PACKAGING TECHNOLOGY AND SCIENCE Packag. Technol. Sci. 2005; 18: 53–57 Published online 1 February 2005 in Wiley InterScience (www.interscience.wiley.com). DOI:10.1002/pts.672 Technical Note – the Significance of Chuck Wall Angles in the Quantification of Seam Thickness in Canned Food By Å.Vågane, 1 S. Birkeland, 1 E.Wasbø 2 and M. Sivertsvik 1* 1 Norconserv AS, Seafood Processing Research, Niels Juelsgate 50, PO Box 327, NO-4002 Stavanger, Norway 2 Norwegian University of Science and Technology, Department of Physics, NO-7491 Trondheim, Norway One of the key dimensional measures in quality control of canned foods is the double seam thickness (mm). Electronic micrometers quantify the seam thickness, based on a chuck wall angle of 4.0° due to the seaming chuck being fixed at the same angle during seaming. Investigations of chuck wall angles (n = 144) in non- round cans by a coordinate measuring machine revealed that 93% of the chuck wall angles following seaming were off the interval 4.0 ± 0.25° (range: 3.146–10.281°, CV = 23%), indicating that the seaming process introduces a significant variance in the chuck wall angle. The aberration in the actual chuck wall angle from 4.0° introduces a bias (e) in the measured seam-thickness ( T ms ), which may cause rejection of closed cans as having unacceptable seam thickness based on incorrect measurements. The mathematical deduction of the bias introduced in the measured seam thickness when the actual chuck wall angle is aberrant from 4.0° is presented, and it is concluded that it is erroneous to neglect the chuck wall angle of sealed cans in the methodology of seam thickness determination. Copyright © 2005 John Wiley & Sons, Ltd. Received 3 September 2004; Revised 28 September 2004; Accepted 1 October 2004 KEY WORDS: canned foods; seaming; double seam; seam thickness; chuck wall angle * Correspondence to: M. Sivertsvik, Norconserv AS, Seafood Processing Research, Niels Juelsgate 50, PO Box 327, NO-4002 Stavanger, Norway. Email: ms@norconserv.no Copyright © 2005 John Wiley & Sons, Ltd. INTRODUCTION Package integrity of canned foods is vital, and an important element in the production of safe, wholesome and good quality canned products is that each can meets certain recognized standards. Such standards include defects with respect to the can profile, double seam, side seam, can end, can body, physical abuse and handling. Occasionally, the can integrity, and thus these standards, is com- promised by various defects of different origin. The defects may arise throughout the various stages of can manufacture, transport, filling, closing, processing and handling before the can reaches the consumer. For producers of canned products, the closure (i.e. double seam formation) of the cans is of key importance. For heat-processed foods in sanitary cans, the seam has to be hermetic, i.e. absolutely impervious to air or flow of material in any direc- tion. 1 The double seam consists of five layers of plate and a sealing compound (Figure 1) and is defined as the joint formed between the can body and the can end by the mechanical interlocking and compression of the can flange and the end curl.