Progress 09/01/05 to 12/31/08
Outputs
OUTPUTS: Heat treatment of food-processing facilities involves using elevated temperatures (46 to 60oC for 24 h) for management of stored-product insects. Heat treatment is a viable alternative to the fumigant methyl bromide, which is phased out in the United States as of 2005 because of its adverse effects on the stratospheric ozone. However, very little is known about responses of the cigarette beetle, a pest associated with food-processing facilities, to elevated temperatures. The main research objectives were to evaluate stage-specific susceptibility of the cigarette beetle to elevated temperatures to identify the most heat tolerant stage. The cigarette beetle is a pest commonly associated with processed foods, spices, pasta plants, warehouses, and retail stores. Previous research has shown stage-specific susceptibility of red and confused flour beetles, and the Indianmeal moth. Very little is known about the susceptibility of cigarette beetle to elevated temperatures. Therefore, laboratory tests were conducted to identify the most heat tolerant stage of this species and also determine minimum temperature-time combinations for complete control of the most heat tolerant stage. PARTICIPANTS: The project director for the project was Dr. Bhadriraju Subramanyam. Others that contributed to the project include Dr. Xingwei Hou, a postdoctoral research associate of Dr. Subramanyam. This work was used to confer a MS degree to Mr. Chun Yu. TARGET AUDIENCES: The primary target audience served by the project includes food industry stakeholders seeking alternatives to methyl bromide fumigation. In addition, this work is also valuable to companies that provide heat treatment service to the food industry, such as manufacturer's of the heating equipment and pest management professionals that offer this service to their clients. Information to the target audiences was shared through in informal conversations and at professional and trade meetings. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
In the present investigation, eggs, young larvae, old larvae, pupae, and adults of the cigarette beetle were exposed to 46, 50 and 54oC, and 25% RH. The elevated temperatures tested (≥46oC) were well above the optimum range (28-32oC) for development and survival of this species. Although 50oC is the minimum temperature required for effective disinfestation, vertical and horizontal stratification of temperatures during heat treatment may result in temperatures below or above 50oC in some portions of the facility. Therefore, temperatures between 46 and 54 degrees Celsius were selected for this study. Clear cut susceptibility differences among eggs, young larvae, old larvae, pupae, and adults were observed at 46oC, but at 50 and 54oC differences among certain stages disappeared because of increased susceptibility of stages. However, eggs were always significantly less susceptible when compared with other stages at each of the temperatures. These experiments also confirmed eggs to be the most heat tolerant stage. The natural (control) mortality at 46, 50, and 54oC based on egg hatchability was 17 to 18%, and that based on egg-to-adult emergence was 14 to 15%. In general, the intercepts, slopes, and lethal time estimates at each of the three temperatures based on the two approaches (egg hatchability and egg-to-adult emergence) for egg mortality assessment were very similar. The lethal time estimates decreased with an increase in temperature. Irrespective of the mortality assessment method used, the lethal time estimates (LT50 and/or LT99) are 3 to 6-fold lower at 50oC when compared to 46oC and 4 to 5-fold lower at 54oC when compared to 50oC. Lethal ratio tests indicated that differences between the LT99 values based on egg hatchability and egg-to-adult emergence at each of the elevated temperatures were not significantly different from one another, but the LT99 values between any two elevated temperatures based on egg hatchability or adult emergence were significantly different from one another. These results indicated that approximately 10 h are needed to kill 99% of the cigarette beetle eggs at 46oC, 3 h at 50oC and about 0.6 h at 54oC.
Publications
- Boina, D., Subramanyam, Bh., and Alavi, S. 2008. Dynamic model for predicting survival of mature larvae of Tribolium confusum during facility heat treatments. Journal of Economic Entomology, 101: 989-997.
|
Progress 09/01/07 to 08/31/08
Outputs
OUTPUTS: Heat treatment, an 100-year-old technology, involves raising the ambient temperature of a food-processing facility to 50-60 degrees Celsius and holding these elevated temperatures for 24-36 hours. A heat treatment can be optimized by determining the minimum amount of heat energy required to raise and maintain elevated temperatures, eliminating cool spots, and determining the degree and duration of insect suppression obtained. Gauging heat treatment effectiveness against insects through bioassays and population monitoring are some methods to determine the degree and duration of insect suppression. Optimization methods explored in this research include predicting and validating heat energy requirements in commercial facilities, monitoring temperature profiles among locations, and evaluating heat treatment effectiveness through bioassays. In three facilities (pasta plant, pet food facility, and breakfast cereal manufacturing facility) real-time temperatures during heat treatment were monitored with single or 4-channel temperature sensors data loggers. For bioassays, vials with screen lids containing 2.5 g of wheat flour and 30 adults or 30 first instars of the red flour beetle were used. Vials were placed on the floor and removed at various times during treatment. All vials were incubated at 28 degrees celsius and 60 percent RH to assess mortality. Adult mortality was assessed after 24 h, whereas larval mortality was based on number of adults that emerged out of the total exposed after 4 wk. In the pasta plant total heat energy requirements for both rooms were predicted using Heat Treatment Calculator (HTC) developed at Kansas State University, based on starting temperature, target temperature, duration of heat treatment, and heat loss through exposed surfaces, steel, and infiltration. These predictions were compared with the actual amount of heat energy consumed during the heat treatment from gas consumption logs provided by the company, given 70 percent efficiency of the boiler and the price of natural gas as of July 1, 2007. In the pet food facility, heat treatment was conducted during winter (outside ambient temp., -12 degrees C) for 23 h with 4 Hot Breath Heaters (Model CAQ-202-HS-T12, Armstrong Int'l., MI). For bioassays, Bug-Chek cards (LSB Products, KS) with 10 red flour beetle adults each were placed at 1 m above the floor at locations indicated in Fig.1. The mortality of adults in Bug-Chek cards was compared with that in vials that were placed on the floor. In the breakfast cereal facility, heat treatment was conducted during June, July, and September using steam heaters that were regulated manually when temperatures were >60 degrees celsius or <50 degrees celsius. Data loggers were used to monitor temperatures of floor surfaces and in areas that may be potential refugia for insects (floor cracks and crevices, inside spouts, and within pieces of equipment). PARTICIPANTS: Nothing significant to report during this reporting period. TARGET AUDIENCES: Food industry quality assurance/quality control, and food processing facility managers. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
In general, temperature profiles varied by locations, and the floor temperatures were greater than the temperatures in potential insect refugia. HTC appeared to be a useful tool for determining heat energy requirements and costs, because the predicted and observed values were in close agreement. Heat treatment duration can be reduced to less than 24 h as shown in facility A. In less than 16 h, 100 percent mortality of adults and heat-tolerant first instars was observed in facility C where temperatures raised quickly to 50 degrees celsius or above in less than 15 h. The winter heat treatment in facility B was not efficient because the mean temperature never reached 50 degrees celsius and the mean mortality of red flour beetles in vials was <20 percent. The Bug-Chek cards are frequently used by the industry to gauge treatment effectiveness. The 100 percent mortality of adults in Bug-Chek cards in facility B compared to <20 percent in vials suggested that mortality based on Bug-Chek cards should be interpreted with caution.
Publications
- Beckett, S. J., P. G. Fields, and Bh. Subramanyam. 2007. Disinfestation of stored products and associated structures using heat, pp. 182-237. In Tang, J., E. Mitcham, S.Wang, and S. Lurie (Eds.), Heat treatments for postharvest pest control: theory and practice, CAB International, Oxon, UK.
|
Progress 09/01/06 to 09/01/07
Outputs
A pasta facility was heat treated during July 1-2, 2006. The flour room volume was 120,000 cubic feet; the press room was 1.55 million cubic feet. Commercial food and pheromone baited traps were placed to monitor red flour warehouse, and cigarette beetles in both rooms. There were 35 traps in the press room, 10 in the flour room, and 5 outside the facility. Traps were checked biweekly before and after the heat treatment. Heat treatment lasted 16-17 hours. HOBO temperature-logging devices, placed in various locations, were used to measure temperatures. Temperatures from HOBO units were averaged for each room to determine ambient temperature, time taken to attain 122 degrees Fahrenheit and time temperatures were above 122 degrees Fahrenheit. These values were entered into the KSU's Heat Treatment Calculator, along with the room measurements, to estimate the heat energy (in British Thermal Units) required. The actual heat energy used was obtained from the amount of
natural gas consumed during the 16-17 hours of heat treatment from company gas usage logs. Results showed that the difference in the maximum temperatures reached among the 12 units in the flour room was 86 degrees Fahrenheit. The temperature was above 122 degrees Fahrenheit for only 4.1 hours in one location and above 16 hours in another location. Difference in the maximum temperatures reached among the 33 HOBO units in the press room was 54 degrees Fahrenheit. In 3 locations temperatures did not reach 122 degrees Fahrenheit. Average temperature profiles indicated that the ambient temperature in both the rooms was 86 degrees Fahrenheit. The average target temperature (where temperature levels off) in the flour room was 146 degrees Fahrenheit and in the press room was 135 degrees Fahrenheit. The rise phase was 8 hours in both rooms and the hold phase was 8 hours in the flour room and 9 hours in the press room. These values with our Heat Treatment Calculator gave a total of 160.8
million British Thermal Units with an estimated fuel cost of $ 2,498. The actual heat energy used was 155 million British Thermal Units and the actual fuel cost, based on 2,212 Therms of natural gas consumed, was $ 2,411. In the press room, red flour beetles captured per trap per week prior to heat treatment ranged from 0.32 to 0.46 adults. In the flour room it ranged from 0.40 to 0.65, and outdoors it ranged fro 0 to 0.65. Trap captures immediately after the heat treatment showed 100% reduction in the press room and 86% reduction in the flour room. These captures remained low (less than 0.1 adult per trap per week) until the last collection date of August 23, 2006. Outdoor captures after heat treatment fluctuated at 0.20 to 0.50 adults per trap per week. Warehouse beetles were present in both the flour (0.05 to 1.62 adults per trap per week) and press rooms (0.34 to 47 adults per trap per week). Reduction in trap captures was 100% in the flour room and 91% in the press room, and
captures remained low until the end of trapping (0-0.20 adults per trap per week). Outdoor captures were high throughout the collection period (18.9 to 69.8 adults per trap per week).
Impacts
The Heat Treatment Calculator, developed at K-State, is a powerful tool to determine heat energy requirements and the cost of a heat treatment. Our estimated values were in close agreement with actual values obtained from company data. We also showed the effectiveness of heat treatment by using traps. Heat treatment is a viable methyl bromide alternative and work in 2007 in different commercial facilities will provide additional data needed to support this technology. We did not use the model we developed to predict survival of the most heat tolerant stage of red flour beetle (young larvae that hatch from eggs) from the temperature profile data we obtained with the HOBO data-logging units. However, this work will be done in 2007. The model is a powerful tool to predict insect survival just from temperature data alone. Since we have temperature data from various locations, we will be able to estimate survival of young larvae of red flour beetles from these data using
our novel model. That method offers a safe animal free method to control insects in food processing and milling plants.
Publications
- Dosland, O., Bh. Subramanyam, G. Sheppard, and R. Mahroof. 2006. Temperature modification for insect control, pp. 89-103. In, Heaps, J. (Ed.), Insect Management for Food Storage and Processing. Second Edition, American Association of Cereal Chemists, St. Paul, Minnesota.
- Mahroof, R., and Bh. Subramanyam. 2006. Susceptibility of Plodia interpunctella (Hubner) (Lepidoptera: Pyralidae) to high temperatures used during structural heat treatments. Bulletin of Entomological Research 97: 1-7.
|
Progress 09/01/05 to 08/31/06
Outputs
Four facilities, one in Fresno, California, one in St. Louis, one in Nebraska, and one in Illinois, were identified for validating the Heat Treatment Calculator, for measuring temperatures attained during heat treatment and consequent survival of flour beetles in test cages, and for trapping resident stored-product insects six weeks before and 24 weeks after a heat treatment. All four facilities plan to conduct heat treatments during the spring and summer of 2006.
Impacts
The amount of heat energy required for heating a facility, determining the time to stop heat treatments based on insect survival, and gauging heat treatment effectiveness are three areas that need to be studied to optimize heat treatments. Currently there is no information on these aspects from commercial food processing facilities. Our work will provide quantitative information that can be used to compare the cost-effectiveness heat treatments relative to methyl bromide fumigation.
Publications
- No publications reported this period
|
|