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Standardization of a Method to Determine the Emulsifying Capacity of Proteins
des A.C. ils ont muri normalement, sans qu'on puisse detecter de differences significatives de taux de murissement entre les traitements. 82. EFFET DE DlFFERENTES CONCENTRATIONS D'02 ET DE C02 SUR LES MITOCHONDRIES DU CHOU-FLEUR. L. Ramo-Parada, C. Willemot, L.P. Vezina et F. Castaigne, Departement de sciences et technologie des aliments, Universite Laval, Quebec, P.Q. GIK 7P4; et Centre de recherche alimentaires de St-Hyacinthe, Agriculture Canada, St- Hyacinthe, P.Q. 12S 8E3. L 'entreposage du chou-fIeur (Brassica oleracea L.) en atmospheres controlees (A.C.). entrai'ne une alteration de la respiration, principalement une accumulation de I'acide succinique. L'objectif de ce projet a ete d'etablir l'effet in vitro et in vivo de ces A.C. sur.les mitochondries du chou-f1eur. Les effets de ces atmospheres (070 d'02 et de C02: 21-0; 3-0; 3-15; 21-15) sur l'activite mitochondriale ont ete evalues par la mesure du contr6le respiratoire, le rapport ADP/a, le dosage de la succinate deshydrogenase et de la cytochrome c oxydase, ainsi que I'observation de la structure des mitochondries par microscopie electronique.
83. SUGAR CONTENT OF PARSNIP ROOT TISSUES DURING2 LOW TEMPERATURE STORAGE. R. Y. Yada* I, V.I. Shatluck a~d Y. Kakuda', 'Department of Food Science; and 2Department of Horticultural Science, University of Guelph, Guelph, ant. NI G 2WI. Changes in the sugar content in the cortex (phloem) and cone (xylem) tissues of two parsnip (Pastinaca sativa) cultivars during low temperature storage (O°C and 95070 humidity) was investigated. Five major sugars were identified in both root tissues and included sucrose, fructose, glucose, maltose and an unidentified oligosaccharide. The sucrose concentration increased over three fold at a steady and equivalent rate in both the cortex and core tissues. Glucose, fructose, maltose and the unidentified oligosaccharide were also observed to accumulate in root tissues during the month long study. Cultivar differences for sugar levels in root tissues were noted. 84. THE IDENTIFICATION OF PYRAZINE COMPOUNDS IN MAPLE SYRUP. I. Alii, J. Bourque and R. Metussin*, Department of Food Science and Agriculture Chemistry, Macdonald College of McGiII University, Ste. Anne de Bellevue, P.Q. H9X ICO. Commercial samples of maple syrup (dark, amber) were extracted with diethyl ether and the ether phase was separated and discarded. The aqueous phase was adjusted to pH 8.5 then extracted with dichloromethane. Capillary gas chromatographic analysis of the concentrated dichloromethane extract suggested the presence of 2-methylpyrazine, 2,3-dimethylpyrazine, 2,6-dimethylpyrazine aoo trimethylpyrazine in the amber maple syrup and pyrazine, 2-methylpyrazine, 2,6-dimethylpyrazine and ethylpyrazine in the dark maple syrup. Mass spectrometric analysis confirmed the presence of these pyrazine compounds. In all likelihood, the pyrazines are formed by reactions of amino acids and sugars during heating of maple sap for processing into maple syrup. 85. POSSIBLE INFLUENCE OF STARCH GRANULE COMPOSI· TION ON LOW TEMPERATURE SWEETENING. V. Barichel· 10*, D.W. Stanley, R.Y. Yada and R.H. Coffin, Department of Food Science, University of Guelph, Guelph, ant. NIG 2WI. Differential scanning calorimetry (DSC), alpha -amylolysis, scanning electron (SEM) and light microscopy (LM) were used to investigate differences in starch granule properties between mature potato tubers of a potato cutivar susceptible to low-temperature sweetening (Norchip) and one resistant to low-temperture sweetening (ND 860-2). Tubers were stored 4 weeks at either 4 or 12C (90-95070 RH). Over the entire storage period, starch isolated from ND 860-2 displayed significantly (p
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No. 4. 1989
alpha-amylase indicated more ND 860-2 starch granules were intact compared to Norchip. These data suggest that starch granule composition may be a factor differentiating low-temperature sweetening sensitive from resistant potato cultivars. 86. ISOLATION OF CYSTATlN FROM EGG WHITE. T.D. Durance*, Department of Food Science, University of British Columbia, Vancouver, B.C. V6T IW5. Cystatin (also known as ficin inhibitor), a protein found in low concentrations in many animal tissues, is a specific inhibitor of cysteine proteinases. Affinity chromatography was the most appropriate purification procedure for this protein because of its very low concentration in egg white (Le. 40 mg/L). Ficin was inactivated with L-trans-epoxysuccinyl-Ieucylamido (4-guanidino) butane (E-64) or sodium tetrathionate and immobilized on activated agarose (Affigel-IO). Papain was also inactivated with iodoacetic acid and immobilized. Ovomucin was precipitated from egg white to reduce viscosity and the supernatant was applied to the affinity columns. Cystatin activity was monitored as inhibition of papain under standard conditions. SDS-PAGE indicated high purity in the eluted cystatin fractions. 87. PHYTATE DETERMINATION IN PROTEINS USING POLYACRYLAMIDE·DlSC GEL ELECTROPHORESIS. A.B. Di Lollo*, I. Alii and S. Kermasha, Department of Food Science and Agricultural Chemistry, Macdonald College of McGiII UniversitY,Ste. Anne de Bellevue, P.Q. H9X ICO. Protein-phytate interaction is common in cereal grains and oilseeds. The identification of complexes on polyacrylamide gels will help to provide an understanding of the nature of these interactions. A technique for identification of protein-phytate complexes on polyacrylamide gels, precipitates the phytate as a white band of ferric-phytate. A colorimetric reaction believed to be specific for iron was investigated to improve the visualization of the ferric phytate on the gels. The results indicate that white bands which are formed when protein-phytate complexes on polyacrylamide gels treated with iron solution, could be the result of protein-iron interaction in addition to phytate-iron interaction. This was confirmed by the use of proteins which contained no phytate. The effect of phytate addition to proteins was also studied. Electrophoretic analysis followed by staining of the gels for iron confirmed the complexation of proteins with iron during the phytate visualization procedure. 88. STANDARDIZATION OF A METHOD TO DETERMINE THE EMULSIFYING CAPACITY OF PROTEINS. J.C. Vuillemard*, S. Gauthier, P. Paquin and J.P. Richard, Groupe STELA, Departement de sciences et technologie des aliments, Universite Laval, Quebec, P.Q. GIK 7P4. The method of emulsion preparation influences the determination of emulsion capacity (E.C.) of food proteins. Hence, there is a need for standard method for quantifying E.C. The equipment, speed of stirring, rate of oil addition and protein concentration are the most important parameters in the determination of E.C. Protein concentration should be previously determined. The other parameters should be controlled in order to obtain an emulsion with fat globules of mean diameter 2.0 /Lm. According to our results, the E.C. should be defined as the amount of oil emulsified minus a blank divided by the amount of protein. 89. APPLICATION OF RESPONSE SURFACE METHODOLOGY IN PROTEIN EXTRACTION STUDIES FROM BREWER'S SPENT GRAIN. R. Diptee, J.P. Smith and I. Alii, Department of Food Science and Agricultural Chemistry; and S. Khanizadeh, Department of Plant Science, Macdonald College of McGilI University, Ste. Anne de Bellevue, P.Q. H9X ICO. Effects of temperature of extraction, time of extraction, concentration of sodium dodecly sulphate and Na2HP04 in the extractant solution, particle size of grain and BSG: extractant ratio on the yield of protein solubilized from dried brewer's spent grain (DBSG) and pressed brewer's spent grain (PBSG) were studied simultaneously using a process optimization technique termed Response Surface Methodology (RSM). The initial fractional factorial screening design indicated that time, temperature and particle size of grain were significant variables with concentration of
Abstract / 413
83. SUGAR CONTENT OF PARSNIP ROOT TISSUES DURING2 LOW TEMPERATURE STORAGE. R. Y. Yada* I, V.I. Shatluck a~d Y. Kakuda', 'Department of Food Science; and 2Department of Horticultural Science, University of Guelph, Guelph, ant. NI G 2WI. Changes in the sugar content in the cortex (phloem) and cone (xylem) tissues of two parsnip (Pastinaca sativa) cultivars during low temperature storage (O°C and 95070 humidity) was investigated. Five major sugars were identified in both root tissues and included sucrose, fructose, glucose, maltose and an unidentified oligosaccharide. The sucrose concentration increased over three fold at a steady and equivalent rate in both the cortex and core tissues. Glucose, fructose, maltose and the unidentified oligosaccharide were also observed to accumulate in root tissues during the month long study. Cultivar differences for sugar levels in root tissues were noted. 84. THE IDENTIFICATION OF PYRAZINE COMPOUNDS IN MAPLE SYRUP. I. Alii, J. Bourque and R. Metussin*, Department of Food Science and Agriculture Chemistry, Macdonald College of McGiII University, Ste. Anne de Bellevue, P.Q. H9X ICO. Commercial samples of maple syrup (dark, amber) were extracted with diethyl ether and the ether phase was separated and discarded. The aqueous phase was adjusted to pH 8.5 then extracted with dichloromethane. Capillary gas chromatographic analysis of the concentrated dichloromethane extract suggested the presence of 2-methylpyrazine, 2,3-dimethylpyrazine, 2,6-dimethylpyrazine aoo trimethylpyrazine in the amber maple syrup and pyrazine, 2-methylpyrazine, 2,6-dimethylpyrazine and ethylpyrazine in the dark maple syrup. Mass spectrometric analysis confirmed the presence of these pyrazine compounds. In all likelihood, the pyrazines are formed by reactions of amino acids and sugars during heating of maple sap for processing into maple syrup. 85. POSSIBLE INFLUENCE OF STARCH GRANULE COMPOSI· TION ON LOW TEMPERATURE SWEETENING. V. Barichel· 10*, D.W. Stanley, R.Y. Yada and R.H. Coffin, Department of Food Science, University of Guelph, Guelph, ant. NIG 2WI. Differential scanning calorimetry (DSC), alpha -amylolysis, scanning electron (SEM) and light microscopy (LM) were used to investigate differences in starch granule properties between mature potato tubers of a potato cutivar susceptible to low-temperature sweetening (Norchip) and one resistant to low-temperture sweetening (ND 860-2). Tubers were stored 4 weeks at either 4 or 12C (90-95070 RH). Over the entire storage period, starch isolated from ND 860-2 displayed significantly (p
22.
No. 4. 1989
alpha-amylase indicated more ND 860-2 starch granules were intact compared to Norchip. These data suggest that starch granule composition may be a factor differentiating low-temperature sweetening sensitive from resistant potato cultivars. 86. ISOLATION OF CYSTATlN FROM EGG WHITE. T.D. Durance*, Department of Food Science, University of British Columbia, Vancouver, B.C. V6T IW5. Cystatin (also known as ficin inhibitor), a protein found in low concentrations in many animal tissues, is a specific inhibitor of cysteine proteinases. Affinity chromatography was the most appropriate purification procedure for this protein because of its very low concentration in egg white (Le. 40 mg/L). Ficin was inactivated with L-trans-epoxysuccinyl-Ieucylamido (4-guanidino) butane (E-64) or sodium tetrathionate and immobilized on activated agarose (Affigel-IO). Papain was also inactivated with iodoacetic acid and immobilized. Ovomucin was precipitated from egg white to reduce viscosity and the supernatant was applied to the affinity columns. Cystatin activity was monitored as inhibition of papain under standard conditions. SDS-PAGE indicated high purity in the eluted cystatin fractions. 87. PHYTATE DETERMINATION IN PROTEINS USING POLYACRYLAMIDE·DlSC GEL ELECTROPHORESIS. A.B. Di Lollo*, I. Alii and S. Kermasha, Department of Food Science and Agricultural Chemistry, Macdonald College of McGiII UniversitY,Ste. Anne de Bellevue, P.Q. H9X ICO. Protein-phytate interaction is common in cereal grains and oilseeds. The identification of complexes on polyacrylamide gels will help to provide an understanding of the nature of these interactions. A technique for identification of protein-phytate complexes on polyacrylamide gels, precipitates the phytate as a white band of ferric-phytate. A colorimetric reaction believed to be specific for iron was investigated to improve the visualization of the ferric phytate on the gels. The results indicate that white bands which are formed when protein-phytate complexes on polyacrylamide gels treated with iron solution, could be the result of protein-iron interaction in addition to phytate-iron interaction. This was confirmed by the use of proteins which contained no phytate. The effect of phytate addition to proteins was also studied. Electrophoretic analysis followed by staining of the gels for iron confirmed the complexation of proteins with iron during the phytate visualization procedure. 88. STANDARDIZATION OF A METHOD TO DETERMINE THE EMULSIFYING CAPACITY OF PROTEINS. J.C. Vuillemard*, S. Gauthier, P. Paquin and J.P. Richard, Groupe STELA, Departement de sciences et technologie des aliments, Universite Laval, Quebec, P.Q. GIK 7P4. The method of emulsion preparation influences the determination of emulsion capacity (E.C.) of food proteins. Hence, there is a need for standard method for quantifying E.C. The equipment, speed of stirring, rate of oil addition and protein concentration are the most important parameters in the determination of E.C. Protein concentration should be previously determined. The other parameters should be controlled in order to obtain an emulsion with fat globules of mean diameter 2.0 /Lm. According to our results, the E.C. should be defined as the amount of oil emulsified minus a blank divided by the amount of protein. 89. APPLICATION OF RESPONSE SURFACE METHODOLOGY IN PROTEIN EXTRACTION STUDIES FROM BREWER'S SPENT GRAIN. R. Diptee, J.P. Smith and I. Alii, Department of Food Science and Agricultural Chemistry; and S. Khanizadeh, Department of Plant Science, Macdonald College of McGilI University, Ste. Anne de Bellevue, P.Q. H9X ICO. Effects of temperature of extraction, time of extraction, concentration of sodium dodecly sulphate and Na2HP04 in the extractant solution, particle size of grain and BSG: extractant ratio on the yield of protein solubilized from dried brewer's spent grain (DBSG) and pressed brewer's spent grain (PBSG) were studied simultaneously using a process optimization technique termed Response Surface Methodology (RSM). The initial fractional factorial screening design indicated that time, temperature and particle size of grain were significant variables with concentration of
Abstract / 413