The effect of changing the tinplate thickness of food cans on the process lethality given to low acid, canned food products

Thesis (MSc)--Stellenbosch University, 2025.

Featherstone, S. 2025. The effect of changing the tinplate thickness of food cans on the process lethality given to low acid, canned food products. Unpublished masters thesis. Stellenbosch: Stellenbosch University [online]. Available: https://scholar.sun.ac.za/items/fa6a0970-44f0-4272-81e2-d3d30c1cd1b0

ENGLISH ABSTRACT: This thesis investigates the impact of tinplate thickness on the thermal processing of canned foods, specifically focusing on whether changes in can specifications affect heat penetration rates, thereby influencing the safety and processing conditions of food products. The study tested the hypothesis that altering the thickness of tinplate in food cans does not affect the rate of heat penetration into the product, which would imply that processing conditions could remain constant regardless of tinplate thickness. Three different tinplate thicknesses (0.13 mm, 0.17 mm and 0.23 mm) were evaluated using both conduction and convection heating processes at temperatures of 116°C and 121°C. The products chosen for testing were tomato purée, for conduction heating, and water, for convection heating. The results showed that for the conduction heating scenario at 121°C, there was a statistically significant difference in heating rates related to tinplate thickness (p-value = 0.034), with the thinnest tinplate showing the fastest heat penetration. However, for other scenarios, no statistically significant differences were observed, temperature profiles and descriptive statistics indicated variations. The study used cans from two manufacturers with differences in tinplate thickness, can structure (beaded vs. straight-walled) and manufacturing technologies (welded flat sheet tinplate and Drawn and Wall Ironed (DWI). The differences in heating rates were more pronounced with conduction products compared to convection, and more pronounced at the higher process temperature (121°C) compared with the lower process temperature (116°C). Limitations included the use of multiple types of temperature measuring devices (TMDs) due to cost constraints, which might have influenced data variability. Future research could explore the impact of can beading designs on internal convection currents and the effects of tinplate thickness with more viscous, solid food products. The results of the study suggests that when changing suppliers or can specifications, food processors should consider revalidation of the thermal processes to ensure product safety and quality. Although the differences in heating rates among the three can variables were minor, this study underscores the necessity for a thorough understanding of the products and packaging being processed as seemingly minor changes could result in a under-processing incident in some cases.

AFRIKAANSE OPSOMMING: Hierdie tesis ondersoek die impak van blikplaatdikte op die termiese verwerking van ingemaakte voedsel, en fokus spesifiek op die vraag of veranderinge in blikspesifikasies hittepenetrasietempo's beïnvloed, en sodoende die veiligheid en verwerkingstoestande van voedselprodukte beïnvloed. Die studie het die hipotese getoets dat die verandering van die dikte van blikplaat in voedselblikkies nie die tempo van hittepenetrasie in die produk beïnvloed nie, wat sou impliseer dat verwerkingstoestande konstant kan bly ongeag die blikplaatdikte. Drie verskillende blikplaatdiktes (0.13 mm, 0.17 mm and 0.23 mm) is geëvalueer deur beide geleiding- en konveksieverhittingsprosesse by temperature van 116°C en 121°C te gebruik. Die produkte wat vir toetsing gekies is, was tamatiepuree, vir geleidingsverhitting, en water, vir konveksieverhitting. Die resultate het getoon dat vir die geleidingsverhittingscenario by 121°C, daar 'n statisties betekenisvolle verskil in verhittingstempo's was wat verband hou met blikplaatdikte (p-value = 0.034), met die dunste blikplaat wat die vinnigste hittepenetrasie toon. Vir ander scenario's is geen statisties betekenisvolle verskille egter waargeneem nie, temperatuurprofiele en beskrywende statistieke het variasies aangedui. Die studie het blikkies van twee vervaardigers, gebruik, met verskille in blikplaatdikte, blikstruktuur (gegolfde vs. reguitwandige) en vervaardigingstegnologieë (gelaste platplaatblikplaat en Drawn and Wall Ironed (DWI). Die verskille in verhittingstempo's was meer prominent met geleidingsprodukte in vergelyking met konveksie, en meer prominent by die hoër prosestemperatuur (121°C) in vergelyking met die laer prosestemperatuur (116°C). Beperkings het die gebruik van veelvuldige tipes temperatuurmeettoestelle (TMD's) ingesluit as gevolg van kostebeperkings, wat dataveranderlikheid kon beïnvloed het. Toekomstige navorsing kan die impak van blikgolf-ontwerpe op interne konveksiestrome en die uitwerking van blikplaatdikte met meer viskose, soliede voedselprodukte ondersoek. Die resultate van die studie dui daarop dat wanneer hulle van verskaffers of blikkiespesifikasies verander, voedselverwerkers die hervalidering van die termiese prosesse moet oorweeg om produkveiligheid en kwaliteit te verseker. Alhoewel die verskille in verhittingstempo's tussen die drie blikkiesveranderlikes gering was, beklemtoon hierdie studie die noodsaaklikheid van 'n deeglike begrip van die produkte en verpakking wat verwerk word, aangesien oënskynlik geringe veranderinge in sommige gevalle 'n onderverwerkingsvoorval tot gevolg kan hê.

Masters