###### Abstract  
The objective of this study was to evaluate the efficacy of gamma irradiation, applied to different cheese sample sizes (250g and 500 g), against _Listeria monocytogenes, Escherichia coli_, coliforms and aerobic colony counts. The effects on cheese physicochemical and odour properties and all costs involved for the treatment were quantified. The Cobalt-60 \(\gamma\)-irradiated was used at a maximum dose of 5.0 kGy. The values for cheese moisture (28.6%), ash (3.78%), pH (5.1), protein (29.6%), fat (30.7%), salt (1.95%) and water activity (0.92%) were within the acceptable ranges for hard cheese after gamma irradiation treatment. The colour (yellowness, redness, chroma and hue angle) and texture (cohesive-ness and springiness) values decreased (\(p<0.05\)) with the treatment. Compounds such as safrole, acetylpyrazine, thiophene, 3,5-ocuden-2-one and 1-Octen-3-one were present after the treatment, regardless of sample size. The gamma irradiation treatment resulted in 100%, 87.2%, 85.1% and 77.3% reduction in _L. monocytogenes_, coliforms, _E. coli_ and aerobic colony counts, respectively. The study highlighted the efficacy of irradiation treatment and its affordability for resource-limited producers. ab 2022  
Application of Gamma Irradiation Treatment on the Physicochemical and Microbiological Quality of an Artisanal Hard Cheese  
[PERSON], [PERSON], [PERSON], [PERSON], [PERSON], [PERSON], [PERSON], [PERSON], [PERSON], [PERSON]. Producers should be informed about alternative methods of improving food safety considering their financial ability. However, there is limited information on the practicality and affordability of using irradiation treatment, especially for small-scale artisanal cheese producers. This study will focus on gamma irradiation treatment applied on retail cheese sample sizes. Gamma irradiation is a process in which food products are exposed to ionising radiation in the form of gamma-rays in controlled dosages to destroy pathogenic microorganisms [4]. The ionising radiation is used to generate highly active chemical reactive species, including free radicals such as the hydroxy radical, and hydrogen peroxide, which react with microbial DNA, thereby killing or injuring food-spoilage bacterial organisms [7]. Food irradiation treatment does not cause adverse organoleptic changes or serious side effects when applied appropriately [8]. Higher doses of radiation have adverse effects on the sensorial and nutritional qualities. [PERSON] et al. [9] noted a significant increase in benzyl methyl sulfide and lipid oxidation, with doses over 7 kGy. On the other hand, several cheese types have been treated successfully with doses below 5 kGy to enhance their shelf-life and product safety, and these includes Palmita types of cheese Queso blanco [10], Karish [11] and Ras cheese [12]. [PERSON] et al. [13] also reported a dosage of 3 kGy to be effective in reducing _Staphylococcus_ spp., coliforms, yeasts and moulds in ice cream. Recently, other authors [14; 15] have also reported a significant reduction in microbial counts in foods after the gamma irradiation treatment. For food safety purposes, it is important to focus on eliminating spoilage and pathogenic microorganisms such as _Enterobacteriaceae_, _Listeria monocytogenes_, _Escherichia coli_ and coliforms on cheese products. Several types of artisanal cheeses are produced in South Africa and are characterised by a shorter ripening time of 90 days with a semihard consistency [2]. Most of these cheeses are from artisanal small-scale dairy plants. Appropriate treatment processes should be used in order to yield artisanal cheeses with improved health-promoting properties and consumer acceptance [16]. The specific objective of this study was then to evaluate the efficacy of gamma irradiation treatment applied to different cheese sample sizes of an artisanal pecorino-style cheese against _L. monocytogenes_, _E. coli_, coliforms and aerobic colony counts (ACCs).