Flour Milling

Study Summary

Grain tempering water in milling is traditionally disinfected with chlorinated water to control mold and bacterial growth. However, chlorine treatment often proves inadequate — leading to contamination in tempering bins and equipment, plant shutdowns for cleaning, costly returned shipments, corrosion, and potential formation of unwanted chlorinated byproducts.

A full-scale demonstration project at Harvest States Amber Milling in Huron, Ohio, tested ozone combined with ultraviolet (UV) light as a replacement for chlorine disinfection in the tempering and handling of wheat grain.

The system used corona discharge ozone, UV-generated ozone, and UV/hydroxyl radicals in tempering water, above the augers, and in tempering bins. Over 1,000 samples were tested to compare microbial control and operational performance between chlorinated and ozonated water systems.

Key Findings

1. Microbial Control

• Average APC (aerobic plate count) with chlorine: 181,675 cfu/g

• Average APC with ozone: 42,627 cfu/g
  77% reduction in bacterial counts in finished flour.

• Later in the study, 38% of flour lots (75 of 195) had APC <10,000 cfu/g, demonstrating excellent control of bacterial contamination.

• Although mold counts weren’t quantified, visual inspections showed a similar reduction in mold buildup on equipment and lines.

2. Operational & Quality Benefits

• The ozone system effectively prevented contamination in tempering bins and equipment, which previously required shutdowns for chlorine-based cleaning.

• Reduction in microbial levels helped meet client microbial standards, minimizing the risk of product returns (which cost ~$5,000 per railcar).

• Eliminated corrosion issues and safety hazards associated with chlorine handling and storage.

• No chlorinated byproducts were introduced into the product stream.

3. Cost & ROI

• Estimated annual cost savings: $40,000/year compared to chlorine treatment.

• Operating cost: $0.18/hour (~$1,600/year).

• Capital payback: approximately 30 months.

• Additional savings likely from reduced downtime, fewer cleanings, and lower reprocessing rates.

4. System Design & Safety

• System included:

  • Corona discharge ozone for tempering water

  • UV/ozone hoods over augers to generate hydroxyl radicals

  • Gaseous ozone injection in tempering bins for surface sanitation

• Safety measures:

  • Automatic UV shutoff when hoods are opened

  • Continuous ambient ozone monitoring with auto shutdown on high levels

• System installed in parallel with existing chlorine system (backup ready).

Practical Implementation Takeaways

• Replace chlorinated tempering water with ozonated water to significantly reduce bacterial counts in finished flour.

• Integrate ozone and UV at multiple stages (water, augers, bins) for more complete microbial control.

• Expect substantial cost savings from reduced chemical handling, lower product reprocessing, and less frequent sanitation shutdowns.

• Corrosion reduction improves equipment longevity.

• A well-designed safety system allows for safe, automated operation and regulatory compliance.

Ozone and UV for Grain Milling Systems

Authors:

• Bhavnita Dhillon
• Harkanwal Sandhu
• Dennis Wiesenborn
• Frank Manthe
• Charlene Wolf-Hall

An ASABE Meeting Presentation
Paper Number: 076169

Summary:

The Electric Power Research Institute and First Energy Services have joined in a Tailored Collaboration Project to investigate the feasibility of using ozone as a substitute for chlorinated water for bacteria and mold control in a wheat processing plant. Microbiological test data of flour samples after milling show that the use of ozone results in a reduction in bacteria of approximately 75-80 percent compared with grain treated with chlorinated water. Visual inspection of equipment and lines indicates a similar reduction in mold growth. RGF Environmental Group provided the engineering design, manufacture, and installation of the ozonation equipment

Introduction:

Food safety is the most important concern confronting food processors today. This is particularly true in the grain milling industry, where incoming grain carries contamination from the field and the milling process itself creates environments conducive to the growth of mold and bacteria. Traditionally, chlorinated water is used to control bacteria and mold in grain processing. However, chlorine frequently carries its own cost concerns as well as problems in storage and the handling of chlorine gas. This project investigates the feasibility of substituting ozone for chlorine in wheat milling. Ozone has strong antimicrobial qualities and does not leave a residue, unlike chlorine. Although ozone has proven effective in disinfecting drinking water and wastewater, its effectiveness for controlling organisms in the food processing industry is only beginning to be recognized. Because of the importance of bacteria and mold control and the problems associated with chlorine, ozone is an excellent candidate for application to grain steeping and storage. The project is a Tailored Collaboration effort between EPRI and First Energy Services to introduce and evaluate the use of ozone as an antimicrobial agent in grain milling. Other participants include Harvest States Amber Milling of Huron, Ohio, which operates the facility where the test is conducted, and RGF Environmental Group of West Palm Beach, Florida, which was selected to design the ozonation system and supply the equipment.

Link:

Influence of tempering with ozonated water on the selected properties of wheat flour

Authors:

• Senol ibanoglu

Department of Food Engineering, Faculty of Engineering, The University of Gaziantep, 27310Gaziantep, Turkey
Accepted 14 October 2000

Abstract:

Soft and hard wheat samples were tempered using ozonated water ¬1.5 and 11.5 mg ozone/l). Milling ¬rate of extraction),
rheological ¬farinograph and extensograph characteristics), chemical ¬protein, falling number, sedimentation volume), colour
¬Hunter Lab values) and microbiological ¬total bacterial and yeast/moulds) properties of the parent ¯ours were evaluated.Results
indicated that tempering with ozonated water did not signi®cantly alter the chemical, physical and rheological properties of the
¯ours.A statistically signi®cant reduction in the total bacterial and yeast/mould counts were obtained after tempering with ozonated
water …P 6 0:05†.Results suggest that the water ozonated up to 11.5 mg ozone/l can be successfully used in the tempering of soft and
hard wheat without deterioration in the ¯our quality. Ó 2001 Elsevier Science Ltd.All rights reserved.

Link:

https://www.oxidationtech.com/downloads/Applications/Agri-Food-Processing/OzoneGrainMillingTemperingWheat.pdf

Study Summary

This study investigated the effects of tempering wheat with ozonated water (1.5 mg/L and 11.5 mg/L ozone concentrations) on the milling, rheological, chemical, color, and microbiological properties of the resulting flours from both soft and hard wheat varieties. The goal was to determine whether ozonated water could be used in tempering without degrading flour quality.

Key Findings

• Milling Efficiency:

  • Ozone treatment did not significantly affect extraction rates for either wheat type.

  • Indicates no structural modification in kernel components due to ozone.

• Chemical Properties:

  • Protein, ash, and moisture content were unchanged.

  • Falling number (α-amylase activity indicator) and sedimentation volume were unaffected, showing no enzymatic or protein degradation.

• Rheological Properties:

  • Farinograph & extensograph results showed no significant differences after ozonation.

  • No increase in dough strength or elasticity, implying the oxidizing effect of ozone was minimal during tempering (likely due to short contact time and ozone’s short half-life).

• Color (Hunter Lab values):

  • No significant change in lightness (L), redness (a), or yellowness (b) values.

  • Ozone concentration and contact time were insufficient to bleach or oxidize pigments in the wheat.

• Microbiological Quality:

  • Significant reduction (p ≤ 0.05) in total bacterial and yeast/mold counts with ozonated water.

  • Microbial load decreased further with higher ozone concentration (11.5 mg/L).

  • Suggests ozone’s strong antimicrobial potential compared to chlorine.

Practical Implications

1. Food Safety and Quality

• Ozonated water can be safely used for tempering both soft and hard wheat without altering flour quality.

• It provides effective microbial control, reducing contamination risks during milling and extending flour shelf life.

2. Alternative to Chlorination

• Ozone is 30,000× more effective than chlorine against some microorganisms and leaves no chemical residues.

• Ideal for sustainable and chemical-free disinfection in grain processing.

3. Operational Recommendations

• Maintain ozone concentration ≤ 11.5 mg/L for optimal microbial reduction without altering functional flour properties.

• Use in-line ozone generation systems for on-demand application since ozone decomposes rapidly.

• Monitor ozone contact time and water temperature (around 20°C) to ensure efficacy.

4. Industrial Benefits

• Enhances food safety compliance and product shelf life.

• Reduces dependence on chemical sanitizers, aligning with clean-label and eco-friendly processing trends.

Conclusion

Tempering wheat with ozonated water up to 11.5 mg/L ozone:

• Reduces microbial contamination significantly.

•  Preserves milling, chemical, and rheological quality of flour.

•  Does not cause oxidative or bleaching effects under tested conditions.

Thus, ozonated water is a practical and safe method for wheat tempering that can improve microbial safety without compromising flour performance in milling or baking.

Use of ozone as an alternative to chlorine for treatment of soft wheat flours

Authors:

• SASIVIMON CHITTRAKORN

Abstract:

Ozonation was studied as an alternative to chlorination for cake flour. Ozone treatment in a wooden tumbler at room temperature was conducted. Unchlorinated flour was treated with ozone at the rate of 0.06 L/min for 10 and 36 min using 5 lb of flour. Ozonation of cake flour
decreased pH and increased the lightness (L value) of flour. Baking studies using a high-ratio white layer cake formulation showed that the volume of cakes significantly increased (p< 0.05) as ozonation time increased and cakes were softer than those made with chlorinated or control flours. The cell brightness and number of cells measured by image analysis (C-Cell) of cakes from ozone treated flour for 36 min exhibited similar values to those from chlorinated flour. Cakes made from flours after lipid extraction and after lipid extraction plus ozonation had low volume, indicating that lipids play a role in cake performance. Identification of volatile compounds that contribute to the odor of ozone treated flour was conducted. Volatile compounds of chlorinated, unchlorinated, defatted control, and ozonated defatted flours were analyzed using a purge and trap instrument and GC-MS. Aldehydes, alcohols, hydrocarbons and other compounds were found in unchlorinated and chlorinated flours while the volatile compounds present in ozone treated flours were mainly aldehydes and ketones. A rapid reduction in volatile compounds was detected when ozone treated flours were stored uncovered in a fume hood. Ozonation of defatted soft wheat flour produced less volatile aldehydes than ozone treated whole flour.

The optimum temperature and time for ozone treatment in a metal tumbler using a response surface methodology design was studied. Time (5, 15, and 25 min) and temperature (25, 35 and 45 ºC) was used with three response parameters. The optimum ozonation time was about 8 to 11 min with the temperature range between 36 and 46 ºC. Ozone treatment for 5 to 25 min at room temperature showed an increase in unextractable polymeric protein, indicating a shift of protein to a higher molecular weight. Increase in Mixograph peak time, peak viscosity,
and water retention capacity were observed as ozonation time increased. The ozone treatment did not affect the transition temperature and enthalpy change of the flour samples.

Link:

https://www.oxidationtech.com/downloads/Applications/Agri-Food-Processing/Use%20of%20Ozone%20as%20an%20Alternative%20to%20Chlorine%20for%20Treatment%20of%20Soft%20Wheat%20Flours.pdf

Study Summary

This research explores the use of gaseous ozone treatment as an alternative to chlorine for the treatment of soft wheat flour, specifically in the context of cake-flour production (e.g., high-ratio white layer cakes). The main objectives were to:

1. Investigate the effect of ozone on the properties of soft wheat flour and its performance in cakes.

2. Analyze volatile compounds in ozone-treated flour and examine the effect of flour lipids on generated volatiles.

3. Study the effects of varying ozonation time and temperature on flour functionality and cake quality.

Key Findings

Here are the major bullet-points of what the study found:

• Ozonation decreased flour pH and increased lightness (L value) of the flour. (Abstract)

• Cakes made from ozonated flour showed significantly increased volume compared to control (p < 0.05), and were softer than those made with chlorinated or untreated flour. (Abstract)

• Image analysis of cake cell structure (C-Cell) indicated that cakes from flour treated with ozone for 36 min had cell brightness and number of cells similar to the chlorinated flour. (Abstract)

• Volatile compound analysis: In untreated and chlorinated flours various aldehydes, alcohols, hydrocarbons were found; in ozone-treated flours mainly aldehydes and ketones. (Abstract)

• Lipid extraction experiments: Cakes made from flours after lipid extraction (and after lipid extraction + ozonation) had lower volume, indicating that flour lipids play a role in cake performance under ozonation. (Abstract)

• Using response-surface methodology, optimum ozonation time was found to be ~8-11 min at a temperature range of ~36-46 °C (for a metal tumbler) for the measured responses. (Abstract)

• Ozonation (5-25 min) at room temp increased unextractable polymeric protein content, indicating a shift to higher molecular weight proteins; also increased mixograph peak time, peak viscosity, and water retention capacity as ozonation time increased. (Abstract)

• Ozone treatment did not significantly affect transition temperature or enthalpy change (thermal properties) of the flour samples. (Abstract)

• More specific results: For the flour properties and cake baking tests:

  • pH and colour of flour: Ozone increased lightness (L) and possibly reduced a* and b* values under some conditions.

  • Cake volume improved with increasing ozonation time.

  • Texture: Softer cakes from ozonated flour.

  • Volatile compounds: Ozone treatment generated a different volatile profile; some volatiles diminished quickly when stored open to air (fume hood overnight).

  • Protein: SE-HPLC showed increase in high molecular weight (HMW) polymeric proteins (unextractable polymeric protein, UPP) with ozonation time, which might correlate with enhanced cake cake-baking performance.

  • Batter properties: Specific gravity decreased and viscosity increased with ozonation time/temperature; these changes correlate with improved cake volume.

• The study concluded that ozone is a viable alternative to chlorine for soft wheat flour treatment in cake applications. (Chapter 5, Conclusions)

Practical Implications

• Ozonation of soft wheat flour can enhance cake-making performance (higher volume, softer texture) compared to untreated flour, and comparable or better than chlorinated flour.

• Because ozone decomposes rapidly and leaves no persistent chemical residues, it may be a more environmentally friendly alternative to chlorine for flour treatment.

• The modification of flour protein architecture (increased unextractable polymeric protein) suggests that ozonation may function as an oxidizing treatment improving cake flour properties (similar to what chlorine does, but with perhaps fewer side-effects).

• Volatile compound changes indicate potential sensory impacts (odor/volatile profile) that need to be managed.

• The identification of optimal time/temperature conditions provides a basis for process control when scaling up.

Implementation Suggestions

• Pilot-scale/bench-scale trials: Use a tumbler/blender apparatus to treat soft wheat flour with ozone gas at controlled flow (~0.06 L/min in the study) for the identified optimal time (approx. 8-11 min) and temperature (36-46 °C) as starting parameters.

• Control pH, colour, and mixing behaviour: Monitor pH drop, increase in L value, protein distribution (via SE-HPLC or simpler proxy) and mixing properties (mixograph peak time, viscosity) to ensure the treatment yields desired functional changes.

• Baking trials: Perform high-ratio cake baking tests (or other target product) comparing untreated, chlorinated, and ozonated flour; measure cake volume, crumb texture, cell structure (image analysis), and sensory parameters.

• Sensory/volatiles management: Check for off-odours or volatile compounds arising from ozonation (especially lipid oxidation products). If detected, consider lipid stabilization (antioxidants) or post-treatment aeration/venting (the study noted rapid reduction in volatiles if flour was stored exposed).

• Process integration: For industrial scale, integrate ozone generator and contact chamber ensuring uniform gas–flour interaction; monitor ozone concentration, flow, and off-gas destruction to comply with worker exposure limits (OSHA, etc.). The literature review in the study gives guidance for ozone generation and safety.

• Quality and regulatory compliance: Confirm that ozonation treatment does not negatively affect other flour specifications (e.g., protein content, ash, moisture, thermal properties) and that the flour still meets regulatory and functional standards for the intended baked product.

• Cost–benefit analysis: Compare capital and operating costs of ozone system versus chlorination (or other oxidants), factoring in environmental/safety benefits and improvements in product quality (e.g., higher cake volume, softer crumb).

• Shelf‐life/oxidation trade‐off: Because ozonation may increase lipid oxidation and change volatile profile, consider storing flour appropriately (cool, sealed, minimal oxygen exposure) and possibly adding antioxidant strategies if shelf life is a concern.

Ozone use in Flour Milling - Milling Operations Article

Authors:

• Dr. Jeff Gwirtz

Chlorine gas has been used for some time in the United States in treating soft wheat flours for various baking applications. High ratio cake flour, which is used in cakes containing a higher level of sugar than flour, is most often associated with chlorine gas treatment. In this application, chlorine gas has two major effects: whitening and functional improvement with respect to cake production.

The application of chlorine gas is typically two ounces per hundredweight of flour. The level is monitored and controlled by measuring the flour pH. Recently, chlorine gas has been extended to include chlorination of the wheat tempering water, thereby reducing microbial counts on the surface of the tempered grain and in the milling process itself.

MICROBIOLOGY IN FLOUR MILLING

Food-borne disease outbreaks in the United States are caused by the following (with percent of frequency): bacteria (66%), chemicals (25%), viruses (5%) and parasites (4%). Very few food-borne illnesses are the result of contaminated flour.

Bacteria are everywhere in our environment including soil, water, air, dust, edible plants and plant products, animals and animal products, the intestinal tracts of man and animals, employees’ hands and contaminated food utensils and equipment. In most cases where dangerous contamination exists in grain or grain-based products, it is usually the result of human engagement in the storage, handling or processing of the product.

Bacteria have specific nutritional and environmental needs in order to survive and reproduce. They are: food, moisture, proper atmosphere, pH, temperature and inhibitory substances. Grain and flour, of course, are a tremendous food source for material, yeast and molds. There must be adequate moisture for bacteria to grow. The amount of moisture needed is defined by the term “water activity.”

Locations in the mill with a high level of humidity or water activity (0.90 plus) will support rapid bacterial growth. However, lower relative humidity areas that remain dry and have a lower water activity (less than 0.85) will not. In older mills or in locations where cool air can move across a spout containing warm stock, condensation is known to occur and shortly thereafter the population of yeast and mold increases, forming a dark smelly mass which continues to inoculate passing stocks.

Bacillus species have been implicated in food spoilage and poisoning problems. As endospores, these mesophilic species resist a wide temperature range. Therefore, in baked products the spores germinate and damage the bread product. B. subtilis and B. lichenifomis are associated with a food spoilage known as ropey bread. Most bacteria of public health concern grow best at pH values 4.6 to 7.5. The ph of freshly milled flour is often in this range with an average of 6.1 to 6.3.

Those spoilage bacteria of public health concern grow best between 60 degrees and 120 degrees F. The growth of bacteria, yeast and mold is nothing short of phenomenal. Figure 1 (page 76) shows the growth of 216 initial cells with a doubling rate of 20 minutes.

FLOUR MICROBIOLOGICAL INDICATORS

The most common microbiological indicators in flour and  baked products are total aerobic count (often referred to as total plate count), coliform/enteric bacteria count, and yeasts and mold counts.

Total aerobic count refers to a total count of microbe colonies growing on the media plate from the sample. Coliform or enteric bacteria count is a subset of the total aerobic microbe colony count and is often used as an indicator of direct or indirect fecal contamination. Yeasts and mold counts are not included in total aerobic counts, although they are also often subject to maximum tolerances. Their main relation to food safety is the potential to produce mycotoxins, which are toxic compounds produced by fungi that contaminate plants.

It has been reported that microbial counts found in a flour mill will vary widely, depending on a number of factors such as initial counts in the grain from crop conditions, milling practices, post-milling handling, moisture content of flour and storage conditions.

Typical microbiological counts in 4

flour are 1 .5 × 10 for total aerobic count; 200 for coliforms; 120 for yeasts and 800 for molds. Significant correlations have been observed between all microbial indicators and some quality criteria (e.g. test weight) and grading factors (e.g. wheat grade number, vitreous kernel content). A weak but significant correlation has also been reported between the total plate count and the moisture content of grain.

MILLING ENVIRONMENT AND MICROBIOLOGY

Warm temperatures are required for the successful separation of bran germ and endosperm to prevent bran shattering and improve ease of endosperm reduction. Moreover, the energy input dissipates in the form of heat, driving moisture off the milled product within the process.

While temperature and relative humidity of the milling room are important, it is the temperature and humidity inside the milling processing environment where bacteria, yeast and mold may cause problems. The optimal relative humidity and temperature for milling is approximately 75 degrees F (plus or minus 10 degrees F) and 65% relative humidity (plus or minus 10%), respectively.

Figure 2 (page 78) ? presents the relative humidity inside various break sifters and on the sifter floor during a mill run in the Kansas State University Pilot Flour Mill. Notice that the room relative humidity is less than the relative humidity measured inside the sifter, which is besides the roller mill and purifier in which the wheat processing environment exists. In some locations, constantly elevated humidity and/or rapid increases in humidity cause sifting, handling and general flow problems for the miller. Temperature and relative humidity conditions outside the optimal range have significant and negative economic and technical consequences. Rapid cooling and condensation create conditions for microbial growth.

Some management practices can be employed to reduce microbial loads in the mill environment. Reducing microbial load on the wheat surface through addition of chlorine in tempering water has been reported to effectively reduce microbial load in the milling process and ultimately the flour.

In automated mills, there is a considerable temptation to simply shut down the unit when the load is taken off the milling unit. However, many automated mill programmers have extended set shutdown time periods, allowing mill shake down while pulling aspiration or suction to reduce humidity in the system where condensation onto product and processing surfaces could occur. Such practice assists in reducing surface condensation and caking, which lead to microbial development and start-up challenges. While the building and unit are warm, condensation may not be an issue. But it is best to let it cool down and dry out before shutting it down.

Another tool often used in older mills is dragging or cleaning the spouts to prevent active mold colony build-up.

OZONE PRODUCTION AND CONTROL

The following steps have been identified for the use of ozone in a primarily aqueous system and apply to milling when used in tempering water.

• Oxygen/feed gas preparation. Produce clean, dry 95% pure oxygen from the air to improve efficiency and protect the ozone generator. It requires 50% to 75% less energy to produce ozone with purified air.

• Ozone generation: Control input oxygen concentration, increase voltage and lower feed gas flow rate to optimize ozone output.

• Mass Transfer: This was generally applied to the use of ozone in the aqueous phase, which would not be applicable to use of gas on flour. Ozone transfer in PVC piping is not recommended since a portion of the ozone is lost when it reacts with the PVC pipe. Stainless  steel, such as 304 or 316, has been suggested for use in ozone transfer systems.

• Monitoring and Control: Control of oxygen concentrations, flow rates, voltage, etc., should be adequate for monitoring and control. However, any or all of these could be adjusted based on production rate, product moisture and temperature to optimize addition and provide control.

Exposure to ozone is hazardous to humans. Like chlorine gas, it attacks the respiratory tract. Standards set by the Occupational Safety and Health Administration in the United States allow a permissible exposure level of less than 0.1 milligrams per liter (mg/L) on a time-weighted average for an eight-hour work period and a maximum single exposure of 0.3 mg/L for less than a 10-minute duration. Ambient air should be tested for safety using monitors which operate on the basis of UV light absorption being a function of ozone concentration.

OZONE-CHLORINE REPLACEMENT

Ozone, zanthan gum, L–cysteine, malto-dextrins, heat, combinations of heat and ozone, chlorine and ozone blends are being studied as chlorine replacements with varying degrees of success. Ozontation was studied as an alternative to chlorination for cake flour. Flour was treated with ozone at the rate of 0.06 liters per minute for 10 and 36 minutes using 5 pounds of flour. Ozonation of cake flour decreased pH and increased the lightness (L value) of flour. Baking studies using a high-ratio white layer cake formulation showed that the volume of cakes significantly increased (p < 0.05) as ozonation time increased, and cakes were softer than those made with  chlorinated or control flours. The cell brightness and number of cells measured by image analysis (C-Cell) of cakes from ozone-treated flour for 36 minutes exhibited similar values to those from chlorinated flour.

The optimum ozonation time was about 8 to 11 minutes with the temperature range between 36 and 46 degrees C. Increase in Mixograph peak time, peak viscosity, and water retention capacity were observed as ozonation time increased. Ozonated flour was reported to have a strong odor that affected the odor and flavor in the cakes. Volatile gases dissipated when ozonated flour was stored under a fume hood, suggesting that additional research needs to be focused on how to decrease the strong odor in flours by using processing techniques or other methods.

OZONE AND UV-MICROBIAL LOAD REDUCTION

A study to investigate the feasibility of using ozone and UV light as a substitute for chlorinated tempering water for bacteria and mold control in a wheat flour mill was conducted. In the study, microbiological test data of flour samples after milling show that the use of ozone results in a reduction in bacteria of approximately 75% to 80% compared with grain treated with chlorinated water.

Visual inspection of equipment and lines indicates a similar reduction in mold growth. Data gathered during the project indicate a potential 75% to 80% reduction in total plate count bacteria in comparison to conventional treatment with chlorinated water. The average anaerobic plate count (APC) of one group of flour samples from grain treated with chlorinated water averaged 181,675 colony forming units per gram (cfu/g). In comparison, the average APC for flour from ozone-treated grain is 42,627 cfu/g, a reduction of 77%.

The last data collected on 195 samples of flour processed showed 75 lots (38%) with APC of less than 10,000 cfu per gram. Although the project did not include mold counts to quantify the effectiveness of ozone over chlorine in mold abatement, visual inspection of equipment and lines by plant staff indicates a similar reduction of mold growth in the equipment.

International use of ozone to reduce or control microbial contamination threats appears to be growing rapidly in all food sectors. Grain-based products, because of their low moisture and water activity and the non-deleterious nature of their general microbial contaminants, make this product group one of the last to be treated with ozone for microbial control. Use of ozone to replace chlorine gas driven by both safety and residue concerns continues to be aggressively pursued.

Link to Original Article