Efficacy of home washing methods in controlling surface microbial contamination on fresh produce

Much effort has been focused on sanitation of fresh produce at the commercial level; however, few options are available to the consumer. The purpose of this study was to determine the efficacy of different cleaning methods in reducing bacterial contamination on fresh produce in a home setting. Lettuce, broccoli, apples, and tomatoes were inoculated with Listeria innocua and then subjected to combinations of the following cleaning procedures: (i) soak for 2 min in tap water, Veggie Wash solution, 5% vinegar solution, or 13% lemon solution and (ii) rinse under running tap water, rinse and rub under running tap water, brush under running tap water, or wipe with wet/dry paper towel. Presoaking in water before rinsing significantly reduced bacteria in apples, tomatoes, and lettuce, but not in broccoli. Wiping apples and tomatoes with wet or dry paper towel showed lower bacterial reductions compared with soaking and rinsing procedures. Blossom ends of apples were more contaminated than the surface after soaking and rinsing; similar results were observed between flower section and stem of broccoli. Reductions of L. innocua in both tomatoes and apples (2.01 to 2.89 log CFU/g) were more than in lettuce and broccoli (1.41 to 1.88 log CFU/g) when subjected to same washing procedures. Reductions of surface contamination of lettuce after soaking in lemon or vinegar solutions were not significantly different (P > 0.05) from lettuce soaking in cold tap water. Therefore, educators and extension workers might consider it appropriate to instruct consumers to rub or brush fresh produce under cold running tap water before consumption.     

Removal of Microbial Biofilms from Dispense Equipment: The Effect of Enzymatic Pre‐digestion and Detergent Treatment

Microbial biofilms can form in dispense outlets as a result of poor or inadequate cleaning and can be difficult to remove using conventional practices. Enzymatic cleaners might help to remove biofilms by degrading the exopolysaccharide layers in which the microbes are embedded. A multispecies biofilm comprising wild type dispense isolates of Flavimonas oryzihabitans, Lactobacillus brevis, Leuconostoc mesenteroides and Saccharomyces cerevisiae was generated on a section of tubing and fitted into a pilot dispense system, which was left uncleaned for 12 weeks. After cleaning approximately 10⁴ viable aerobes and 10³ viable anaerobes were still present. Stainless steel coupons and pieces of dispense line contaminated with biofilm were incubated in the laboratory with an enzyme mix containing varying proportions of α‐amylase, β‐glucuronidase, glucose oxidase, dextranase, protease and pectinase. Cultures grown on stainless steel had significantly (F pr. > 0.05) less viable cells than non‐enzyme treated biofilms, but this was dependent on the microbial species. Typically Lactobacillus brevis was most susceptible to the enzyme treatment. Cultures grown on dispense line were much more resistant to enzymatic digestion. Pre‐digestion with protease was most effective for removal of Lactobacillus brevis and Leuconostoc mesenteroides but not for Saccharomyces cerevisiae and Flavimonas oryzihabitans. In the simulated bar, pre‐digestion with protease reduced the viable cell count by 0.64 log units for the aerobes and 1.9 log units for the anaerobes. This study demonstrates that pre‐digestion with enzyme solutions before line cleaning is useful for treating heavily contaminated lines in trade.     

Craft Beer Microflora Identification Before and After a Cleaning Process

Although beer is a relatively safe product, growth of spoilage microorganisms can cause economic damage. The most effective way to prevent the spoilage of beer is to control contamination with adequate cleaning and sanitation. The aim of this work was to evaluate the microbial flora present both before and after a specific hygiene process was implemented during a brewpub's craft beer production. Various selective and differential culture media methods for the enumeration of beer‐spoilage species are available, but they are time consuming compared to modern techniques. The utilisation of accurate molecular methods, added to the routine microbiological analyses, allowed for the fast identification of common environmental contaminants of beer. A poor sanitation plan by the brewer resulted in microbial contamination of the brewpub. This result demonstrates the importance of good sanitation to avoid the presence of undesirable microorganisms in the product. A cleaning‐in‐place (CIP) method, in operation in many small breweries, could be utilised to prevent the occurrence of such brewery and beer microbial contaminants. In small breweries, the simplest CIP units consist of a single tank and a portable pump. This method requires no additional equipment besides a spraying ball, which is usually included in the design of most tanks.     

Efficacy of Slightly Acidic Electrolyzed Water and UV‐Ozonated Water Combination for Inactivating Escherichia Coli O157:H7 on Romaine and Iceberg Lettuce during Spray Washing Process

Spray washing is a common sanitizing method for the fresh produce industry. The purpose of this research was to investigate the antimicrobial effect of spraying slightly acidic electrolyzed water (SAEW) and a combination of ozonated water with ultraviolet (UV) in reducing Escherichia coli O157:H7 on romaine and iceberg lettuces. Both romaine and iceberg lettuces were spot inoculated with 100 μL of a 3 strain mixture of E. coli O157:H7 to achieve an inoculum of 6 log CFU/g on lettuce. A strong antimicrobial effect was observed for the UV‐ozonated water combination, which reduced the population of E. coli by 5 log CFU/g of E. coli O157:H7 on both lettuces. SAEW achieved about 5 log CFU/g reductions in the bacterial counts on romaine lettuce. However, less than 2.5 log CFU/g in the population of E. coli O157:H7 was reduced on iceberg lettuce. The difference may be due to bacteria aggregation near and within stomata for iceberg lettuce but not for romaine lettuce. The UV light treatment may stimulate the opening of the stomata for the UV‐ozonated water treatment and hence achieve better bacterial inactivation than the SAEW treatment for iceberg lettuce. Our results demonstrated that the combined treatment of SAEW and UV‐ozonated water in the spray washing process could more effectively reduce E. coli O157:H7 on lettuce, which in turn may help reduce incidences of E. coli O157:H7 outbreaks.     

Effect of washing treatments on pesticide residues and antioxidant compounds in Yuja (Citrus junos Sieb ex Tanaka)

This study investigated the removal efficiency of pesticide residues and microorganisms, and changes of the amount of antioxidant compounds on yuja (Citrus junos Sieb ex Tanaka) by various washing methods. The washing methods were mechanical washing (MW), mechanical washing after soaking in SAcEW, strong acidic electrolyzed water (SAcEW+MW), and soaking detergent solution (DW), with a tap water washing (TW) as the control. After treatment of MW and SAcEW+MW, the microbial count were 3.71 and 2.66 log CFU/g, respectively. Compared with the TW treatment (5.77 log CFU /g), MW and SAcEW+MW treatments showed a higher reduction. As a result of pesticide residue, the SAcEW+MW removed 70.5–98.1% and was the most effective, regardless of the pesticides. Antioxdant activities, as measured by DPPH radical, ranged from 20.36 to 21.27% and there was no significant difference from the washing methods. The results of this study demonstrated that the SAcEW+MW was the most effective method for removing residual pesticides without affecting the quality of the yuja.     

Draught beer hygiene: a forcing test to assess quality

The quality of draught beer is important to consumers but can be inconsistent, ranging from excellent through to unacceptable. The few, dated studies of draught beer quality have focused on the number of microorganisms that are present in the product. Work reported here suggests that this approach has its limitations and fails to relate to beer quality post‐dispense. An alternative approach using the long‐established ‘forcing’ method provides a better but still retrospective assessment of draught beer quality. Samples post dispense are ‘forced’ by static incubation at 30°C for four days and beer quality is ranked by the measurement of absorbance at 660 nm. The increase in absorbance reflects the growth of beer spoilage microorganisms present in the beer at dispense. Four quality bands are proposed, where quality is described as excellent (absorbance increase of <0.3), acceptable (0.3–0.6), poor (0.6–0.9) and unacceptable (>0.9). The method is straightforward, requires no special skills and enables, for the first time, the robust quantification of draught beer quality. It is anticipated that the method will have widespread application in the measurement and improvement of the quality of draught beer. Copyright © 2017 The Institute of Brewing & Distilling     

Decontamination of lettuce using acidic electrolyzed water

The disinfectant effect of acidic electrolyzed water (AcEW), ozonated water, and sodium hypochlorite (NaOCl) solution on lettuce was examined. AcEW (pH 2.6; oxidation reduction potential, 1140 mV; 30 ppm of available chlorine) and NaOCl solution (150 ppm of available chlorine) reduced viable aerobes in lettuce by 2 log CFU/g within 10 min. For lettuce washed in alkaline electrolyzed water (AIEW) for 1 min and then disinfected in AcEW for 1 min, viable aerobes were reduced by 2 log CFU/g. On the other hand, ozonated water containing 5 ppm of ozone reduced viable aerobes in lettuce 1.5 log CFU/g within 10 min. It was discovered that AcEW showed a higher disinfectant effect than did ozonated water significantly at P < 0.05. It was confirmed by swabbing test that AcEW, ozonated water, and NaOCI solution removed aerobic bacteria, coliform bacteria, molds, and yeasts on the surface of lettuce. Therefore, residual microorganisms after the decontamination of lettuce were either in the inside of the cellular tissue, such as the stomata, or making biofilm on the surface of lettuce. Biofilms were observed by a scanning electron microscope on the surface of the lettuce treated with AcEW. Moreover, it was shown that the spores of bacteria on the surface were not removed by any treatment in this study. However, it was also observed that the surface structure of lettuce was not damaged by any treatment in this study. Thus, the use of AcEW for decontamination of fresh lettuce was suggested to be an effective means of controlling microorganisms.     

超声联合过氧乙酸清洗对生姜品质的影响

目的 考查浸泡、振荡、超声单独或协同方式及其联合过氧乙酸(peroxide acetic acid, PAA)清洗对生姜表面泥沙、微生物去除效果及对贮藏品质的影响。方法 比较水清洗、PAA溶液清洗、超声清洗及其组合的12种清洗方式对生姜表面泥沙、霉菌和酵母菌、电解质泄漏率、呼吸强度、失重率、总酚含量、总黄酮含量、抗氧化性等比较分析得出最佳的清洗方式。结果 与水振荡清洗相比, PAA显著提高了泥沙清洁率(5.31%降低至4.50%) , 且与超声清洗协同可显著增加清洁率(4.50%降低至1.85%), 清洗前浸泡显著提高泥沙清洁率(约0.7%)。PAA清洗降低生姜表面微生物约0.8 log CFU/g, 而联合超声后可降低2.2 log CFU/g。超声促进了电解质泄漏, 超声处理时间越长, 电解质泄漏率越高。储藏期间清洗的生姜失重率显著增加, 超声清洗30 min后生姜储藏期间呼吸强度显著升高。与水振荡清洗相比, PAA溶液对生姜总多酚、总黄酮含量没有显著影响, 但超声波清洗30 min总酚含量显著下降, 抗氧化活性变化趋势与之一致。结论 使用PAA溶液, 先浸泡, 然后超声, 最后振荡(各10 min)的联合清洗方式是生姜最佳的清洗方式。     

Cleaning in place with onsite‐generated electrolysed oxidizing water for water‐saving disinfection in breweries

The use of acid electrolysed water (AcEW) is a relatively new sanitizing technique for brewery equipment. Experiments showed that a 30% AcEW (a free chlorine concentration of above 17 mg/L) was a sufficient and effective alternative to conventional sanitizers such as peracetic acid (2%). On the basis of the results of industrial‐scale clean‐in‐place tests, an effective AcEW‐based clean‐in‐place procedure, which requires only 10 min of cleaning and does not require final water rinsing after sanitation, was established for the bright beer tank. Copyright © 2013 The Institute of Brewing & Distilling     

Efficacy of acidic electrolyzed water for microbial decontamination of cucumbers and strawberries

An examination was made of the efficacy of acidic electrolyzed water (AcEW, 30 ppm free available chlorine), ozonated water (5 ppm ozone), and a sodium hypochlorite solution (NaOCl, 150 ppm free available chlorine) for use as potential sanitizers of cucumbers and strawberries. AcEW and NaOCl reduced the aerobic mesophiles naturally present on cucumbers within 10 min by 1.4 and 1.2 log CFU per cucumber, respectively. The reduction by ozonated water (0.7 log CFU per cucumber) was significantly less than that of AcEW or NaOCl (P < or = 0.05). Cucumbers washed in alkaline electrolyzed water for 5 min and then treated with AcEW for 5 min showed a reduction in aerobic mesophiles that was at least 2 log CFU per cucumber greater than that of other treatments (P < or = 0.05). This treatment was also effective in reducing levels of coliform bacteria and fungi associated with cucumbers. All treatments offered greater microbial reduction on the cucumber surface than in the cucumber homogenate. Aerobic mesophiles associated with strawberries were reduced by less than 1 log CFU per strawberry after each treatment. Coliform bacteria and fungi associated with strawberries were reduced by 1.0 to 1.5 log CFU per strawberry after each treatment. Microbial reduction was approximately 0.5 log CFU per strawberry greater on the strawberry surface than in the strawberry homogenate. However, neither treatment was able to completely inactivate or remove the microorganisms from the surface of the cucumber or strawberry.     

Evaluation of efficacy of four commercial enzyme-based cleaners of ultrafiltration systems

Use of UF and RO in the dairy industry is rapidly expanding. Because the dairy industry demands high levels of cleanliness, this new technology requires close evaluation to assure adherence to these standards. Efficacy of four commercial enzyme-based cleaners (pH 7.0 to 8.4) in UF systems was determined by microbiological evaluation and permeate flux restoration. The UF system containing two polysulfone UF membranes in parallel, was soiled by recycling 380 L of sweet whey (40 degrees C) for 2.0 h followed by concentrating whey for .5 h. The cleaning cycle consisted of acid cleaner (.5 h, 40 degrees C), followed by enzyme cleaner (10.0 h, 40 degrees C), and rinsing (2.0 h, 40 degrees C). A chlorine sanitizer was circulated (5 min, 40 degrees C) and the unit containing sanitizing solution left idle overnight. Flux was determined and swabs and rinse water samples were taken immediately after soiling, after cleaning, and the next morning to check sanitizing. The four enzyme-based cleaners were unsatisfactory when microbiological criteria were considered. Loss of sanitizer strength and problems with yeast and especially mold growth over time also indicated lack of effective cleaning. Flux, however, was restored easily and did not correlate with efficacy of cleaning based on numbers of microorganisms remaining.     

Effect of alfalfa seed washing on the organic carbon concentration in chlorinated and ozonated water

The bioassays assimilable organic carbon (AOC) and coliform growth response are better indexes than biological oxygen demand to determine water quality and water's ability to support the growth of bacteria. Ozonated (5 mg/liter) and chlorinated tap water were used to wash alfalfa seeds for 30 min. After washing in the ozonated tap water, the AOC concentration increased 25-fold, whereas the dissolved ozone decreased to undetectable levels. The AOC levels for the chlorinated water after washing the seeds also increased. These increases are due to ozone's strong oxidizing ability to break down refractory, large-molecular-weight compounds, forming smaller ones, which are readily used as nutrient sources for microorganisms. This same phenomenon was observed when using ozone in the treatment of drinking water. The AOC value increased from 1,176 to 1,758 micrograms C-eq/liter after the reconditioned wastewater was ozonated. When the ozonated wastewater was inoculated with Salmonella serotypes, the cells survived and increased generation times were observed. The increased nutrients would now become more readily available to any pathogenic microorganisms located on alfalfa seed surface as seen with the increase in the inoculated levels of Salmonella in the ozonated wastewater. If the washing process using ozonated water is not followed by the recommended hypochlorite treatment or continually purged with ozone, pathogen growth is still possible.     

6种清洗方法对果蔬中2种甲氧基丙烯酸酯类农药残留的去除效果

分别采用清水、果蔬洗涤盐溶液、奶粉溶液、比亚酶蔬菜速洗液、洗洁精浸泡和洗菜机清洗6种方法清洗吡唑嘧菌酯和嘧菌酯污染的黄瓜及草莓,QuEChERS-LC-MS/MS法处理并检测黄瓜和草莓中吡唑醚菌酯及嘧菌酯的残留量。结果表明:奶粉对黄瓜和草莓上2种农药残留的整体清除效果最好,清除率为60.01%~69.91%,显著(p<0.05)高于洗洁精和清水浸泡。洗菜机对草莓上农药残留的清除率为59.55%~64.87%,高于对黄瓜上农药残留的清除率40.29%~48.40%。果蔬洗涤盐和比亚酶的农残清除效果无明显差异,清除率分别为39.91%~64.50%和39.63%~65.35%。洗洁精农残清除率为32.50%~52.02%。清水清除率最低,为22.45%~44.41%,显著低于奶粉、洗涤盐和比亚酶浸泡效果(p<0.05)。综上所述,不同清洗方法均可减少果蔬中的农药残留,其中奶粉溶液浸泡处理效果最好,清水最差。     

Effective cleaning and sanitizing of polysulfone ultrafiltration membrane systems.

Polysulfone UF membranes that were soiled by Cheddar cheese whey were successfully cleaned in place. This cleaning procedure was completed in about 1 h. Most cleaning chemicals used were common and inexpensive. The cleaning procedure consisted of rinsing the membrane system for 2 min with water initially and after each cleaning solution. Sodium hydroxide at pH 11.0, with .1% of a nonionic surfactant added, was circulated for 20 min. After a 2-min rinse with water, a 1:1 mixture of nitric and phosphoric acids at pH 2 was circulated for 20 min and rinsed again with water. Finally, sodium hydroxide at pH 11.0, with 200 ppm of sodium hypochlorite added, was circulated for 20 min and rinsed. All cleaning solutions and all rinse waters were at 54 degrees C. Membranes cleaned by this procedure were found to be free from whey residue under examination by scanning electron microscopy. The cleaning process did not damage the membranes even when it was used continuously for 300 h. Microbial populations on the membrane were estimated by incubating small (4-cm2) sections of membrane in screw-cap vials filled with trypticase soy broth. From the portion of vials showing growth after 72 h at 32 degrees C, a most probable microbial population was calculated. Santizing cleaned polysulfone UF membranes with 100 ppm of sodium hypochlorite or 100 ppm of dichloroisocyanurate at 54 degrees C resulted in membranes free from viable microorganisms. When dichloroisocyanurate was used at 10 degrees C and 200 ppm, a most probable microbial population of 290/m2 was found. No microbial growth was detected when cleaned and sanitized membranes were stored in tap water for 24 h. This technique for cleaning UF membranes does not require the use of a holding solution containing santizers to control the growth of residual microorganisms.     

Efficacy of ozone in killing Listeria monocytogenes on alfalfa seeds and sprouts and effects on sensory quality of sprouts

A study was done to determine the efficacy of aqueous ozone treatment in killing Listeria monocytogenes on inoculated alfalfa seeds and sprouts. Reductions in populations of naturally occurring aerobic microorganisms on sprouts and changes in the sensory quality of sprouts were also determined. The treatment (10 or 20 min) of seeds in water (4 degrees C) containing an initial concentration of 21.8 +/- 0.1 microg/ml of ozone failed to cause a significant (P < or = 0.05) reduction in populations of L. monocytogenes. The continuous sparging of seeds with ozonated water (initial ozone concentration of 21.3 +/- 0.2 microg/ml) for 20 min significantly reduced the population by 1.48 log10 CFU/g. The treatment (2 min) of inoculated alfalfa sprouts with water containing 5.0 +/- 0.5, 9.0 +/- 0.5, or 23.2 +/- 1.6 microg/ml of ozone resulted in significant (P < or = 0.05) reductions of 0.78, 0.81, and 0.91 log10 CFU/g, respectively, compared to populations detected on sprouts treated with water. Treatments (2 min) with up to 23.3 +/- 1.6 microg/ml of ozone did not significantly (P > 0.05) reduce populations of aerobic naturally occurring microorganisms. The continuous sparging of sprouts with ozonated water for 5 to 20 min caused significant reductions in L. monocytogenes and natural microbiota compared to soaking in water (control) but did not enhance the lethality compared to the sprouts not treated with continuous sparging. The treatment of sprouts with ozonated water (20.0 microg/ml) for 5 or 10 min caused a significant deterioration in the sensory quality during subsequent storage at 4 degrees C for 7 to 11 days. Scanning electron microscopy of uninoculated alfalfa seeds and sprouts showed physical damage, fungal and bacterial growth, and biofilm formation that provide evidence of factors contributing to the difficulty of killing microorganisms by treatment with ozone and other sanitizers.     

不同条件对糙米发芽过程中微生物数量的影响

为了确定安全食用的发芽糙米生产方法,在不同温度和不同的发芽方法下,对不清洗和定时清洗的糙米进行微生物检测.结果表明,采用浸泡发芽法和密闭气相发芽法时,温度越高.发芽时间越长,细菌总数越多,定时清洗只能适当减少微生物的数量,如密闭气相发芽法,25℃、48h,不定时清洗的样品细菌总数达到2.43×10~8cfu/g,定时清洗的样品细菌总数为1.31 × 10~8cfu/g.而流动水相发芽法的样品细菌总数仅为6.5 × 10~3cfu/g,远低于其他两种发芽方法.因此,相对于传统发芽法,流动水相法是较为安全的发芽方法.     

Reducing Salmonella on cantaloupes and honeydew melons using wash practices applicable to postharvest handling, foodservice, and consumer preparation

Washing conditions that included a soak or brush scrub were evaluated for removal of Salmonella from the surface of smooth (honeydew) or complex (cantaloupe) melon rinds. Melon rinds were spot-inoculated onto a 2.5 cm2 area of rind (squares) with approximately 6.0 log(10) CFU/square of an avirulent nalidixic acid-resistant strain of Salmonella typhimurium. Melons were washed by immersion in 1500 ml of water or 200 ppm total chlorine and allowed to soak or were scrubbed over the entire melon surface with a sterile vegetable brush for 60 s. Inoculated sites, uninoculated sites ("next to" sites) that were adjacent to inoculated sites, and sites on the side of the melon opposite (remote sites) the inoculated site were excised and pummeled in a stomacher for 2 min prior to plating onto tryptic soy or bismuth sulfite agar supplemented with 50 microg/ml nalidixic acid. S. typhimurium was reduced on the rind of cantaloupe by 1.8 log CFU/melon after soaking for 60 s in 200 ppm total chlorine, which was significantly better than the 0.7 log CFU/melon achieved with soaking in water. For both water and 200 ppm total chlorine, scrubbing with a vegetable brush was shown to be significantly (0.9 log CFU/cantaloupe) more effective than soaking alone. When honeydew melons were soaked or scrubbed in water, reductions of 2.8 log CFU/melon or >4.6 log CFU/melon (four of five samples), respectively, were observed. However, when water treatments were used, the presence of Salmonella-positive "next to" and remote sites indicated that bacteria were spread from inoculated site on the rind to uninoculated sites either through the rinse water (40-70 CFU/ml of Salmonella) or scrub brush (400-500 CFU/brush). Transfer to other sites occurred more often with cantaloupe than honeydew melons. This transfer was eliminated when 200 ppm total chlorine was used. When 200 ppm total chlorine was used, Salmonella could not be detected in the water or on the scrub brush. For optimal microbial removal in food service and home settings, melons should be scrubbed with a clean brush under running water. However, to ensure the benefits of brushing, instructions for cleaning and sanitizing brushes must also be emphasized. For food service settings where concentration and pH can be adequately measured, the use of chlorinated water may provide additional benefit.     

Evaluation of various antimicrobial interventions for the reduction of Escherichia coli O157:H7 on bovine heads during processing

The effectiveness of electrolyzed oxidizing water, FreshFx, hot water, DL-lactic acid, and ozonated water was determined using a model carcass spray-washing cabinet. A total of 140 beef heads obtained from a commercial processing line were inoculated with Escherichia coli O157:H7 on the cheek areas. Each head was exposed to a simulated preevisceration wash and then had antimicrobial wash treatments. Hot water, lactic acid, and FreshFx treatments reduced E. coli O157:H7 on inoculated beef heads by 1.72, 1.52, and 1.06 log CFU/cm2, respectively, relative to the simulated preevisceration wash. Electrolyzed oxidizing water and ozonated water reduced E. coli O157:H7 less than 0.50 log CFU/cm2. Hot water, lactic acid, and FreshFx could be used as decontamination washes for the reduction of E. coli O157:H7 on bovine head and cheek meat.     

Development and Evaluation of an Ozonated Water System for Antimicrobial Treatment of Durum Wheat

ABSTRACT:  Ozonated water is reported to be effective in reducing the microbial load in foods such as fruits, vegetables, and grains. Ozonated water may be an effective alternative to chlorinated water in treating durum wheat before milling. Therefore, durum wheat was washed with ozonated water and analyzed for yeast and mold count (YMC) and aerobic plate count (APC). A system for producing and monitoring ozonated water was developed. The effect of water quality (tap, distilled, and ultra-pure), temperature (7, 15, and 25 °C), and pH (2, 4, and 6.5) was evaluated on the following: steady-state dissolved ozone concentration, ozone decay constant, half-life, mass transfer coefficient, equilibrium ozone concentration, and solubility ratio. The study of these parameters was important to attain a stable, high dissolved ozone concentration at the outset of washing and to have information for system improvement and scale-up. A 1% acetic acid solution (pH 2) at 15 °C resulted in high dissolved ozone concentration (21.8 mg/L) and long half-life (9.2 min). Subsequently, wheat was washed with 5 wash water types: distilled water, ozonated water (16.5 mg/L), chlorinated water (700 mg/L), acetic acid solution (1%), and acetic acid + ozonated water (1%, 20.5 mg/L). The treated samples were analyzed for YMC and APC. The acetic acid + ozonated water treatment was the most effective, with a reduction of 4.1 and 3.2 log₁₀ colony forming units/g in YMC and APC, respectively. Though ozonated water was not very effective alone, it was useful in combination with acetic acid.     

High‐pressure homogenization: a non‐thermal process applied for inactivation of spoilage microorganisms in beer

The inactivation of spoilage microorganisms in beer using high‐pressure homogenization (HPH) was studied with the aim of evaluating the possibility of changing the conventional pasteurization process using this particular process. The homogenization pressure required for the inactivation of lactic acid bacteria, acetic bacteria and yeasts was investigated. For the most resistant microorganisms, the pressure inactivation kinetics and the effects of multiple process passes, initial temperature of the beer and the CO₂ concentration were studied. The results indicated that Lactobacillus delbrueckii was the most resistant microorganism tested, requiring 250 MPa to reach a six decimal reduction. Additionally, results showed that L. delbrueckii inactivation followed a second‐order kinetic process. A multi‐pass process and the use of a high initial beer temperature increased inactivation by HPH with L. delbrueckii, allowing the use of 150 MPa to achieve a five log cycle of inactivation. In contrast, a high CO₂ concentration reduced the efficacy of the HPH process. The results that were obtained are useful for high‐pressure homogenization applications in breweries and help to elucidate the effect of this new technology in a beverage that is both alcoholic and carbonated. Copyright © 2013 The Institute of Brewing & Distilling