Nowadays, agro-industries are trying to reduce their impact on the environment by reducing waste, natural resources consumption and by entering in a circular bio-economy logic. Cleaning and disinfection, as mandatory for food safety requirements, are considered to be among the most demanding operations in terms of energy, water and chemical with non-negligible impacts on the environment. The FairChain project is a European project aiming to achieve food systems that are more sustainable from an environmental, social and economic perspective. One of the studied cases concerns the potential uses of vinegar produced from pomaces, co-product from apple juice, including cleaning and disinfection. In this study, we investigated whether vinegar could be used during the Cleaning in Place (CIP, (60°C, 10 min, 3.60 Pa) procedure to inactivate and/or remove Bacillus adherent spores and vegetative cells from stainless steel. We used a commercial vinegar (5, 8, 14 and 20%) and the one produced for the FairChain project (8% equivalent acetic acid). The efficiency of water alone (rinsing) was also tested, to determine the role of the mechanical effect of flow during the CIP procedure. Coupons were first contaminated with spores of Bacillus subtilis PY79 (hydrophilic) or of the mutant B. subtilis PY79 ΔspsI (hydrophobic), subjected to the rinsing and CIP procedures and the amount of residual CFU was estimated. Our results first failed to demonstrate any disinfectant effect of vinegars on both spores. On hydrophilic spores, for all but 20% vinegar, the effectiveness of CIP was not significantly different to that of water (+/- 3 log reduction), suggesting a predominant mechanical effect. For the 20% vinegar, an additional effect of 0.2 log reduction was observed, which suggests a slight chemical effect in addition to the mechanical effect on the spore detachment. Concerning the hydrophobic spores, only the most concentrated vinegars (14% and 20%) proved more effective (0.87 and 0.96 log reduction, respectively) than water alone (0.17 log reduction).
Similar experiments were performed on vegetative cells of B. cereus 98/4, a strain isolated from an industrial site. A major disinfectant effect of vinegars was revealed with a 2-log reduction of viable cells by FairChain vinegar, for example. In dynamic conditions, an additional 1-log reduction was observed for the different vinegars, probably resulting from the mechanical effect due to the flow. We can therefore conclude that 1/ high concentrations of vinegar improved the cleaning of Bacillus spores, 2/ the FairChain vinegar did not promote a significant spore detachment during CIP procedures, 3/ the FairChain vinegar is efficient in disinfecting contaminated surfaces with Bacillus cells We will pursue the study by i) studying the effect of vinegar on hydrophobic spore surface (crust composition and structure) to explain the suspected cleaning effect ii) identifying all the potencies in hygiene of the FairChain vinegar to follow a circular economy logic while using more ecofriendly cleaning produces.