Document LKQLzLZEZzQRgQ6ZzV1439eG5

I Film Man jeturers' Association Secretarial: Peat, Marwick, Mitctiall & Co. Telaohona: (0742) 751234 Talax: 54170 Telegram*: Veritatem Sheffield Prof. Dr. A. Hildebrandt Bundesgesundheitsamt Postfach 330013 D-1000 Berlin 33 West Germany spy p. 0. Box 121. The Fountain Precinct. 1 Balm Green, SHEFFIELD. SI 3AF. 10th May, 1985 Dear Professor Hildebrandt, Enclosed are the NATEC microbiollo,gical results previously mentioned to you. In the event, these resultjs do not reflect the common experience in retail distribution of fresh meat, which is that flexible PVC is superior to any polyolefinic fillm so far available for stretch-wrapping. We were initially at a loss to explain the differences between academic studies conducted at Kulmbach aid NATEC on the one hand and commercial experience on the other, even allowing for adequate oxygen permeability of the polyolefinic films. The difference, we now believe, lies in a combination of pack to meat volume ratio and in the large d fference in water vapour permeability rates between flexible PVC and ;lolyolefinic films. In the NATEC work, the meat was at all times out o contact with the films. We believe the same was substantially true of the Kulmbach work. In commercial practice, meat pi aced upon a paper or expanded polystyrene tray and overwrapped with film fill result in a wide variety of pack profiles, many of which have th film in contact with the upper surface of the meat. Such packs also ha,1 ve little free volume between film and the sides of the meat. The result is that exuded flui ds are trapped between meat surface and film. In the case of contact vjith polyolefinic films, the water vapour permeability of which is low - see attachment No. 1 - water activity of the meat (commonly designated ) remains in the region of 1.30. At this level of a , all spoilage Bacteria can multiply. In the case of meat packaged w: th flexible PVC film whose water vapour permeability is five times higt er than that of polyolefinic films, we surmise that the af falls the imall amount needed - a = 0.91^0-95 (see attachment No: 2) to dras '.ically reduce the growth rate of spoilage bacteria. The effect is enhanced by the fact that the permeability of liquid water through flexible PVC is about 20% higher than that for vapour alone, whsreas values for polyolefines are independent of the nature of the water pnase. /cent.. SPI-00834 1 Attachment No. 3 discusses the gen1 in food packaging. We have further work ln-hand to Illustrate this hypothesis and have already shown that the rate ojf development of total volatile nitrogen (TVN) in a meat pack is function of the ratio (meat volume/ pack volume), though the work is yet incomplete. See attachments Nos. 4 and 5. TVN is of course Imeasure of protein degradation due to bacterial activity. The performance in the NATEC repo t of the flexible PVC film formulated with polymeric plasticiser replac|L,ng part of the DOA (sample B2 or II), coupled with its only slightly rejduced water vapour transmission rate (76 vs 94 gn/m1 24 hrs) leads us to believe that such a film may also perform adequately in most cases certainly better than polyolefinics. Its migration rate into meat wou also be significantly lower than from traditional films. We would remind you also that thfe particular suitability of flexible PVC in commercial terms based uppn physical properties such as cling, elasticity, clarity, puncture resistance and general pack appearance remains an important factor. You have agreed that users' opinions should be established "on neutral ground" as recorded in your Minutes of the meeting 27th February 1934. We shall be pleased to co-operate in this. Yours faithfully, /w Secretaries SPI-00835