# Microbial Risk Assessment of Industrial Ice Cream Marketed in Italy
## 4 Discussion
The addition of ingredients post-pasteurization is of particular concern as there will be no other steps before marketing specifically designed to eliminate microbiological hazards that can contaminate the product. We could speculate that the results of the present study stress this criticality. A significantly greater load in aerobic colony count was found for the ice cream samples that had toppings or decorations compared to those that did not. In addition, the nine samples with unsatisfactory _Enterobacteriaceae_ values were all ice creams with inclusions contaminated after heat treatment, since these bacteria are usually killed by pasteurization if properly performed [45]. Against this background, the supply chain plays a key role in providing reliable ingredients. An effective supplier qualification system represents the first important instrument for manufacturers to produce high-quality and safe ice cream. Factors other than ingredients can contribute to the microbial contamination of the finished product, such as inadequate manufacturing practices and poor hygiene of the working environments. The manufacturing of ice cream involves several steps, some of which are particularly critical for its safety [6]. The first significant step is the storage of the raw materials, which must be kept at suitable temperatures, especially those that should be refrigerated, for which thermal abuse could favor microbial growth [46; 47; 48]. Once the ingredients have been weighed and blended, they are pasteurized. The success of the heat treatment ensures the inactivation of pathogenic microorganisms potentially present in the raw materials; therefore, accurate monitoring at this step is needed. Once pasteurized, the liquid mix is homogenized through a forced passage into small orifices, which serves to reduce the sizes of the fat globules. This process takes place after pasteurization, when the pasteurizer is of the batch type, while, in a continuous system, the homogenizer is usually placed before the heating section of the pasteurizer. The next step involves rapid cooling of the liquid mix, which is kept at \(\dashdot\)4 \({}^{\circ}\)C for a few hours up to a maximum of 24 h, to favor its ageing. Maintaining adequate temperatures during this step limits the growth of bacteria that have withstood pasteurization or recontaminated the mixture after the heat treatment. Then, the mix is pumped into the batch freezer, where it is extensively stirred while incorporating air, responsible for the typical soft texture of the ice cream. Moreover, airborne contaminations can occur [49]; therefore, air is usually microfiltered before being introduced into the batch freezer. The mixture from the batch freezer is dispensed into the final container and subjected to the hardening step inside wind tunnels or cold rooms, where it is further frozen without stirring. Any flavorings, colorings or inclusions, combined with the mix within the batch freezer or before the hardening step, are added either manually or through separated extruders. From the batch freezing step to packaging, ice cream undergoes a gradual freezing process that stops microbial growth. Compliance with the cold chain during storage of the finished product is critical for the ice cream itself, even before its safety. Indeed, the refrigeration temperatures necessary to allow microbial growth would completely melt the ice cream. Therefore, it is clear that the real risk is represented by contamination with high microbial loads, such as for the three ice creams contaminated by levels of _L. monocytogenes_ beyond the acceptability limits, or if the contamination occurs by pathogenic microorganisms with a very low minimum infectious dose, such as some strains of _Salmonella_ spp. [37]. In addition to the ingredient, contamination during production can occur through the workforce, plants and equipment; therefore, a comprehensive approach to the whole production system is needed to guarantee safe and high-quality ice cream.