0, and the same result was obtained for only some hydrolysates in pH 5.0 or 4.0.

PROPRIEDADES EMULSIFICANTES E SOLUBILIDADE DA CASEÍNA BOVINA E DE SEUS HIDROLISADOS TRÍPTICOS: 1. EFEITO DO PH E DO TEMPO DE HIDRÓLISE

The effects of pH and hydrolysis time on the solubility and emulsifying properties were studied, in view of the industrial application of casein and its tryptic hydrolyzates. It has been tested the pH values of 3,0; 4,0; 5,0; 6,0; 7,0 and 8,0 and the reaction times: 5, 10, 15, 30 and 60 min. It has been evaluated the solubility, the emulsifying capacity, the emulsifying activity index and the emulsion stability. The results show that the best values for the functional properties of native casein were achieved at pH above 5,0. The tryptic hydrolysis of casein favored the solubility and emulsifying capacity but reduced the emulsion stability, at all pH and hydrolysis times, except in pH 5,0 with 5min of reaction. Otherwise, this enzymatic treatment improved the emulsifying activity index of casein only between pH 3,0- 5,0, after 10 min of reaction.

Ação da pancreatina na obtenção de hidrolisados protéicos de soro de leite com elevado teor de oligopeptídeos

Several enzymatic hydrolysates of whey were prepared with the objective of increasing the oligopeptide content and reducing the cost of large scale production. Pancreatin was used and some hydrolytic parameters such as reaction time (5, 10 and 15h), enzyme:substrate ratio (E:S) (1:100, 2:100 and 4:100) and substrate concentration (10 and 15%) were tested. The hydrolysates were fractionated by size-exclusion-HPLC and the rapid corrected fraction area method was used for quantifying the chromatographic fractions. The beneficial effect on the peptide profile was observed in several cases, and it was mainly associated with higher oligopeptide (49%) and lower amino acid (22%) contents, which were obtained for a substrate concentration of 10%, E:S ratio of 4:100 and reaction time of 10h.

Extração química e enzimática das proteínas do fubá de milho

Diferentes metodos quimicos e um enzimatico foram testados para extracao das proteinas do fuba de milho. A avaliacao do rendimento da extracao proteica foi feita pela determinacao do teor de proteina e de solidos totais dos residuos obtidos. Para a extracao quimica das proteinas, uma solucao alcalina, isoladamente ou em associacao com etanol, foi empregada como solvente. O metodo alcalino-alcoolico sequencial foi o mais eficiente, dentre os metodos quimicos testados, tendo alcancado 88,2% de rendimento. Por outro lado, o metodo alcalino (75,5% de rendimento) apresenta a vantagem de nao empregar etanol, reduzindo os custos do processo, pois se evita a etapa de remocao desse solvente. Para a extracao enzimatica, foi utilizada uma protease de Bacillus liccheniformis. As variaveis, tempo e temperatura, empregadas no metodo enzimatico influenciaram no rendimento da extracao proteica do fuba de milho. Os melhores resultados foram obtidos em 5, 15 e 24 h a 55 °C, que nao apresentaram diferenca significativa, sendo que a condicao mais vantajosa do ponto de vista economico foi a de 5 h a 55 °C com um rendimento de 83,8%.

Screening filamentous tropical fungi for their nutritional potential as sources of crude proteins, lipids and minerals.

The use of fungal and yeast biomass in foodstuff, either as supplements or as major ingredients in formulations is an area of growing interest for the modern food industry. The aim of this study was to evaluate the nutritional potential of biomasses obtained from filamentous fungi Penicillium sclerotiorum, Penicillium janthinellum, Rhizopus stolonifer and Syncephalastrum racemosum. Biomasses presented 26-37% of total proteins, 1.7-3.5% of lipids and 4.6-9.1% of ashes. The humidity level reached 75-83%. Ashes were screened for minerals contents with a special outcome for S. racemosum biomass that presented 3438 mg/100 g (dw) of magnesium. Fatty acids present in the biomasses were screened and the palmitic (C16:0), estearic (C18:0), elaidic (18:1n9-t), oleic (18:1n9-c), linolelaidic (C18:2n6-t), linoleic (C18:2n6-c) and γ-linolenic (C18:3n6) acids were found to be the most abundant, from a total of 88-90% of identified fatty acids. Overall data indicate that the filamentous fungi studied have good nutritional properties, possessing a combination of good level of proteins, low level of fat, and presence of essential fatty acids, including omega-3 derivatives, along with the presence of Ca, Mg, Zn and Fe.