C-29

Utilization of spray wash with organic acids (peroxyacetic acid and lactic acid) and 

chlorinated wash in combination, utilizing direct application methods, for pathogen 

reduction on pork and beef carcasses in small and very small meat processing 

plants (revised 8/24/2005) 

University of Georgia Food Science Extension Outreach Program, Athens, Georgia 

A. Estes Reynolds, Jr., PhD 

Introduction: 

The efficacy of organic acids to reduce total bacterial loads and pathogens has been well 

demonstrated over the past 30 years (Reynolds, 1973; Dickson and Anderson, 1992; Handin et al., 

1995). Numerous methods of applying antimicrobial solutions to beef and pork carcasses have 

been developed, but most are too expensive for use in small and very small meat processing 

plants. 

This study was designed to evaluate the effectiveness of acid spray wash with peroxyacetic acid 

(180-200 ppm) or lactic acid (2% to 2.5%) on beef and pork carcasses using a hand sprayer with 

fan jet nozzle at 20-30 psi. The number of carcasses tested varied with each of the three trials due 

to the availability of animals. One phase tested hot pork carcasses destined for immediate 

processing prior to chilling. There is no previous research information on decontaminating hot pork 

carcasses utilized immediately to produce fresh pork sausage. 

Objective: 

To develop methods of application of organic acids and other antimicrobial agents for use in small 

and every small processing plants that will effectively contribute to the reduction of pathogens on 

pork and beef carcasses. Special attention will be given to application to hot hog carcasses to be 

utilized prior to chilling. 

Materials & Methods 

Spray equipment 

2-4 gallon, hand-pump sprayers with fan nozzle, cost less than $100 each. 

Chemicals used 

Lactic acid (88% Food Grade, Fisher Scientific); peroxyacetic acid (180-200 ppm, Inspexx 100, 

Ecolab). Strength of the wash solutions were tested with a dissolved solids test meter. 

Lactic acid 2% solution was formulated by mixing five ounces of lactic acid into two gallons of 

water. The peroxyacetic acid solution was mixed by adding 20 ml to 5 gallons of water. 

Pork carcasses 

Hot pork carcasses were swab tested for total aerobic plate count, E.coli, Salmonella, and coliform 

contamination. Hot carcasses from market hogs were sprayed subsequent to the final chlorine 

(50ppm) wash. These carcasses were to be immediately processed into fresh pork sausage. 

Beef carcasses 

Beef carcasses were first swabbed hot before spraying for total aerobic plate count, E. coli, 

Salmonella and coliform contamination. Carcasses were sprayed and chilled, then swabbed for 

total aerobic plate count, E. coli, Salmonella and coliform contamination. 
!

Treatments 

Pork carcass spray washing: 

Hot pork carcasses from market hogs were sprayed subsequent to the final chlorine wash (50ppm). 

The carcasses were sprayed using hand pump sprayers with a jet fan nozzle at 20-30 psi, using 

2% lactic acid or 180-200 ppm peroxyacetic acid. The number of carcasses varied in each of the 

three trials due to the availability of animals. Carcasses were sampled on one side prior to spraying 

as a control. Carcasses were acid sprayed and allowed to drain for five minutes prior to sampling 

the opposite side. Sampling procedures were in accordance with USDA E. coli sampling. 

Beef carcass spray washing: 

Hot beef carcasses were washed and rinsed with a 40 ppm chlorine solution. After washing, the hot 

carcasses were sampled in accordance with USDA sampling procedures for E. coli. This served as 

the control. 

The carcasses were then sprayed with 2.0% to 2.5% solution of lactic acid or 180-200 ppm 

peroxyacetic acid. The spraying was accomplished using hand pump sprayers with a jet fan nozzle 

at 20-30 psi. 

One group of beef carcasses was treated with a hot water (180 F) wash, but this step was 

discontinued after the first trial because it did not reduce Salmonella positives. 

Results 

Pork: 

The peroxyacetic wash showed a .3 to 1.0 log 10 reduction in aerobic plate counts, and had a 50% 

reduction in the number of positive Salmonella samples. E. coli and coliform counts were lower 

than on the untreated control samples. 

Lactic acid wash (2%) gave a 0 to 1.2 log 10 reduction in aerobic plate counts and a 66% reduction 

in the number of positive Salmonella samples. Both acids were effective in reducing the total 

aerobic plate count, E. coli and coliform counts to less than 10 CFU/ml and were effective in killing 

enteric organisms. Lactic acid was easier to handle, did not require refrigerated storage and had a 

residual effect on the microbial load, on especially enteric organisms, as shown by the data. 

Beef: 

Peroxyacetic acid was effective in reducing the aerobic plate count in two of the three trials by 1 

log10. One trial was chilled using a chlorine spray during chilling and the aerobic plate count 

increased by 1.1 log10 CFU/ml. No positive Salmonella samples were found in any of the 

peroxyacetic acid treated carcasses in any trial. E. coli were for the most part below 10 CFU/ml for 

all samples. 

Lactic acid treated carcasses showed a 0.5 to 0.7 log 10 reduction in aerobic plate counts, but a 

1.8 log 10 increase in the spray chill carcasses. No positive Salmonella samples were found in any 

of the treated samples and E. coli was maintained below 10 CFU/ml in the sampled carcasses. 

A post-chill peroxyacetic acid wash was used on the carcasses after chilling in Trial # 1 and 

resulted in two positives for Salmonella, probably due to the extra handling of the carcasses. 

Recommendations for use: 

A 2.0% lactic acid solution is recommended for hot pork carcasses that are to be used immediately 

in the production of pork sausage. One gallon of solution should cover 10 hog carcasses 

effectively. 
Use either 2.0% to 2.5% solution of lactic acid or 180-200 ppm peroxyacetic acid in conjunction 

with a 40-50 ppm chlorine wash on beef carcasses. Two gallons of solution should cover 20 beef 

carcasses effectively. 

A 2-4 gallon, hand-pump sprayer with a jet fan nozzle at 20-30 psi at a cost less than $100. 

Lactic acid can be purchased in bulk from most commercial chemical distributors or in a smaller 

quantity from Fisher Scientific. Peroxyacetic acid is also available from chemical distributors; one 

brand, Inspexx 100, can be purchased from Ecolab. 

Proper handling and storage of the chemicals is very important. Peroxyacetic acid requires 

refrigerated storage; MSDS sheets from the supplier should be placed with the HACCP plan; 

copies also should be displayed in the chemical storage area for quick reference. 

Strength of the wash solutions should be tested with a dissolved solids test meter. 

Benefits to Small/Very Small Plants 

For beef, peroxyacetic acid was more effective, but lactic acid has additional residual effect. For 

pork, lactic acid spray wash was most effective in reducing the TPC, Salmonella and E. coli 

positives when preceded by a chlorine (40-50ppm) final wash prior to chilling. Thus, maintaining 

effective free chlorine levels in the final wash water is very important. 

Approximate Costs for Organic Acid Spray in Beef/Pork Processing Plants 

Cost per 

List Price Gal. of Cost per 

Organic Acid (50 gal) Cost per Unit Solution Carcass* 

Lactic Acid (88% food grade) $ 800.00 $ 0.1250 (oz) $ 0.64 $ 0.064 (hog) 

2% solution = 5 oz + 2 gal H2O $0.128 (beef) 

Peroxyacetic Acid $ 1,336.10 $ 0.0071 (mL) $ 0.0282 $ 0.00282 (hog) 

200 ppm = 8 mL + 2 gal H2O $ 0.00565 (beef) 

* One gallon of 2% lactic acid or peroxyacetic acid (180-200 ppm) will treat approximately 10 

hogs or 5 beef carcasses. 

Revised summary emailed to Howard Early 8-3-05 ebm 

Table revised 8-24-05 ebm 

Entire report with procedure steps emailed to Howard Early & Dr. Murthy 8-26-05 
ADDED 8-24-05 per request of Dr. Murthy 

Utilization of spray wash with organic acids (peroxyacetic acid and lactic acid) and 

chlorinated wash in combination, utilizing direct application methods, for pathogen 

reduction on pork and beef carcasses in small and very small meat processing 

plants (revised 8/24/2005) 

Steps in applying acids using spray method to reduce pathogens 

Step 1 

A. Purchase a two to four-gallon stainless steel or plastic pump-up hand 

sprayer which can be pumped up to 20-30 psi. Use with a fan nozzle to 

apply the acid spray solution. 

B. Purchase food grade Lactic Acid (88%) and/or Peroxyacetic Acid (such as 

Ecolab‘s Inspexx 100). Note that peroxyacetic acid must be stored in a wellventilated, cool area and safety precautions must be observed when 

handling it. 

Step 2 

A. A solution of the chosen organic acid may be mixed directly in the sprayer. 

Be sure to follow the safety precautions given on the MSDS sheet when 

handling the chemicals. 

Accuracy in measuring the acid concentrate is important, so measure the 

acid using a volumetric pipette sufficient to make TWO gallons of solution. 

Measure warm water (120°F) into the sprayer, then add the measured acid 

concentrate, close the sprayer and shake solution to mix thoroughly. Pump 

sprayer according to manufacturer‘s instructions to obtain 20-30 psi 

pressure. 

B. For a 2% LACTIC ACID solution, measure five ounces (5.12 oz or 151.4 

mL) of 88% Lactic Acid and mix into two gallons (7.5 l) of warm water 

(120°F) in the sprayer. Close the sprayer and shake to mix thoroughly. 

Pump sprayer to 20-30 psi. 

C. For PEROXYACETIC ACID 180-200 ppm solution, put on protective gloves, 

apron and eyewear before opening the chemical container to prevent skin 

contact or splashing (see MSDS sheet for other safety precautions). In a 

well-ventilated area, measure two gallons (7.5 l) of warm water (120°F) into 

sprayer. Carefully measure 8-10 mL of peroxyacetic acid using a pipette 

and put into the sprayer. Return remaining peroxyacetic acid concentrate to 

locked chemical storage area. Close sprayer and shake the solution to 

insure thorough mixing. Pump up sprayer to 20-30 psi pressure. 
Step 3 

Following the final carcass wash using a 50 ppm chlorine rinse, spray the hot 

carcass (pork or beef) with the acid spray solution (either lactic or peroxyacetic), 

thoroughly wetting the surface to create some drip. 

Step 4 

After weighing, push the carcasses into the cooler for chilling. 

Note: Prior to spraying carcasses with acid wash, insure that the final rinse 

water contains ≤ 50 ppm chlorine. This assists in controlling microbial 

levels.