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Chrysanthi Champidou, Ph.D. student at Secalim, in the framework of a collaboration with Nestlé, presented her doctoral work on the thermal inactivation of Bacillus licheniformis spores in plant-based bovine milk and broth.

Chrysanthi Champidou¹, Mariem Ellouze¹, Nabila Haddad² et Jeanne-marie Membre²

1. Nestlé, Lausane, Suisse

2. Oniris, INRAE, SECALIM, France

Abstract:

Introduction: The consumer demand for plant-based milk alternatives has been increasing in the last years. The potential food spoilage induced by spore-forming bacteria from plant-based ingredients is an emerging research topic.
Purpose: The objective of the present study was to characterize the thermal inactivation of spores of spoilage organisms in plant-based and bovine milk and assess the potential protective matrix effect.
Methods: Bacillus licheniformis was chosen as a model microorganism due to its common involvement in spoilage incidents in milk and vegetables. To investigate the impact of food matrix on the inactivation profile of spores, experiments were carried out in several plant-based milk alternatives, half-skimmed bovine milk and BHI broth, used as a reference. B. licheniformis CTCPA 3107001 spores were inoculated to the selected matrices with an initial concentration of 9 log CFU/mL. Samples were subjected to heating at five different temperature levels, 97.5, 100, 102.5, 105 and 110°C, following the methodology of thermal treatment with capillary tubes in an oil bath. All matrix/temperature combinations were analyzed in biological triplicates.
Results: In BHI broth, inactivation followed a linear trend, however, the kinetics obtained in food products included shoulders and tails. Thus, the linear regression model fitted to the data showed non-satisfactory goodness of fit; therefore, non-linear models were fitted. In addition, the inactivation parameter estimates revealed differences between the various plant-based milk alternatives, indicating the need for more precise inactivation assessments to fully characterize spore inactivation in these products.
Significance: This study is of a great importance since, to the best of our knowledge, it is the first attempt to describe inactivation kinetics of spore-forming bacteria in plant-based milk alternatives and can contribute to the reduction of spoilage incidents, hence, major financial losses for the food industry globally.

Antoine Gaillac, Ph.D student at SECALIM, presented the progress of his thesis work on the exploration of the diversity of biofilm formation by the food bacterium Brochothrix thermosphacta and its ability to form biofilms on industrial food surfaces.

Abstract:

Introduction: Biofilms play an important role in residence and persistence of microorganisms in the food industry. Brochothrix thermosphacta is considered as a major food spoiler (Illikoud et al., 2019). This bacterium has been identified in biofilms on multiple surfaces of the food processing environment (Wagner et al., 2020, 2021).
Purpose: The biofilm formation ability and the biofilm structural diversity of 30 multi-origin B. thermosphacta strains has been explored. Also, to simulate the food industrial environment conditions, the high biofilm producer strain CD337(2) was cultivated in a CDC biofilm reactor on polycarbonate (PC), polystyrene (PS) and stainless steel (SS) surface coupons.
Methods: The biofilms were analysed using a set of complementary biofilm assays (biofilm ring test, crystal violet staining, confocal laser scanning microscopy and BiofilmQ images analysis software). The biofilms on coupons were analysed with plate counting, specific rpoC-qPCR, confocal laser scanning microscopy and BiofilmQ.
Results: Two major groups corresponding to low and high biofilm producers were identified. High biofilm producers presented flat architectures characterized by high surface coverage, high biofilm volume, and high surface area (Gaillac et al 2022). Biofilm growth on those three surfaces show similar kinetics. However, highly structured biofilm was observed on PC and PS instead of flat biofilm observed on SS. The biofilm on the SS coupons show a higher biofilm outer surface area per volume unity, contact area of the biofilm to the substrate and percentage of substratum covered by microbial cell compared to biofilms on PC and PS coupons. Conversely, a lower biofilm density and a lower biofilm volume per substrate area unity was highlighted from biofilm on the SS coupons.
Significance: Ability to form biofilm on food industrial surfaces, with various structures, suggests a strong ability of B. thermosphacta to persist in the food manufacturing environment.

Rodney Feliciano recently defended his PhD thesis that he carried out within SECALIM in the framework of the European project ITN Protect. He presented his thesis work on the effects of climate change on dairy farming in the Middle East: Insights on microbiology and raw milk quality.
Rodney Feliciano¹, Géraldine Boué¹, Mohammed Mustafa Hussaini², Fahad Mohssin², Jeanne-Marie Membré¹
1. Oniris, INRAE, SECALIM  

2. AlSafi Danone

Abstract:

Dairy farms in the Middle East are characterized by highly mechanized intensive farms producing large quantities of raw milk despite unfavourable weather conditions. On the other hand, climate change threatens dairy farms by altering raw milk quality and initiating cow heat stress. Thus, farms from hot weather conditions can hold potential insights that may aid with the preparation for climate change. However, relatively few information is available from these farms, and as such, a largescale intensive dairy farm from Saudi Arabia was analysed. Therefore, the objective of this study is to analyse the multivariable raw milk quality control dataset using a modelling strategy.
The correlation analyses have shown interesting one-at-time correlations between physicochemical properties, microbial counts, and environmental variables. Next, Principal Components Analysis determined a low data structure but identified seasonal patterns and associated key variables. However, the microbial counts cannot be fully explained by seasonal environmental conditions. This shows that in terms of microbial food safety, a great deal of information might be lost by only focusing on raw milk quality. Lastly, Partial Least Squares regression was used to predict %protein and %fat while highlighting the interrelationships between physicochemical parameters. Overall, it was demonstrated that in order to prepare for climate change, maximum information can be gained if data from other departments be collected for analysis. Furthermore, the modelling strategy used in this study can be applied to other food systems and aid future researchers in preparing for the effects of climate change.

Francis Lauriau, veterinary public health inspector and doctoral student at SECALIM presented a poster on the potential effect of the drenching step in poultry slaughterhouses on the control of Campylobacter.

Francis Lauriau, Sofia Strubbia, Jean-Michel Cappelier, Nabila Haddad et Sandrine Guillou

Oniris, INRAE, Oniris

Abstract:

Introduction: Campylobacter is the most common bacterial foodborne pathogen in Europe, mainly associated with poultry meat consumption. To mitigate the campylobacteriosis risk and reduce the contamination level of Campylobacter in poultry carcasses, measures can be taken on the farm but also at the slaughterhouse.
Purpose: Based on two real industrial situations where the levels of Campylobacter contamination at the end of slaughtering were contrasted, the objective of this study was to identify the critical slaughtering stages which could explain these differences.
Methods: Two French slaughterhouses were selected because of their difference in Campylobacter prevalence not complying with the EU Regulation, while their slaughter process was otherwise similar. Between October and December 2022, nine batches over three slaughter days were sampled at each slaughterhouse. Caeca, as well as neck skins at the end of plucking, final rinse after evisceration, and chilling stages, were collected for Campylobacter enumeration.
Results: From caecal contents with not significantly different levels of Campylobacter contamination in the two slaughterhouses, lower levels of Campylobacter on the neck skin at the end of slaughter were found in slaughterhouse A (SA) (1.9 ± 1.1 log CFU/g) than in slaughterhouse B (SB) (2.8 ± 1.1 log CFU/g). The highest decrease in Campylobacter contamination level on neck skins from the plucking to the chilling stage in SA (-0.89 ± 0.54 log CFU/g) than in SB (-0.05 ± 0.39 log CFU/g), could be mainly attributed to chilling, resulting in a decrease of 0.68 ± 0.54 log CFU/g in SA, compared to only 0.18 ± 0.29 log CFU/g in SB.
Significance: This study highlights that acting at the slaughterhouse and more specifically at the chilling stage could represent a potential lever to reduce Campylobacter levels in broiler carcasses. The influence of factors influencing survival of Campylobacter under cold and dry stress still needs to be investigated for chilling optimization.