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UHT-processing of Foods: State of the Art and Future Applications
ABSTRACTS of Papers presented at the 28th Annual CIFST Conference June 23-26, 1985 THE ROLE OF CALCIUM IN CASEIN MICELLE STRUCTURE. Michel Britten*, Paul Paquin, Marcel Boulet. Departement de sciences et technologie des aliments et Centre de recherche en nutrition, Universite Laval, Quebec, Canada GIK 7P4. The effect of chelation of calcium on structural properties of casein micelles has been investigated. Dialysis of primary casein micelles against EDTA solution led to the separation of micelles in two proteic fractions. The surface properties of these fractions were determined using the film monolayer technique. Our results showed that the first fraction had a specific area of 130 m 2g- l , corresponding to the sub-units. The second fraction, with a specific area of 1300 m2g- 1 represents dissociated caseins, which have been released by calcium chelation. The gel electrophoresis patterns revealed an assymetric distribution of a-and ~-caseins between the two fractions. The dissociated caseins fraction showed a higher content in a-casein, while the x-casein was more concentrated in the sub-units fraction. These results are discussed in relation with the structural model of casein micelle. INTERPRETATION OF THE ELECTROPHORETIC MOBILITY OF CASEIN MICELLES. Pouliot*, Yves; Paquin, Paul and Boulet, MarceI. Departement de sciences et technologie des aliments et Centre de recherche en nutrition. Universite Laval, Quebec, Canada GIK 7P4. The casein micelles represent the main proteic portion of milk. They are found as negatively charged colloidal particles and they show electrokinetic properties. We have combined the use of a preparative gel filtration method (Boulet et al., 1970) and of a free boundary electrophoresis method (Darling and Dickson, 1979) to determine the zeta potential of these casein micelles in a low ionic environment. We have induced various compositional changes (modifying charge density or ionic double layer) on the micelles which affected their zeta potential value. According to the DLVO theory (Verwey and Oberveek, 1948), the zeta potential of these particles has been interpretated from the contribution of two parameters: the fixed charges of the spheres and the counter-ions effect of the ionic double layer. The results obtained from this study show the importance of the ionic equilibrium between serum and colloidal phase during industrial processing involving heat treatments. UP-DATE ON THE INTERNATIONAL DAIRY FEDERATION. D.B. Emmons, Food Research Institute, Research Branch, Agriculture Canada, Ottawa, Ont., KIA OC6. The Canadian National Committee of I.D.F. (FIL-IDF Canada) continues to be active. Information will be given on recent and future seminars, symposia and workshops. IDF documents and IDF standards on a wide range of topics are available individually, or less expensively by annual subscription, through the Secretariat of IDF Canada (Mrs. Lise Rodgers, c/o Animal Production Division, Agriculture Canada, Ottawa, KIA OC5). Of particular interest, FILIDF Canada will host, the XXIII International Dairy Congress in 1990, the next b~ing in The Hague in 1986. UHT-PROCESSING OF FOODS: STATE OF THE ART AND FUTURE APPLICATIONS. H. Reuter*, Institute of Process Engineering, Federal Dairy Research Centre, Kiel University, Kiel, West Germany. The general principle of thermal treatment of foods is to employ the highest possible temperature treatment for a short time. Developments in sterilization techniques reflect this general principle and aim to improve the heat transfer into the product and our of the product to achieve heating and cooling of the product as fast as possible. Sterilization processes using the so-called 'Ultra-hightemperatures', UHT-process, are good examples of this trend. An
Can. Inst. Food Sci. Technol. J. Vo!. 18, No. 3, 1985
integral part of this process is the aseptic packaging of heat treated products. Application of UHT-processing technology to: homogeneous liquid products, liquid products with small particles and particulate foods with or without a liquid phase will be discussed with respect to equipment and thermal efficiency optimization. RAPID DIFFERENTIATION OF DAIRY LACTIC BACTERIA BY ENZYME SYSTEMS. B.H. Lee*, S. Hache and R.E. Simard, St-Hyacinthe Food Research Centre, Agriculture Canada and Dept de Science & Technologie des Aliments, Universite Laval, Ste-Foy, P.Q. GIK 7P4. The APIZYM (19 enzymes) tests within 4 hrs, along with arginine dihydrolase, citratase and lactate dehydrogenases have been applied to streptococci (18), lactobacilli (12), leuconostoc (5) and commercial lactic starters (6). Streptococcus spp. in general showed high levels of acid and alkaline phosphotases but produced no betagalactosidase, except for Str. thermophilus. Lactobacillus spp. showed strong leucine- and valine-aminopeptidases and betagalactosidase but contained no arginine dihydrolase and citratase. Str. jaecalis was readily distinguishable from Str. lactis on the basis of butyrate esterase which was not detected in the latter. Heterofermentative lactobacilli differed from homofermentative lactobacilli in possessing arginine dihydrolase and citratase but in failing to produce leucine-aminopeptidase and phosphoamidase. MICROBIAL QUALITY OF RAW AND ROASTED KEBAB. Khalaf S. AI-Delaimy* and S.H. Mohamed, Department of Biology, College of Science, University of Baghdad, Baghdad, IRAQ. The aim of this study is to establish microbiological data of raw and roasted kebab. Forty samples of each of raw and roasted kebab collected from 4 restaurants were used in this study. In raw kebab, the average counts of APC, coliform, S. aureus and molds & yeasts were 3.8 x 107/g, 5.9 X 105/g, 2.5 X 105 /g, and 2.5 x 104/g, respectively. After roasting, the counts were 2 x 104 /g, for APC, I 17/g for coliform, 62/g for S. aureus and no growth for molds & yeasts. Salmonella was found in 20 of the raw samples. 950/0 of S. aureus isolates were coagulase positive. INHIBITION OF FOOD-BORNE PATHOGENIC BACTERIA BY GARLIC EXTRACTS. Sajida H. Ali* and KhalafS. AI-Delaimy*, Department of Food Science & Department of Biology, University of Baghdad, Baghdad, IRAQ. Water and ethanol extracts of garlic (Allium sativum L) were prepared and evaluated for their ability to inhibit various food-borne pathogenic bacteria. A concentration of 200-300 "I of water or ethanol extracts of garlic effectively inhibited Bacillus cereus, Staphylococcus aureus and Yersinia enterocolytica. Salmonella typhimurium was the least sensitive tested organism which needed > 400 "I of garlic extract for its inhibition. GROWTH AND ACID PRODUCTION BY LACTOBACILLUS SP IN THE PRESENCE OF EUGENOL. A.A. Adejumo* and G. Blank, Department of Food Science, University of Manitoba, Winnipeg, Manitoba R3T 2N2. Lactobacillus organisms isolated from fermented meat sausage were grown in an eugenol-based medium. Increasing concentrations of eugenol (.01 to .12% v/v) decreased both growth and titratable acidity, indicating lethality. Filtrates obtained from washed cells of these organisms grown in the presence of eugenol showed absorbancy at 260 and 280 nm, indicating leakage of intracellular components. Proteins and ATP were also shown to be some of the leakage products Cellular fatty acid analysis indicated a decrease in saturated fatty acids, and an increase in unsaturated and branched
Institute Affairs / xxxiii
Can. Inst. Food Sci. Technol. J. Vo!. 18, No. 3, 1985
integral part of this process is the aseptic packaging of heat treated products. Application of UHT-processing technology to: homogeneous liquid products, liquid products with small particles and particulate foods with or without a liquid phase will be discussed with respect to equipment and thermal efficiency optimization. RAPID DIFFERENTIATION OF DAIRY LACTIC BACTERIA BY ENZYME SYSTEMS. B.H. Lee*, S. Hache and R.E. Simard, St-Hyacinthe Food Research Centre, Agriculture Canada and Dept de Science & Technologie des Aliments, Universite Laval, Ste-Foy, P.Q. GIK 7P4. The APIZYM (19 enzymes) tests within 4 hrs, along with arginine dihydrolase, citratase and lactate dehydrogenases have been applied to streptococci (18), lactobacilli (12), leuconostoc (5) and commercial lactic starters (6). Streptococcus spp. in general showed high levels of acid and alkaline phosphotases but produced no betagalactosidase, except for Str. thermophilus. Lactobacillus spp. showed strong leucine- and valine-aminopeptidases and betagalactosidase but contained no arginine dihydrolase and citratase. Str. jaecalis was readily distinguishable from Str. lactis on the basis of butyrate esterase which was not detected in the latter. Heterofermentative lactobacilli differed from homofermentative lactobacilli in possessing arginine dihydrolase and citratase but in failing to produce leucine-aminopeptidase and phosphoamidase. MICROBIAL QUALITY OF RAW AND ROASTED KEBAB. Khalaf S. AI-Delaimy* and S.H. Mohamed, Department of Biology, College of Science, University of Baghdad, Baghdad, IRAQ. The aim of this study is to establish microbiological data of raw and roasted kebab. Forty samples of each of raw and roasted kebab collected from 4 restaurants were used in this study. In raw kebab, the average counts of APC, coliform, S. aureus and molds & yeasts were 3.8 x 107/g, 5.9 X 105/g, 2.5 X 105 /g, and 2.5 x 104/g, respectively. After roasting, the counts were 2 x 104 /g, for APC, I 17/g for coliform, 62/g for S. aureus and no growth for molds & yeasts. Salmonella was found in 20 of the raw samples. 950/0 of S. aureus isolates were coagulase positive. INHIBITION OF FOOD-BORNE PATHOGENIC BACTERIA BY GARLIC EXTRACTS. Sajida H. Ali* and KhalafS. AI-Delaimy*, Department of Food Science & Department of Biology, University of Baghdad, Baghdad, IRAQ. Water and ethanol extracts of garlic (Allium sativum L) were prepared and evaluated for their ability to inhibit various food-borne pathogenic bacteria. A concentration of 200-300 "I of water or ethanol extracts of garlic effectively inhibited Bacillus cereus, Staphylococcus aureus and Yersinia enterocolytica. Salmonella typhimurium was the least sensitive tested organism which needed > 400 "I of garlic extract for its inhibition. GROWTH AND ACID PRODUCTION BY LACTOBACILLUS SP IN THE PRESENCE OF EUGENOL. A.A. Adejumo* and G. Blank, Department of Food Science, University of Manitoba, Winnipeg, Manitoba R3T 2N2. Lactobacillus organisms isolated from fermented meat sausage were grown in an eugenol-based medium. Increasing concentrations of eugenol (.01 to .12% v/v) decreased both growth and titratable acidity, indicating lethality. Filtrates obtained from washed cells of these organisms grown in the presence of eugenol showed absorbancy at 260 and 280 nm, indicating leakage of intracellular components. Proteins and ATP were also shown to be some of the leakage products Cellular fatty acid analysis indicated a decrease in saturated fatty acids, and an increase in unsaturated and branched
Institute Affairs / xxxiii