Dairy Manufacturing Plants Research Articles

The Use of Ozone as an Eco-Friendly Strategy against Microbial Biofilm in Dairy Manufacturing Plants: A Review.

Managing spoilage and pathogenic bacteria contaminations represents a major challenge for the food industry, especially for the dairy sector. Biofilms formed by these microorganisms in food processing environment continue to pose concerns to food manufacturers as they may impact both the safety and quality of processed foods. Bacteria inside biofilm can survive in harsh environmental conditions and represent a source of repeated food contamination in dairy manufacturing plants. Among the novel approaches proposed to control biofilm in food processing plants, the ozone treatment, in aqueous or gaseous form, may represent one of the most promising techniques due to its antimicrobial action and low environmental impact. The antimicrobial effectiveness of ozone has been well documented on a wide variety of microorganisms in planktonic forms, whereas little data on the efficacy of ozone treatment against microbial biofilms are available. In addition, ozone is recognized as an eco-friendly technology since it does not leave harmful residuals in food products or on contact surfaces. Thus, this review intends to present an overview of the current state of knowledge on the possible use of ozone as an antimicrobial agent against the most common spoilage and pathogenic microorganisms, usually organized in biofilm, in dairy manufacturing plants.

Evaluating the Temperature of Incoming Raw Milk at a Dairy Processing Plant

Ensuring stringent temperature control parameters and efficient cooling mechanisms are maintained at a dairy plant are critical to downstream processing capabilities and product quality. This study examined the temperature of incoming raw milk across three production months (June, July, August 2018), to capture peak season processing at one dairy manufacturing plant. A total of n=4,236 data points across three milk intake bays were analysed.Across the study area, the average temperature of incoming milk was 6.18°C (1.54 Standard Deviation (SD)). After the initial cooling step in the dairy facility, the average temperature of stored

Evaluation of lactose oxidase as enzymatic antifungal control for Penicillium spoilage in yogurt

In this study, we investigated the antifungal activity of lactose oxidase (LO) as a potential biopreservative in dairy products. Our study objectives were to screen antifungal activity of LO against common mold strains, to detect the minimum inhibitory level of LO against the same strains, and to understand how LO affects the pH and lactic acid bacteria (LAB) counts in set yogurt. Five mold strains (Penicillium chrysogenum, Penicillium citrinum,Penicillium commune,Penicillium decumbens,and Penicillium roqueforti) were used throughout study. These strains were previously isolated from dairy manufacturing plants. Throughout the study, yogurts were stored at 21 ± 2°C for 14 d. Antifungal activity of LO was screened using 2 enzyme levels (1.2 and 12 g/L LO) against selected strains on the surface of a miniature laboratory set-yogurt model. For all tested strains, no visible mold growth was detected on the surface of yogurts covered with LO compared with control yogurt without LO. The minimum inhibitory level of LO against each strain was further investigated using 4 enzyme levels (0.12, 0.48, 0.84, and 1.2 g/L LO) on the miniature laboratory set-yogurt model. We detected 0.84 g/L LO as the minimum level inhibiting visible hyphal growth across strains. The minimum inhibitory level of LO varied for each individual strain. To study the effect of LO on the pH of yogurt, miniature laboratory set-yogurt models were covered with different enzyme levels (0.12, 0.48, 0.84, 1.2, and 12 g/L LO). At d 14, a difference was detected comparing pH values of treatments to control with no LO. Commercial low-fat set yogurt was used to study the effect of LO on LAB survival when yogurt surface was covered with 0.84 g/L LO under the same experimental conditions. Control with no LO was included. At d 14, 3 levels of catalase were added (0, 0.01, and 0.1%) to each treatment. To enumerate LAB, homogenized samples were plated on de Man, Rogosa, and Sharpe agar and incubated. Yogurts with 0.84 g/L LO had lower LAB counts compared with control yogurts, and catalase level did not have a significant effect on LAB counts. Our results demonstrated potential antifungal efficacy of LO against common spoilage organisms in dairy products with residual lactose and relatively low pH. Manufacturers should establish efficacy of LO against mold strains of interest and determine the effects of LO on organoleptic properties and LAB survival in set yogurt.

Heterogeneous response of Geobacillus stearothermophilus biofilms to calcium

Geobacillus stearothermophilus contamination of milk powder products originates from bacteria released from biofilms in dairy manufacturing plants. Calcium, a major component of milk minerals, was previously found to affect G. stearothermophilus biofilm growth on surfaces exposed to milk formulations. This study endeavoured to reproduce the effect of calcium on biofilm formation of several G. stearothermophilus dairy isolates and one reference strain in modified TSB media and gain more insights into the role of calcium in biofilm formation of G. stearothermophilus. Calcium presence increased biofilm cell numbers of strain A1, but reduced cell numbers of the reference strain and showed no significant effect on strain P3. The quantity of extracellular polymeric substances (EPS), in particular extracellular protein, varied between strains. Unlike the consistent effect of calcium in milk formulations found previously, current findings suggest that strain to strain differences exists in biofilm formation of G. stearothermophilus in the presence of calcium.

A comparison of analytical test methods in dairy processing

Dairy quality strategies start at the beginning of a raw milk supply chain at farm level, but it is the obligation of the manufacturer at a dairy processing plant to ensure quality is upheld from intake to finished product. This is achieved by implementing robust quality systems, measured through sampling plans and analytical test methods. Influences on product quality and composition, and analytical test results within a dairy plant are multi-factorial including: seasonality; the quality of incoming milk and herd health; the level of skilled laboratory technicians; the level of production and the availability of equipment; and finally milk harvesting, transportation and handling. These factors, along with customer and regulatory requirements will determine the level and type of analytical testing required. In the dairy industry, manufacturers oftentimes pay little attention to the need for optimising analytical test strategies or improving laboratory operations, if it is not broken why fix it? The focus of this qualitative research was to differentiate the core current analytical test methods in use at three dairy manufacturing plants for the production of raw milk, skim milk and cream and skim milk powder (SMP). The main objective being to inform and educate each producer on best practice methods. Results displayed similarities across testing categories but demonstrated a range of traditional testing methods in the microbiological analysis compared to advanced instrumentation use in the chemical and compositional analytical category. The dairy industry needs to adapt to a modern, process focused quality system using industry 4.0 analytical processing regimes.

Identification and selection of heat-stable protease and lipase-producing psychrotrophic bacteria from fresh and chilled raw milk during up to five days storage

The quality of raw milk is important in determining the quality of manufactured dairy products. In recent years, the amalgamation of small dairy manufacturing plants into large mega sites has resulted in longer storage of milk during transportation and storage, particularly during peak milk flow in a seasonal dairy industry. The aim of this research is to determine the influence of this extended storage on psychrotrophic enzyme-producing bacteria even if the cold chain is maintained. In this study, the numbers and types of psychrotrophs in raw milk with and without refrigerated enrichment (5 days at 7 °C) were compared to understand the effect of extended refrigeration on the changes in raw milk microbial ecology. Two-hundred and six isolates from both fresh and enriched raw milk were identified by MALDI-TOF MS and assessed for proteolytic and lypolytic activity at 7 °C and the heat stability of these enzymes (72 °C, 15 s) was measured. This is the first report to compare the raw milk microbiota before and after extended refrigeration at both genus and species levels. This study also characterized these bacterial isolates, some of which have never been reported in milk, for their potential to spoil dairy products.

Role of Bacillus species in biofilm persistence and emerging antibiofilm strategies in the dairy industry.

Biofilm-forming Bacillus species are often involved in persistent contamination and spoilage of dairy products. They therefore present a major microbiological challenge in the field of dairy food quality and safety. Due to their substantial physiological versatility, Bacillus species can survive in various parts of dairy manufacturing plants, leading to a high risk of product spoilage and potential dissemination of foodborne diseases. Furthermore, biofilm and heat-resistant spore formation make these bacteria challenging to eliminate. Thus, some strategies have been employed to remove, prevent, or delay the formation of Bacillus biofilms in the dairy industry, but with limited success. Lack of understanding of the Bacillus biofilm structure and behavior in conditions relevant to dairy-associated environments could partially account for this situation. The current paper reviews dairy-associated biofilm formation by Bacillus species, with particular attention to the role of biofilm in Bacillus species adaptation and survival in a dairy processing environment. Relevant model systems are discussed for the development of novel antimicrobial approaches to improve the quality of dairy food. © 2020 Society of Chemical Industry.

Quantifying the uncertainty of transfer of Cronobacter spp. between fomites and floors and touch points in dairy processing plants

Cronobacter spp. are opportunistic pathogens that must be controlled in infant powder manufacturing plants. This study evaluated the spread of Cronobacter cells via contact surfaces within a dairy manufacturing environment. Transfer rates of Cronobacter spp. were determined from vectors for transmission including moveable fomites (e.g. trolley wheels and boots) and gloved hands to various types of recipient surfaces (stainless steel, linoleum and resin-coated concrete) typical for dairy manufacturing environments. Overall, with a starting inoculum of 106 CFU/mL, approximately 104 CFU/mL Cronobacter cells were transferred from each fomite onto each recipient surface during the initial transfer event. Gloved hands transferred the highest number of Cronobacter cells, followed by polyvinylchloride boots and then polyurethane trolley wheels. We demonstrate, using a combination of experimental data and uncertainty analysis, that if a movable fomite (boots or trolley wheels), or gloves became contaminated, Cronobacter could be spread over a wide area within a manufacturing plant. To the authors’ knowledge, this is the first quantitative estimation of the spread of Cronobacter within a dairy manufacturing plant, that can also be practically applied as a tool for providing information in making risk management decisions. In particular, the estimation of spread suggests areas for cleaning and sanitation within a dairy manufacturing environment during a contamination event.

Resistance of thermophilic spore formers isolated from milk and whey products towards cleaning-in-place conditions: Influence of pH, temperature and milk residues

The occurrence of thermophilic spore formers in dairy powders is a major concern for producers worldwide. This study aims to investigate the resistance of thermophilic endospores towards cleaning solutions typically used for cleaning-in-place in dairy manufacturing plants. From eleven tested strains, all were able to survive an alkaline treatment (NaOH) at 65 °C for 10 min (0.5%), whereas at concentrations of 2% eight strains withstood the treatment. Acid solutions were more sporicidal. At 0.5% of HNO3, only three strains survived the treatment. Milk impurities reduced the inactivation effect of the NaOH solutions towards thermophilic spore formers. For two selected strains, a detailed kinetic inactivation in NaOH and HNO3 solutions at different temperatures was performed and non-log-linear inactivation curves were observed. This study highlights the risk of reusing cleaning solutions in dairies.

Propensity for biofilm formation by aerobic mesophilic and thermophilic spore forming bacteria isolated from Chinese milk powders

Biofilms on the surface of dairy manufacturing plants are potential reservoirs of microbial contamination. These microbial aggregates may harbour pathogenic and spoilage organisms which contaminate dairy products. The biofilm forming capacity of many spore forming isolates of dairy origin has not been given much attention. The present study explored the biofilm forming potential of 148 isolates, comprising mesophilic and thermophilic bacteria, with particular emphasis on Bacillus licheniformis on polystyrene and stainless steel (SS) surfaces. We concluded that only four species are of significance for biofilm development on the surface of SS in the presence of skimmed milk, namely, B. licheniformis, Geobacillus stearothermophilus, Geobacillus thermoleovorans group and Anoxybacillus flavithermus. The maximum number of cells recovered from the biofilms developed on SS coupons in the presence of skimmed milk for these four species was as follows: 4.8, 5.2, 4.5 and 5.3logCFU/cm2, respectively. Number of cells recovered from biofilms on 1cm2 SS coupons increased in the presence of tryptic soy broth (TSB) for all mesophiles including B. licheniformis, while decreased for G. stearothermophilus, G. thermoleovorans group and A. flavithermus. The crystal violet staining assay on polystyrene proved to be inadequate to predict cell counts on SS for the bacteria tested in our trial in the presence of either TSB or skimmed milk. The results support the idea that biofilm formation is an important part of bacterial survival strategy as only the most prevalent isolates from milk powders formed good biofilms on SS in the presence of skimmed milk.Biofilm formation also proved to be a strain-dependent characteristic and interestingly significant variation in biofilm formation was observed within the same RAPD groups of B. licheniformis which supports the previously reported genetic and phenotypic heterogeneity within the same RAPD based groups. The work reported in this manuscript will broaden our knowledge on biofilm formation of a large number of dairy isolates and emphasize strain and substrate dependence.

Insights into the Geobacillus stearothermophilus species based on phylogenomic principles

BackgroundThe genus Geobacillus comprises bacteria that are Gram positive, thermophilic spore-formers, which are found in a variety of environments from hot-springs, cool soils, to food manufacturing plants, including dairy manufacturing plants. Despite considerable interest in the use of Geobacillus spp. for biotechnological applications, the taxonomy of this genus is unclear, in part because of differences in DNA-DNA hybridization (DDH) similarity values between studies. In addition, it is also difficult to use phenotypic characteristics to define a bacterial species. For example, G. stearothermophilus was traditionally defined as a species that does not utilise lactose, but the ability of dairy strains of G. stearothermophilus to use lactose has now been well established.ResultsThis study compared the genome sequences of 63 Geobacillus isolates and showed that based on two different genomic approaches (core genome comparisons and average nucleotide identity) the Geobacillus genus could be divided into sixteen taxa for those Geobacillus strains that have genome sequences available thus far. In addition, using Geobacillus stearothermophilus as an example, we show that inclusion of the accessory genome, as well as phenotypic characteristics, is not suitable for defining this species. For example, this is the first study to provide evidence of dairy adaptation in G. stearothermophilus - a phenotypic feature not typically considered standard in this species - by identifying the presence of a putative lac operon in four dairy strains.ConclusionsThe traditional polyphasic approach of combining both genotypic and phenotypic characteristics to define a bacterial species could not be used for G. stearothermophilus where many phenotypic characteristics vary within this taxon. Further evidence of this discordant use of phenotypic traits was provided by analysis of the accessory genome, where the dairy strains contained a putative lac operon. Based on the findings from this study, we recommend that novel bacterial species should be defined using a core genome approach.

Investigating the Leadership Style Effect on the Technology Transfer Effectiveness: A Proposed New Model (An Applied Study on the Dairy Manufacturing Sector in Egypt)

<p><strong>Purpose: </strong>Different leadership styles' effects on technology transfer effectiveness have not been implied in the literature. This study seeks to theoretically investigate the effect of five leadership styles; Classified according to personal authority of the leader; On technology transfer effectiveness.</p><p><strong>Design/methodology/approach:</strong> This study identifies five leadership styles which affect technology transfer effectiveness including transformational leadership, transactional leadership, visionary leadership, charismatic leadership and culture based leadership. This study associates these five leadership styles to technology transfer effectiveness. A conceptual model is tested using a survey data collected from a sample of manufacturing plants in the dairy manufacturing sector in Egypt.</p><p><strong>Findings: </strong>The results indicate that only four leadership styles significantly affect technology transfer effectiveness. Visionary leadership style has the strongest significant effect on technology transfer effectiveness, followed by culture based leadership style, then charismatic leadership style then transactional leadership. Transformational leadership does not significantly affect technology transfer effectiveness.</p><p><strong>Research Limitation/Implications: </strong>Transformational leadership has been observed to have no significant effect on technology transfer effectiveness. A set of refined transformational leadership measures should be developed in future studies.</p><p><strong>Practical Implications:</strong> This paper identifies the importance of leadership styles in achieving the success of technology transfer.</p><p><strong>Originality/value: </strong>This study provides a theoretical foundation for the effect of the leadership styles on technology transfer effectiveness in the dairy manufacturing plants. This study is one of the first efforts that empirically examine the effect of leadership styles on technology transfer effectiveness.</p><p> </p>

Influence of Incubation Conditions on Biofilm Formation by Pseudomonas Fluorescens Isolated from Dairy Products and Dairy Manufacturing Plants.

In this study, biofilm formation of 64 Pseudomonas fluorescens strains isolated from milk, dairy products and dairy plants was compared. The strains were grown on Tryptic Soy Broth supplemented with 0.2% of glucose, on polystyrene microplates at 10 and 30°C for 48 h. In general, 57/64 P. fluorescens strains formed biofilm, although with great variability at both tested temperatures. Moreover, our results evidenced that the biofilm-forming ability of the strains was temperature- and strain-dependent. Interestingly, the ability of several isolates to form biofilms was associated with the low temperature after 48 h. Our findings evidenced that temperature was more important than incubation time for biofilm formation. Considering the origin of the strains, it is relevant to underline the importance of performing accurate cleaning and disinfection procedures on food processing surfaces.

The Prevalence and Control of Bacillus and Related Spore-Forming Bacteria in the Dairy Industry.

Milk produced in udder cells is sterile but due to its high nutrient content, it can be a good growth substrate for contaminating bacteria. The quality of milk is monitored via somatic cell counts and total bacterial counts, with prescribed regulatory limits to ensure quality and safety. Bacterial contaminants can cause disease, or spoilage of milk and its secondary products. Aerobic spore-forming bacteria, such as those from the genera Sporosarcina, Paenisporosarcina, Brevibacillus, Paenibacillus, Geobacillus and Bacillus, are a particular concern in this regard as they are able to survive industrial pasteurization and form biofilms within pipes and stainless steel equipment. These single or multiple-species biofilms become a reservoir of spoilage microorganisms and a cycle of contamination can be initiated. Indeed, previous studies have highlighted that these microorganisms are highly prevalent in dead ends, corners, cracks, crevices, gaskets, valves and the joints of stainless steel equipment used in the dairy manufacturing plants. Hence, adequate monitoring and control measures are essential to prevent spoilage and ensure consumer safety. Common controlling approaches include specific cleaning-in-place processes, chemical and biological biocides and other novel methods. In this review, we highlight the problems caused by these microorganisms, and discuss issues relating to their prevalence, monitoring thereof and control with respect to the dairy industry.

The Impact of Wireless Technology Feedback on Inventory Management at a Dairy Manufacturing Plant

Replacing the method of counting inventory from paper count sheets to that of wireless reliably reduced the elapsed time to complete a daily inventory of the storage cooler in a dairy manufacturing plant. The handheld computers delivered immediate prompts as well as auditory and visual feedback. Reducing the time to complete the daily inventory allowed the production planner to prepare the day's manufacturing schedule earlier in the day, thereby leading to more efficient downstream processes. The two inefficiencies noted with the original paper count sheets, such as flipping pages to locate an item in relation to its storage location and hand-entered data into the computer inventory tables, were eliminated immediately at implementation. The role of the organizational behavior management practitioner in designing work procedure changes using technical solutions, requiring a minimum of training, to accelerate key operational processes was examined.

The physico-chemical characterization of casein-modified surfaces and their influence on the adhesion of spores from a Geobacillus species

To gain a better understanding of the factors influencing spore adhesion in dairy manufacturing plants, casein-modified glass surfaces were prepared and characterized and their effect on the adhesion kinetics of spores from a Geobacillus sp., isolated from a dairy manufacturing plant (DMP) was assessed using a flow chamber. Surfaces were produced by initially silanizing glass using (3-glycidyloxypropyl) trimethoxysilane (GPS) or (3-aminopropyl) triethoxysilane to form epoxy-functionalized (G-GPS) or amino-functionalized glass (G-NH2) substrata. Casein was grafted to the G-GPS directly by its primary amino groups (G-GPS-casein) or to G-NH2 by employing glutaraldehyde as a linking agent (G-NH2-glutar-casein). The surfaces were characterised using streaming potential measurements, contact angle goniometry, infrared spectroscopy and scanning electron microscopy. The attachment rate of spores suspended in 0.1 M KCl at pH 6.8, was highest on the positively charged (+14 mV) G-NH2 surface (333 spores cm−2 s−1) compared to the negatively charged glass (−22 mV), G-GPS (−20 mV) or G-GPS-casein (−21 mV) surfaces (162, 17 or 6 spores cm−2 s−1 respectively). Whilst there was a clear decrease in attachment rate to negatively charged casein-modified surfaces compared to the positively charged amine surface, there was no clear relationship between surface hydrophobicity and spore attachment rate.

Generation of an Industry-specific Physico-chemical Allocation Matrix. Application in the Dairy Industry and Implications for Systems Analysis (9 pp)

Allocation is required when quantifying environmental impacts of individual products from multi-product manufacturing plants. The International Organization for Standardization (ISO) recommends in ISO 14041 that allocation should reflect underlying physical relationships between inputs and outputs, or in the absence of such knowledge, allocation should reflect other relationships (e.g. economic value). Economic allocation is generally recommended if process specific information on the manufacturing process is lacking. In this paper, a physico-chemical allocation matrix, based on industry-specific data from the dairy industry, is developed and discussed as an alternative allocation method. Operational data from 17 dairy manufacturing plants was used to develop an industry specific physico-chemical allocation matrix. Through an extensive process of substraction/substitution, it is possible to determine average resource use (e.g. electricity, thermal energy, water, etc) and wastewater emissions for individual dairy products within multi-product manufacturing plants. The average operational data for individual products were normalised to maintain industry confidentiality and then used as an industry specific allocation matrix. The quantity of raw milk required per product is based on the milk solids basis to account for dairy by-products that would otherwise be neglected. Applying fixed type allocation methods (e.g. economic) for all input and outputs based on the quantity of product introduces order of magnitude sized deviations from physico-chemical allocation in some cases. The error associated with the quality of the whole of factory plant data or truncation error associated with setting system boundaries is insignificant in comparison. The profound effects of the results on systems analysis are discussed. The results raise concerns about using economic allocation as a default when allocating intra-industry sectoral flows (i.e. mass and process energy) in the absence of detailed technical information. It is recommended that economic allocation is better suited as a default for reflecting inter-industry sectoral flows. The study highlights the importance of accurate causal allocation procedures that reflect industry-specific production methods. Generation of industry-specific allocation matrices is possible through a process of substitution/subtraction and optimisation. Allocation using such matrices overcomes the inherit bias of mass, process energy or price allocations for a multi-product manufacturing plant and gives a more realistic indication of resource use or emissions per product. The approach appears to be advantageous for resource use or emissions allocation if data is only available on a whole of factory basis for several plants with a similar level of technology. The industry specific allocation matrix approach will assist with allocation in multi-product LCAs where the level of technology in an industry is similar. The matrix will also benefit dairy manufacturing companies and help them more accurately allocate resources and impacts (i.e. costs) to different products within the one plant. It is recommended that similar physico-chemical allocation matrices be developed for other industry sectors with a view of ultimately coupling them with input-output analysis.

The resistance to heat of thermo-resistant streptococci attached to stainless steel in the presence of milk.

Skim milk residues had a significant impact on the sensitivity to heat of a dairy isolate of the thermo-resistant, Streptococcus thermophilus. Cells of S. thermophilus (H) suspended in water or in milk had D values at 60 degrees C of 2.0 and 14 min, respectively. Cells of S. thermophilus (H) attached to stainless steel in the presence of water or milk had D values at 60 degrees C of 2.2 and 8.1 min, respectively. The attached cells in both experiments were heat-treated in the presence of water. The increase in heat resistance could not be fully attributed to individual components (caseinate or whey) in the milk. The potential for thermo-resistant streptococci to survive heat treatment in a dairy manufacturing plant is therefore greater than may be expected for the organism in less complex environments.

The resistance to heat of thermo-resistant streptococci attached to stainless steel in the presence of milk

Skim milk residues had a significant impact on the sensitivity to heat of a dairy isolate of the thermo-resistant, Streptococcus thermophilus. Cells of S. thermophilus (H) suspended in water or in milk had D values at 60 degrees C of 2.0 and 14 min, respectively. Cells of S. thermophilus (H) attached to stainless steel in the presence of water or milk had D values at 60 degrees C of 2.2 and 8.1 min, respectively. The attached cells in both experiments were heat-treated in the presence of water. The increase in heat resistance could not be fully attributed to individual components (caseinate or whey) in the milk. The potential for thermo-resistant streptococci to survive heat treatment in a dairy manufacturing plant is therefore greater than may be expected for the organism in less complex environments.

Factors influencing attachment of thermophilic bacilli to stainless steel.

This project aimed to investigate the mechanism of attachment of the vegetative cells and spores of thermophilic bacilli to stainless steel with a view to devising strategies to limit biofilm development and survival. Spores and vegetative cells of bacterial isolates were exposed to protein denaturing agents (sodium dodecyl sulphate (SDS) and trypsin) and polysaccharide removing agents (sodium metaperiodate, trichloroacetic acid (TCA) and lysozyme). Treatment with sodium metaperiodate, TCA and lysozyme increased the number of vegetative cells attaching in many of the strains studied, while SDS and trypsin decreased attachment. Spores attached to stainless steel in greater numbers than vegetative cells, and the various treatments had less effect on this attachment than for vegetative cells. Viability of the cells or spores was not an important factor in attachment, as cells and spores rendered non-viable also attached to stainless steel in similar numbers. Coating the stainless steel with skim milk proteins decreased the attachment of both vegetative cells and spores. There was no correlation between the degree of attachment and the amount of extracellular polysaccharide (EPS) produced by each strain, surface hydrophobicity or zeta potential of vegetative cells or spores, though spores were found to be more hydrophobic than vegetative cells. The results suggest that biofilm formation by these thermophilic bacilli is probably a multifactorial process, and that cell-surface proteins play a very important role in the initial process of attachment during the formation of biofilms by these bacteria. This information will provide direction for developing improved cleaning systems to control biofilms of thermophilic bacilli in dairy manufacturing plants.