A Rapid Metabolic Method for Predicting the Keeping Quality of Pasteurized Milk by High-Resolution Gas Chromatography

EFFECT OF SOME REFINING CONDITIONS ON TOTAL UNSAPONIFIABLES, STEROLS AND TOCOLS OF COTTONSEED OIL. A.A. EI-Nabyl, J.B. Rossell 2 and A.A.Y. Shehata l *, IDepartment of Food Science, University of Alexandria, Egypt; 2L.F.R. Association, Leatherhead, England. Bleaching removed 7.91Jfo of total unsaponifiables, 12% of total sterols and 4.51Jfo of total tocols from refined cottonseed oil. Deodorization under milder conditions (e.g. 22012 h) caused a further drop in unsaponifiables (10. 9IJfo), total sterols (10.1 lJfo) and total tocols (II lJfo), whereas under rigorous conditions (e.g. 300°CI2 h); unsaponifiables increased (25.4%), total sterols dropped (72.5IJfo) and total tocols dropped (70IJfo). Individual sterols, which were dominated by jJ-sitosterol (86.5IJfo) and compesterol (7.9IJfo), showed continued fall in their absolute levels with times and temperatures of deodorization, whereas their relative amounts remained essentially unchanged. Maximum losses of 60.21Jfo and 87.01Jfo in a-and "(tocopherols respectively occurred when deodorization was performed at 300°C for 2 h. FREEZE DRYING OF FRUITS AND VEGETABLES. D.C. Iwaniw and G.S. Mittal, School of Engineering, University of Guelph, Guelph, Ontario NIG 2WI. This paper provides an overall review of the freeze drying process applicable to the dehydration of various fruits and vegetables. This includes process modelling, process conditions, blanching methods and rehydration procedures. Emphasis is placed on the validation and limitations of various models and advantages and limitations of various processes. Many models for both heat and mass transfer have been developed, each derivation is different due to different physical conditions of each different system. Most fruits and vegetables to be freeze dried are frozen at or below -30°C. Maximum product temperatures range anywhere from _IO°C to 85°C while heater temperatures often reach temperatures well above 100°C. Chamber pressures range from 0.05 to 4.5 mm Hg. HEAT PRECIPITATION OF WHEY PROTEINS. A.R. Hill, Department of Food Science, University of Guelph, Guelph, Ontario NIG 2WI. The effects of heating pH (2.4 - 6.8) on thermal precipitation of proteins from sweet and acid wheys were studied. Ion exchange chromatography was used to measure residual whey proteins in isoelectric supernatants. At heating pH 4.6 - 6.8 precipitation of a-LA was greater in sweet whey than in acid whey, but at heating pH 2.4 3.4 there was no effect of whey variety on precipitation of a-LA. Heating at isoelectric pH (3.5 - 4.6) caused more precipitation of jJ-LG A than that of jJ-LG B in both acid and sweet wheys. Precipitation of a-LA at heating pH 2.4 - 3.5 was always greater than that of jJ-LG A and B but the reverse was true at pH 5.7 - 6.8. THE ROLE OF PROTEIN ENGINEERING IN FOOD RESEARCH - A REVIEW. R.L. Jackman* and R.Y. Yada, Department of Food Science, University of Guelph, Guelph, Ontario NIG 2WI. Developments in recombinant DNA (rDNA) technology have made selective alteration of primary amino acid sequences of proteins possible. Such manipulations using genetic engineering techniques have been referred to as protein engineering. Although this technology has seen only limited application in food research to date, this emerging and rapidly expanding technology offers exciting approaches to protein/enzyme modification studies, and may aid in the development of more functional and nutritious proteinaceous foods. This review outlines some basic protein engineering methodology and suggests how it has been used to advantage in the specific modification of enzymes, and the structure-function modification of various food proteins. FREEZING OF GROUND MEAT PRODUCTS. R. Hanenian and G.S. Mittal, School of Engineering University of Guelph, Guelph, Ontario NIG 2WI. This paper provides an overall review of the freezing of ground meat products. This includes prefreezing treatments; freezing methods such as air blast freezing, fluidized bed freezing, plate freezCall. Inst. Food Sci. Technof. J. Vol. 20, No.5, 1987

ing, immersion freezing; the effect of freezing rate on the meat quality; and the effect of repeated freeze-thaw cycles on product quality. TRANSPORT PROCESS MODELLING FOR THE FREEZING OF GROUND MEAT PRODUCTS. R. Hanenian and G.S. Mittal, School of Engineering, University of Guelph, Guelph, Ontario NIG 2WI. Over the past, an extensive amount of work has gone into the development of mathematical models for the food freezing times. Most of these models can be classified as analytical or numerical. An examination will be performed to determine the accuracy of some of the models in terms of predicting beef pattie freezing time. SINGLE-STEP PREPARATION OF COOKED CURED-MEAT PIGMENT AND ITS APPLICATION TO MEAT. R. Pegg* and F. Shahidi, Department of Biochemistry, Memorial University of Newfoundland, St. John's, Newfoundland AlB 3X9. A novel, single-step process for the preparation of the cooked cured-meat pigment, dinitrosyl ferrohemochrome (DNFH), from beef red blood cells is being developed. Beef red blood cells are converted to DNFH by the action of a nitrosating agent and a reductant in hot-alkaline aqueous solutions. Heat causes denaturation and detachment of the globin protein portion of the molecule which is either retained or may be separated from DNFH. Effect of DNFH, in either form, on the colour of cooked meats is under investigation. DNFH, in the isolated form or in the mixture with globin, may be stabilized by inclusion in jJ-cyciodextrin/gum arabic, followed by spray drying. A RAPID METABOLIC METHOD FOR PREDICTING THE KEEPING QUALITY OF PASTEURIZED MILK BY H1GHRESOLUTION GAS CHROMATOGRAPHY. B.H. Lee, Agriculture Canada Food Research Centre, Saint-Hyacinthe, Quebec J2S 8E3 and Department of Food Science & Agricultural Chemistry, Macdonald College of McGill University, Ste. Anne de Bellevue, Quebec H9X ICO. Gas chromatographic analyses of volatile and non-volatile metabolites were compared with microbial changes as an approach to the early detection of post-pasteurization contamination. Results obtained with the metabolic method using three different techniques (extraction, distillation, headspace) were compared with those recorded in the shelf-life test (standard: 106 bacteria/ml after 10 d at 7C) and the Moseley test (standard: 105 bacteria/ml after 5 d at 7C). From the results obtained, it was obvious that the greater the post pasteurization contamination by gram-negative bacteria, the lesser is the keeping quality. Some volatile and non-volatile compounds were unique as fingerprints while others were not.

LISTERIA MONOCYTOGENES IN RAW MILK SUPPLIES IN ONTARIO. P.J. Slade* and D.L. Collins-Thompson, Department of Food Science, University of Guelph, Guelph, Ontario NIG 2WI. The incidence of Listeria monocytogenes in Ontario raw milk supplies was investigated. Samples were plated directly onto McBride's (MB) agar, and onto Acriflavine Nalidixic acid (AN) agar, MB agar and Tryptose Agar (TA) after selective enrichment in nalidixic acidthiocyanate broth with acriflavine, at weekly intervals following coldenrichment in tryptose broth. Confirmation of isolates was based on the following characteristics: Henry's oblique transillumination, Gram-stain, catalase test, motility, fermentation of mannitol, rhamnose and xylose, and CAMP reaction. Results indicate about 5-lOlJfo of raw milk contains Listeria sp. THERMAL INACTIVATION OF YERSINIA IN FLUID MILK. C. Park*, Z. Stankiewicz and J.-Y. D'Aoust, Microbiol. Res. Div., Health Protection Branch, Health and Welfare Canada, Ottawa; D. Emmons, Food Research Centre, Agriculture Canada, Ottawa, Ontario. Incidents of human Yersinia enteritis can often be traced to the consumption of raw or underprocessed milk. Little information on thermal inactivation of Yersinia in fluid milk is available. We have studied the thermal effect on Yersinia in milk using a pilot-scale Abstract / 323