JFS C: Food Chemistry and Toxicology 

Evaluation of High Humidity and Wet Marinade 

Methods for Pasteurization of Jerky 

K. ALLEN, D. CORNFORTH, D. WHITTIER, M. VASAVADA, AND B. NUMMER 

ABSTRACT: The USDA FSIS meat and poultry jerky compliance guidelines recommend a high humidity or liquid 

immersion pasteurization step before drying. The objective of this study was to evaluate the effects of high humidity 

(>90%) or wet marinade pasteurization on jerky characteristics (water activity, moisture/protein ratio, total aerobic 

plate count [TAC]) and sensory properties. Jerky pasteurized by nonmarinade method A (76.6 ◦C dry bulb, 54.4 ◦C 

oven wet bulb temperature for 1 h) had highest sensory scores for spice intensity and interior cured color (redness), 

and generally lower TACs than jerky from marinade pasteurization methods. Jerky pasteurized by method B (54 ◦C 

for 121 min in marinade) had higher TACs than other methods. Approximately 2-log reduction in TAC was observed 

using marinade pasteurization in the smokehouse to internal temperature of 60◦ for 12 min (method C), or in hot 

marinade to internal temperature of 70 ◦C before drying (method D), but jerky was less spicy and somewhat darker 

than jerky from method A. Extruded jerky (1.5-cm thickness) was similar to intact jerky for spice flavor intensity and 

interior redness, but required longer drying time to reach the target Aw of 0.85. Marinade pasteurization by methods 

C or D was feasible, and may be a preferred alternative for some processors, since monitoring of oven humidity 

during pasteurization is not necessary. 

Keywords: humidity, jerky, microbial load, pasteurization, sensory 

C: Food Chemistry & Toxicology 

Introduction 

J

erky is a popular snack item in the United States. Because jerky 

has been heated and dried, it is widely regarded as microbiologically safe. However, gastroenteritis outbreaks have been attributed to consumption of both home-dried and commercially 

prepared jerky (Nummer and others 2004). Between 1966 and 1995, 

8 outbreaks occurred in New Mexico, causing over 250 illnesses. 

Two outbreaks were associated with Staphylococcus aureus, and 

6 were due to contamination with Salmonella (Eidson and others 2000). The cases were primarily traced to local commercially 

prepared jerky, where processing times and temperatures never 

reached a level to destroy pathogens. In 1995, an outbreak of 

E. coli O157:H7 occurred in Oregon, involving home-processed 

deer jerky (Keene and others 1997). Investigators concluded that 

this traditional home-drying jerky process was insufficient to kill 

E. coli O157:H7. 

In 2003, at least 22 cases of salmonellosis were attributed to 

consumption of commercially produced beef jerky in New Mexico 

(ProMED-mail 2003). Twenty percent of the jerky lots tested positive for Salmonella. Although the jerky was dried to a crumbly state 

(Aw < 0.3), investigators concluded that the very slow drying process under low humidity conditions (82 ◦C oven, but only 30 ◦C wet 

bulb temperature) allowed Salmonella organisms to dehydrate during slow drying, and become very resistant to the dry heat. 

A study by Levine and others (2001) also suggested that foodborne pathogens can survive the moderate drying conditions (approximately 60 ◦C) used by commercial jerky manufacturers. Their 

study reported a cumulative prevalence of Salmonella and L. monocytogenes of 0.31% and 0.52% in jerky produced in federally inMS 20060653 Submitted 11/28/2006, Accepted 6/15/2007. Authors are with 

Dept. of Nutrition and Food Sciences, Utah State Univ., 750 North 1200 East, 

Logan, UT 84322-8700, U.S.A. Direct inquiries to author Cornforth (E-mail 

darenc@cc.usu.edu). 

×C 2007 Institute of Food Technologists 

doi: 10.1111/j.1750-3841.2007.00458.x 

Further reproduction without permission is prohibited 

spected plants from 1990 to 1999, even though good manufacturing 

practices were followed and Hazard Analysis Critical Control Point 

plans were in place. 

In response to this issue, the USDA Food Safety and Inspection Service in March 2004 issued a compliance guideline for jerky 

processors, requiring manufacturers who use time–temperature 

guidelines for pathogen destruction to take into account the humidity of the oven, especially in high-altitude areas of the country 

where relative humidity is low (USDA-FSIS 2004). Both wet- and 

dry-bulb thermometer temperatures must be taken during heating/drying, and a difference of 1.67 ◦C between the two indicates 

that oven humidity is less than 90%, and thus insufficient for adequate pathogen kill (Nummer and others 2004). For home-dried 

jerky, USDA recommended cooking beef, pork, venison, and poultry to 71 ◦C followed by drying at 54 to 60 ◦C in a standard homestyle dehydrator (USDA-FSIS 2000). 

As an alternative to the high-humidity initial cook step, processors may heat (cook) jerky in water or marinade to various time– 

temperature combinations sufficient for either 6.5 or 7 log (base 

10) reduction of Salmonella, as specified in the USDA lethality performance standards, Appendix A (USDA-FSIS 2004). After cooking 

following one of the approved time–temperature combinations, the 

jerky can be dried. To verify proper drying, the updated compliance 

guidelines for small and very small jerky processors recommend 

using a laboratory test for Aw (USDA-FSIS 2004). Acidification of 

jerky marinades has also been shown to increase the destruction of 

food pathogens on jerky (Calicioglu and others 2002; Albright and 

others 2003). 

Jerky cooked in high humidity or liquid marinade may have 

altered sensory properties, compared to traditional oven-drying 

practices. Thus, the objective of this study was to compare sensory 

properties (flavor, texture, appearance), microbial load, and water 

activity of jerky prepared by high humidity or wet marinade methods, following USDA guidelines, including 1 oven heating method 

and 3 marinade heating methods (long time/low temperature, 

Vol. 72, Nr. 7, 2007—JOURNAL OF FOOD SCIENCE C351 
Jerky pasteurization. . . 

C: Food Chemistry & Toxicology 

intermediate time/temperature, short time/high temperature). After cooking, jerky was dried at 54 ◦C to a target Aw < 0.85. Preliminary tests also compared Aw measurement by 3 commercial instruments. 

Materials and Methods 

Jerky preparation and marination 

For whole muscle jerky, vacuum packaged, select grade beef pectoral muscles were manually sliced perpendicular to the direction 

of the muscle fibers to 6- to 7-mm thickness. Slices (2.27 kg/batch) 

were then manually mixed with dry spice mix and Prague Powder, using a clean plastic spatula. Personnel wore sterile plastic 

gloves during processing, to minimize bacterial introduction into 

the product during slicing and mixing. For restructured jerky, lean 

beef trim (85:15 visible lean to fat) was used. The lean trim (2.27 

kg/batch) was mixed with spice and cure mix, coarsely ground 

twice through a 9.5-mm grinder plate (Hobart Mfg. Co., Troy, Ohio, 

U.S.A.), and then extruded through a 1.5-cm-diameter stuffing 

horn, using a manual small volume sausage stuffer (F. Dick, Koch 

Supplies, Kansas City, Mo., U.S.A.). 

The spice mix was Heller’s Smoky Beef Jerky Seasoning (hydrolyzed corn protein, corn syrup solids, brown sugar, dextrose, 

natural smoke flavor [lipolyzed butter oil & soy lecithin], maltodextrin, spice, mustard, garlic powder, sodium erythorbate [0.64%], 

onion powder, not more than 2% calcium silicate and calcium 

stearate as anticaking agents). The spice mix was added according to manufacturer’s instructions (3.91 kg spice mix/45.4 kg meat). 

Prague Powder (6.25% sodium nitrite + 93.75% salt) was also added 

(0.113 kg/45.4 kg meat) to obtain 156-ppm initial nitrite level. 

Whole muscle meat slices plus spice mix were held overnight at 

2 ◦C in a covered tray, before heat pasteurization and drying. For 

restructured jerky, the extruded product was prepared immediately 

before pasteurization. 

For nonmarinade pasteurization method A, spice-treated raw 

products were manually placed on stainless steel screens for heating and drying. For marinade pasteurization methods B, C, and 

D, spice-treated products were heated in a marinade consisting of 

1.95 kg commercial spice mix/45.4 kg water. Because of the additional spice mix used to prepare the marinade solution, jerky prepared by marinade pasteurization methods B, C, and D resulted in 

5.86 kg spice mix/45.4 kg meat. 

Jerky pasteurization 

Jerky was cooked (pasteurized) by 1 of 4 methods: 

1. Nonmarinade method A was 76.6 ◦C (170 ◦F) dry bulb, 

54.4 ◦C (130 ◦F) wet bulb oven temperature for 1 h. 

2. B: Cook in marinade at 54.4 ◦C product temperature for 121 

min (long time, low temperature). 

3. C: Cook in marinade at 60 ◦C (140 ◦F) product temperature 

for 12 min (intermediate time and temperature). 

4. D: Cook in marinade at 70 ◦C (158◦F) product temperature 

for 1 s (short time, high temperature). 

Two separate batches of jerky were produced by each method, 

for a total of 8 batches. Method A was recently validated at the Univ. 

of Wisconsin (Buege and others 2006). The marinade methods B to 

D were based on the time/temperature combinations from USDA 

lethality compliance guidelines, Appendix A (USDA-FSIS 2004). In 

preliminary tests, nonmarinade jerky pasteurization was also attempted by holding smokehouse humidity at 90% or greater during 

cooking, by placing a large pan of water in the smokehouse, or by 

regular injection of a water mist, via the smokehouse shower system. With dampers closed, smokehouse humidity was not attained 

C352 JOURNAL OF FOOD SCIENCE—Vol. 72, Nr. 7, 2007 

at cooking temperatures, probably because dampers were not sufficiently tight to retain humidity. 

In nonmarinade method A, spice-treated samples were spread 

on stainless steel screens, placed in the smokehouse (Vortron Inc., 

Beloit, Wis., U.S.A.) with dampers closed, and heated at 76.6 ◦C 

(dry bulb oven temperature). The oven temperature was brought to 

54.4 ◦C wet bulb temperature and held at that temperature for 60 

min. The dry bulb oven temperature was then turned down to 54 ◦C 

for drying, to a target Aw < 0.85. Total cooking and drying time was 

about 5 h. Dry and wet bulb oven temperatures were recorded at 5­

min intervals throughout cooking and drying, using a thermocouple thermometer (Datalogger RTM; Cole-Parmer Instrument Co., 

Vernon Hills, Ill., U.S.A.). Product temperature was recorded continuously, using a strip chart temperature recorder (Dickson, Addison, Ill., U.S.A.). For restructured jerky, the temperature probe 

was inserted longitudinally into the center of extruded product. For 

whole muscle jerky slices, a thick jerky strip (10 mm thick) was prepared for temperature measurement, as described by Ingham and 

others (2005). During heating, the thin strips would have the same 

or higher temperature as the strip used for temperature measurement. 

For marinade methods B and C, spice-treated raw jerky was 

placed between 2 stainless steel screens, and then immersed in 

marinade in a stainless steel pan constructed for this purpose. The 

pan dimensions were 91.4 cm long, 77.5 cm wide, and 10.2 cm 

deep. A drain with manual on/off valve was placed in 1 corner. The 

screens fit snugly inside the pan. The screen dimensions were 86.4 

cm long and 71.1 cm wide. The bottom screen had handles centered 

on each side. The purpose of the top screen was to hold product securely in place while submersed in the marinade. After heating for 

the designated time and temperature, the screens plus jerky were 

lifted out of the marinade and placed on the next higher level of the 

smokehouse truck. The marinade was drained from the pan, and 

the pan was removed from the smokehouse. The smokehouse was 

closed, and the pasteurized jerky was dried at 54 ◦C for an additional 3.5 to 4 h, to a target Aw < 0.85. Jerky product temperature 

was monitored by a thermocouple inserted into the center of a restructured jerky segment, or into a thick jerky slice, as previously 

described. 

For marinade pasteurization method D, spice-treated jerky was 

heated to >70 ◦C by dipping into marinade solution heated to 82 ◦C 

on a portable gas grill (Gasone EZS-1000, Jooan Co. Ltd. Gyeonggido, Korea). Jerky product temperature was monitored by a thermocouple inserted into a jerky slice, as previously described. Marinade 

temperature was also monitored and recorded by a separate thermocouple lead. After jerky strips reached the desired temperature, 

they were removed from the solution and spread on the stainless 

steel screens using sterile disposable forceps (Busse Hospital Disposables, Hauppauge, N.Y., U.S.A.). Jerky was dried at 54 ◦C to a target Aw < 0.85. 

Water activity 

In preliminary experiments, water activity was determined using 3 different instruments: AquaLab Lite water activity meter 

(Decagon, Pullman, Wash., U.S.A.), Hygropalm Aw meter (Rotronic 

Instrument Corp., Huntington, N.Y., U.S.A.), and Aw value meter, (Abbeon Cal, Santa Barbara, Calif., U.S.A.). The Decagon and 

Rotronic units used electric humidity sensors, where water activity (Aw) = equilibrium relative humidity/100. Water activity values 

were completed within 5 min per sample (5 to 10 g) for the Decagon 

and Rotronic units. The Abbeon Cal Aw meter was a less expensive, nonelectronic unit that measured Aw based on the sensitivity 

of a synthetic fiber to changes in relative humidity. Water activity 
 

Jerky pasteurization. . . 

measurements required about 2 h per sample (3 g), to allow humidity in the closed container to reach equilibrium. Water activity 

measurements were then made in triplicate in each instrument using calibration solutions of barium chloride at 0.90 (Abbeon Cal) 

and 6 M sodium chloride, with Aw = 0.76 (Decagon). There were no 

significant differences in Aw measurement among instruments. For 

subsequent Aw measurements on jerky in this study, the Decagon 

AquaLab Lite instrument was used. 

For the Aw measurements on jerky products, means were calculated and compared by ANOVA for the main effects of jerky type 

(whole or ground), pasteurization method (A, B, C, or D) and their 

interaction, using StatisticaTM (Statsoft Inc., Tulsa, Okla., U.S.A.). All 

analyses were performed in duplicate. 

Moisture and protein 

To calculate moisture protein ratio (MPR), jerky samples were 

analyzed in duplicate for percent moisture (AOAC 1990, method 

950.46b) and protein by the Kjeldahl method (AOAC 928.08). MPR 

was calculated as the average percent moisture divided by the average percent protein for each jerky sample. 

Preparation of samples for 

microbiological examination 

Raw marinated meat was sampled after the marination step 

was complete. Samples (15 to 20 g) were placed directly into a 

preweighed stomacher bag. Dried samples were taken from the 

smoke house using sterilized tweezers, and were transferred immediately to preweighed stomacher bags. The bags were then 

weighed, and the weight of the marinated meat or jerky was 

recorded. Raw marinated sample weights ranged from 15 to 20 g, 

while cooked jerky weights were 10 to 15 g. To the stomacher bag, 

99-mL sterile Butterfield’s phosphate diluent was added. Samples 

were then processed for 60 s at medium speed on a Seward Stomacher 400 (Norfolk, U.K.). All subsequent dilutions were made using 

sterile Butterfield’s phosphate diluent. 

Microbiological examination of samples 

Microbiological examination of samples was done to determine 

the relative efficacy of pasteurization methods A to D. Total aerobic 

counts (TACs) and total enterobacter counts (TECs) of raw marinated and cooked jerky samples were performed using Petrifilm 

plates (3M Corp., St. Paul, Minn., U.S.A.). One milliliter of the stomached/diluted sample was plated in duplicate on appropriate Petrifilm, according to manufacturer directions. Samples were incubated for 24 h at 35 ◦C for TEC (American Public Health Assn.), and 

48 h at 35 ◦C for TAC (AOAC method 990.12). Colonies were enumerated according to manufacturer directions. 

Sensory panel training 

Ten panel judges (USU faculty, staff, and students, 21 to 60 y 

old) were recruited and trained in 2 training sessions. During training session 1, panelists were given samples representing anchor 

points for each attribute. For spice flavor intensity, a hot, flavorful, locally produced jerky was used as an example of “5, extremely 

intense”, and a jerky produced in the USU meat lab using half 

the normal spice level was used as an example of “2, slightly intense”. Cohesiveness was of interest primarily in the ground, extruded product. A commercially available extruded kippered product was used for “5, extremely cohesive”, and a Vienna-type sausage 

was used for “1, not cohesive”. Toughness anchor point “4, very 

tough” was represented by a commercial jerky product, and “1, not 

tough” by an extruded stick-type product. Anchor points for surface darkness were a dark brown commercial jerky product (“4, 

very dark”) and a light, kippered beef product which was more red 

than brown (“2, slightly brown”). Cured color intensity/redness examples were an intensely red, commercially available pepperoniflavored sausage product (“5, extremely red”), and a brown jerky 

product with slight redness visible in the fibers when pulled apart 

(“2, slightly red”). Final anchor point ratings were decided upon 

by the entire training panel after initial evaluation and group 

discussion. 

During training session 2, judges were provided with the same 

anchor points as given in session 1 to allow them to reorient themselves. After a brief discussion and an explanation of the typical ballot layout, judges were sent to panel booths for a trial sensory evaluation. Three coded jerky samples, consisting of duplicate samples 

of treatment A and a single sample of treatment D, were given to 

judges. Ballots were then evaluated for consistency, both within (individual ratings of the duplicate treatment A samples) and between 

judges (group ratings of treatment A and treatment D). Based on 

these results, no further training sessions were provided, and no 

judges were excluded from subsequent sensory evaluations. 

Sensory evaluation 

Due to microbial safety concerns, treatment B was excluded 

from sensory evaluation. Jerky samples were rated by a trained taste 

panel (n = 10) for spice flavor intensity, cohesiveness, toughness, 

surface darkness, and cured color intensity (redness). A rating scale 

of 1 to 5 was used for each attribute, with 1 = none/not observed, 

2 = slight, 3 = moderate, 4 = very, 5 = extreme. Samples were cut no 

more than 30 min prior to the sensory evaluation and pieces were 

held in zippered plastic bags to prevent drying. Samples were presented to judges in individual booths under fluorescent light. Water 

and spit cups were provided to each judge, and anchor point examples were provided when requested. Two evaluations (on separate 

days) were conducted for whole muscle jerky, and 1 evaluation for 

ground jerky. Panel scores were evaluated statistically for main effects of treatment and judge using the proc glm function of SAS version 9.0 (SAS Inst. Inc., Cary, N.C., U.S.A.). Separation of means was 

performed using the Tukey adjustment for multiple means comparisons at a significance level of P ≤ 0.05. 

Results and Discussion 

Water activity (Aw) was affected (P = 0.006) by jerky type (intact or extruded) and by pasteurization method (Table 1 

and 2, respectively). Extruded jerky had higher Aw than intact 

jerky, even though extruded jerky was dried—1 to 2 h longer—after 

Table 1 --- Water activity of cooked and dried product as 

affected by meat type 

Meat type N Aw 

Intact slices (whole) 8 0.838 b 

Extruded (ground) 8 0.857 a 

P-value 0.006 

Table 2 --- Water activity of cooked and dried product as 

affected by pasteurization method 

Pasteurization methoda N Aw 

A 4 0.854 ab 

B 4 0.866 a 

C 4 0.842 bc 

D 4 0.830 c 

P-value 0.006 

aA = 76.6◦C dry bulb and 54.4 ◦C wet bulb for 1 h; B = 54.4 ◦C for 121 min in 

marinade; C = 60 ◦C for 12 min in marinade; and D = 70 ◦C for 1 s in marinade. 

Vol. 72, Nr. 7, 2007—JOURNAL OF FOOD SCIENCE C353 

C: Food Chemistry & Toxicology 
1.00 

0.95 

:s: 0.90 <( 

0.85 

0.80 

30% 

♦ 

40% 

♦ 

♦ 

y = -0.6934x2 + 1.0126x + 0.5843 

R2 = 0.7603 

50% 60% 70% 

Moisture Content(%) 

♦ 

Jerky pasteurization. . . 

C: Food Chemistry & Toxicology 

pasteurization than intact jerky, in order to approach the target 

Aw of 0.85. This was probably due to the relatively large diameter 

(1.5 cm) of the extruded jerky. A smaller diameter extruded jerky 

would likely dry faster. The interaction of jerky type and pasteurization method did not significantly affect Aw (Table 3). 

Jerky pasteurized by method D (rapid heating in hot marinade) 

had lower Aw (P = 0.006) than jerky from methods A or B (nonmarinade and long-time, low-temperature marinade pasteurization, respectively; Table 2). Extruded jerky pasteurized by long 

time, low temperature method B exhibited characteristics of “case 

hardening”, including dry surface but a relatively moist interior, 

contributing to the higher Aw of jerky prepared by this method 

(Table 2). Values for MPR were also higher than 0.75 for extruded 

jerky pasteurized by methods A, B, and C, but intact jerky from 

these pasteurization treatments had MPR < 0.75 (Table 3). Dried 

meats with MPR > 0.75 cannot be labeled “jerky”, according to the 

FSIS Food Standard and Labeling Policy Book (DeHoll 1981). However, dried meats with MPR ≤ 2.03:1 may be labeled “kippered” (DeHoll 1981). MPR < 0.75 and Aw < 0.85 were obtained in extruded 

jerky from pasteurization method D, where meat was immersed in 

hot marinade to rapidly attain an internal temperature >70 ◦C, then 

placed in the smokehouse for drying (Table 2 and 3). 

After pasteurization, Aw and moisture content were monitored 

for all treatments at 30 min intervals initially, and 1-h intervals during the later stages of drying (Figure 1). Immediately after pasteurization, Aw values were as high as 0.95, with greater than 70% moisture content. At the end of the drying period, Aw values were as low 

as 0.82, with < 35% moisture content (Figure 1). There was a polyTable 3 --- Water activity and moisture/protein ratio of 

cooked product as affected by the interaction of pasteurization methoda and meat type 

Pasteurization Meat Moisture/ 

method type N protein ratio Aw 

A Intact 2 0.49 0.852 

A Extruded 2 0.769 0.857 

B Intact 2 0.58 0.849 

B Extruded 2 0.783 0.884 

C Intact 2 0.467 0.840 

C Extruded 2 0.780 0.844 

D Intact 2 0.581 0.825 

D Extruded 2 0.447 0.846 

P-value 0.116 

aA = 76.6◦C dry bulb and 54.4 ◦C wet bulb for 1 h; B = 54.4 ◦C for 121 min in 

marinade; C = 60 ◦C for 12 min in marinade; and D = 70 ◦C for 1 s in marinade. 

Figure 1 --- Relationship between water activity (Aw) and 

moisture content of jerky during drying. Measurements 

were taken at intervals after pasteurization by methods 

A to D. Products were dried to a target Aw of 0.85. 

C354 JOURNAL OF FOOD SCIENCE—Vol. 72, Nr. 7, 2007 

nomial relationship between Aw (y-axis) and moisture content (xaxis), with a correlation coefficient of 0.76. Thus, there was a strong 

positive relationship between Aw and moisture content. However, 

the relationship was not sufficiently high to be useful for predictive purposes. For 35% to 40% moisture samples, some samples 

had Aw as high as 0.93, while other samples had Aw < 0.85. Since 

rapid methods exist for both Aw and moisture, processors may 

obtain equipment for either or both measurements, as suits their 

needs. 

TACs and total Enterobacteriaceae counts (TECs) were determined on spice-treated raw treatments A to D immediately before 

pasteurization and again after pasteurization and drying (Table 4), 

to compare effectiveness of the various heat treatments against the 

indigenous microflora. This is not a food pathogen lethality study, 

and the results presented here cannot be used in that context. In 

run 1, raw samples had lower TAC of 103 to 104, while raw samples 

in run 2 had TAC of 104 to 106. In run 1, a single sample from treatment B (low temperature, long time pasteurization) tested positive for Enterobacteriaceae after pasteurization and drying. In run 

2 with high initial bacterial load, extruded jerky from marination 

Table 4 --- Total aerobic count (TAC) and total Enterobacteriaceae (TEC) of cooked product as affected by pasteurization method (A to D) and initial microbial load 

Run 1 Run 2 

Low raw marinated count High raw marinated 

count (103 to 104) count (104 to 106) 

Treatmenta TAC TEC TAC TEC 

A 

Intact 5.3 × 100 ND 2.7 × 100 ND 

Extruded 1.5 × 102 ND ND ND 

B 

Intact 5.3 × 102 4.5 × 100 5.6 × 103 ND 

Extruded 8.9 × 101 ND 8.8 × 103 ND 

C 

Intact 2.7 × 101 ND 4.7 × 102 ND 

Extruded 2.8 × 101 ND 3.9 × 103 ND 

D 

Intact 1.5 × 101 ND 2.9 × 102 ND 

Extruded 1.4 × 101 ND 4.6 × 103 ND 

aSee Table 2 for treatment descriptions. 

ND = No colonies detected (<10 CFU/g). 

Table 5 --- Mean sensory scores by meat type 

Interior 

Meat Spice Surface cured 

type intensity Cohesiveness Toughness darkness color 

Intact 2.43 a 3.93 a 3.53 a 3.90 a 2.60 a 

Extruded 2.33 a 3.07 b 2.77 b 3.23 b 2.90 a 

P-value 0.655 0.001 0.001 0.002 0.133 

Values in a column sharing letters are not different (P > 0.05). 

Intensity scale 1 to 5; 1 = not intense; and 5 = extremely intense. 

Table 6 --- Mean sensory scores by treatment 

Interior 

Meat Spice Surface cured 

type intensity Cohesiveness Toughness darkness color 

A 2.85 a 3.45 a 3.00 b 2.85 b 3.45 a 

C 2.05 b 3.45 a 2.75 b 4.15 a 2.35 b 

D 2.25 ab 3.60 a 3.70 a 3.70 a 2.45 b 

P-value 0.014 0.848 0.002 <0.001 <0.001 

aSee Table 2 for treatment descriptions. 

Values in a column sharing letters are not different (P > 0.05). 

Intensity scale 1 to 5; 1 = not intense; and 5 = extremely intense. 
Jerky pasteurization. . . 

methods B, C, and D all had TAC of 103 after heating and drying. 

In run 2 (high raw microbial load), jerky pasteurized by nonmarinade method A (76.6 ◦C dry bulb, 54.4 ◦ wet bulb oven temperature for 1 h) had generally lower total aerobic microbial counts 

than jerky from marinade pasteurization methods. When these 

conditions were achieved, the product temperature was high (70 to 

74 ◦C), resulting in a substantial reduction in microbial load. 

Pasteurization treatment B, where product internal temperature 

was held at 54.4 ◦C for 121 min (low temperature, long time) is 

one of the lowest temperature treatments approved for jerky processing, based on Appendix A of the USDA compliance guidelines 

(USDA-FSIS, 2004). The time–temperature guidelines for 6.5- to 

7.0-log reduction of Salmonella, as listed in Appendix A, were based 

on a thermal death time study for Salmonella in beef emulsions in 

tubes (Goodfellow and Brown 1978). Perhaps the expected bacterial lethality was not observed in this study because TAC results included bacteria other than Salmonella that may be more heat resistant. Also, the jerky in this study contained substantial fat and 

added sugars that are known to increase bacterial heat resistance 

(Goepfert and others 1970), compared to the lean beef emulsions 

used by Goodfellow and Brown (1978). Whatever the explanation, 

results of this study indicate that a time–temperature combination 

of 54.4 ◦C for 121 min did not adequately reduce bacterial numbers 

in extruded or intact jerky. 

Because of the high bacterial counts remaining after pasteurization, and the survival of an Enterobacter (the family than includes 

Salmonella and E. coli O157:H7), pasteurization method B was not 

served to sensory panelists. Jerky served to panelists was only from 

replication 1 for treatments A, C, and D (Table 4), where TAC of final dried product was 100 to 102. Samples were vacuum bagged and 

stored frozen ( 10 ◦C for < 1 mo) prior to sensory panel evaluation. 

Predictably, panel sensory scores of jerky were affected by meat 

type (intact or extruded). Intact jerky had higher (P < 0.05) cohesiveness, toughness, and surface darkness than extruded jerky 

(Table 5). In comparison of pasteurization methods, spice intensity was higher (P < 0.05) for jerky from nonmarinade treatment 

A, compared to marinade treatment C. Toughness was higher (P <

0.05) for method D jerky. Surface darkness was higher and red interior cured color was lower (P < 0.05) for marinade-pasteurized jerky 

(treatments C, D), compared to jerky from treatment A (Table 6). 

Thus, marinade pasteurization of jerky altered product appearance, and in some cases reduced spice flavor intensity, compared 

to nonmarinade pasteurized jerky (method A). 

Conclusions 

Recent USDA-FSIS guidelines for jerky manufacture recommend that processors use a validated pathogen lethality process or an approved time–temperature heat treatment in the presence of 90% or greater humidity to ensure product safety. In 

preliminary studies, 90% humidity could not be obtained in our 

smokehouse during heating. However, some marinade pasteurization methods were feasible, and may be a preferred alternative 

for small processors, since monitoring of humidity during heating is not necessary. Because marinade pasteurization of jerky altered sensory properties, it is recommended that processors using a marinade pasteurization method conduct sensory testing to 

optimize spice levels. Also, the long time/low temperature combinations listed in Appendix A of the USDA time–temperature tables for heat inactivation of pathogens may not adequately control 

spoilage organisms. It is recommended that processors confirm the 

efficacy of long time/low temperature marinade heating processes 

with their own products. 

Acknowledgments 

The authors thank the USDA Food Safety and Inspection Service 

and the Utah Agricultural Experiment Station for their financial 

support of this study. This manuscript is Utah Agric Experiment 

Station paper nr 7857. 

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