Determination of thermal inactivation kinetics (D- and z-values) of Salmonella in brownie batter

Primary Author: Monipel Ansong

Faculty Sponsor: Minto Michael

Primary College/Unit: Agricultural, Human and Natural Resource Sciences

Category: Agricultural and Natural Resource Sciences

Campus: Pullman

Abstract:

Principal Topic: Salmonella can be introduced into bakery products through ingredients such as flour, milk, cocoa powders, and eggs. Studies have shown that Salmonella can survive under adverse environmental conditions over time; therefore, it is vital to study the thermal inactivation kinetics (D- and z-values) of Salmonella in bakery products such as brownie batter. The aim of this study was to determine the D- and z-values of a 5-serovar Salmonella cocktail in brownie batter.

Methods: All-purpose flour was inoculated with a 5-serovar Salmonella cocktail (Enteritidis, Senftenberg, Typhimurium, Montevideo and Newport) and used to prepare brownie batter. This study implemented a randomized complete block design with three replications as blocks. The batter was subjected to heat treatment using thermal-death-time disks in hot water bath at 64, 68, 72 and 76C for 0, 3, 6, 9, 12 min, respectively. The Salmonella population was enumerated using injury-recovery media (brain heart infusion agar overlaid with xylose lysine deoxycholate agar). The graphs for calculating D- and z-values were plotted using Microsoft Excel, and D- and z-values were calculated as absolute values of the inverse of slopes.

Results/implications: The D-values of 5-serovar Salmonella cocktail in brownie batter were 53.4±5.38, 27.2±2.04, 10.7±0.72 and 4.6±0.49 min at 64, 68, 72 and 76C, respectively; whereas, z-value of the Salmonella cocktail was 11.1±0.71C. D-values from this study provide the basic information about the thermal resistance of Salmonella in brownie batter at the start of baking and could help the bakery industry to optimize cooking parameters ensuring the safety of brownies.

Cellulose nanocrystal dispersions protect reproductive buds of tree fruit from cold damage by forming a thermal barrier

Primary Author: Brent Arnoldussen

Faculty Sponsor: Matthew Whiting

Primary College/Unit: Agricultural, Human and Natural Resource Sciences

Category: Agricultural and Natural Resource Sciences

Campus: Pullman

Abstract:

Every year, tree fruit growers lose money from cold damage to reproductive buds or flowers eventually become the future fruit and yield. The Food and Agriculture Organization reported that cold damage has caused more economic losses to crops than any other weather hazard. The potential losses from cold damage are predicted to increase with variable weather patterns resulting from climate change. Cellulose nanocrystals (CNC) represents a new generation of renewable nano-biomaterials, with many unique physical and chemical properties, including their low thermal conductivity. Our team has synthesized a CNC dispersion that can be sprayed onto trees, forming a thin and durable insulating film on the surface of the buds. Thermal image analysis shows apple and cherry buds treated with 3% CNC dispersions lose 16.5% less thermal energy into the environment in cold conditions than the control. As such, analysis of internal freezing events of CNC coated apple buds with digital scanning calorimetry showed that lethal freezing occurred 3.2°C lower than in the control 1 day after application and 5.5°C lower after 3 days. Large scale field test of 2.5% CNC solutions applied using a commercially available orchard sprayer showed that CNC treated trees are given 5.8°C of protection as long as 7 days post application. The results of this work suggest that the use of CNC could represent an advancement in cold damage prevention in fruit crops. The significant and long-lasting protection offered by CNC could allow for a reduction in  economic losses from cold damage

Associative learning of food odors by paper wasps (Hymenoptera: Vespidae)

Primary Author: Megan Asche

Faculty Sponsor: Richard Zack

Primary College/Unit: Agricultural, Human and Natural Resource Sciences

Category: Agricultural and Natural Resource Sciences

Campus: Pullman

Abstract:

Principal topic

Traps and bait stations that utilize attractants can manage paper wasp populations without pesticides. The purpose of this experiment is to test the associative learning behavior of paper wasps and evaluate their level of attraction to three plant-based odors. The hypothesis tested was that wasps exposed to food inoculated with an odor would show a higher level of attraction to that odor than wasps that were not previously exposed.

Methods

Wasps were separated into two groups, “naïve” and “experienced.” Naive wasps were fed an odorless sugar water solution and experienced wasps received a sugar water solution with a 1% concentration of an odor. After the feeding, wasps were placed into a flight tunnel and the level of attraction to the odor was scored.

Results/implications

Strong evidence for associative learning behavior by spring queens and workers has been shown. However, the fall queens and males were less successful. The difference in learning ability between these groups may be because, in nature, spring queens and workers both forage for food, while fall queens and males do not.

This research was funded by U.S. Air Force. Paper wasps form swarms and aggregations on air control towers in late summer and autumn. These wasps can be a hazardous to people and negatively impact equipment. The ability of paper wasps to learn and respond to chemical cues associated with a food may provide an opportunity to manipulate them. These results suggest we can develop a “train and trap” strategy for controlling paper wasps.

Pinpointing regions of the barley genome contributing to hybrid disease susceptibility

Primary Author: Shaun Clare

Faculty Sponsor: Robert Brueggeman

Primary College/Unit: Agricultural, Human and Natural Resource Sciences

Category: Agricultural and Natural Resource Sciences

Campus: Pullman

Abstract:

Principal topic

Barley is an essential ingredient in beer and whiskey. Barley breeding allows for the improvement of barley by crossing two different parents to contribute favorably to offspring for traits such as yield and disease resistance. The increased use of hybrid varieties that possess genes from each parent (heterozygous) rather than favorable genes from either parent (homozygous) has allowed increased yield termed hybrid vigor. However, two lines that are resistant to a disease called net blotch have been shown to be susceptible to the disease when in a heterozygous state. Identifying the mechanism that allows two resistant parents to produce susceptible offspring is important to avoid releasing varieties that do not perform for growers.

Method

To identify the gene responsible for the hybrid susceptibility, ~2000 offspring were propagated with mosaic genomes of each parent. Single nucleotide changes in the genome that are known to be different between each parent were used on the susceptible offspring as a roadmap through the mosaic to pinpoint the region of the genome responsible for susceptibility.

Results/implications

The susceptibility region of the genome has been pinpointed to a five million nucleotide region within the barley genome that contains over five billion nucleotides. Next steps include adding additional markers by sequencing genes and validating which genes in the region are responsible for susceptibility. Removal of this gene will allow for the development of barley varieties that are healthy under disease pressure to ensure secure production of quality barley to feed the beer and whiskey industry.

Effects of water stress on transmission of ‘Candidatus Liberibacter solanacearum’ pathogen by the vector Bactericera cockerelli

Primary Author: Abigail Cohen

Faculty Sponsor: David Crowder

Primary College/Unit: Agricultural, Human and Natural Resource Sciences

Category: Agricultural and Natural Resource Sciences

Campus: Pullman

Abstract:

Principle Topic

Both plant pathogens and insects cause damage to crops and be financially ruinous to growers, and do even more damage when a damaging pest transmits the pathogen. However, environmental factors moderate how plant, pest, and pathogen interact with one another. This experiment looks at how water stress alters potato plant defenses when exposed to the pest Bactericera cockerelli, or potato psyllid. The potato psyllid feeds on solanaceous plants, and pierces plant veins to extract phloem sap. This makes it a capable vector for the bacterial pathogen Candidatus Liberibacter solanacearum (Lso), which causes an economically damaging disease known as zebra chip.

Method

To test the effect of water stress on transmission of the Lso pathogen and potato plant defenses, we exposed potato plants with and without water stress to infected B. cockerelli over 3h, 24h, 28h, and 120 h, while stress-free uninfected plants were used as control. Potato psyllids have a wide range and multiple sub-populations, so we ran the experiment twice, first with the Northwestern sub-population, then with Western.

Results/Implications

These results indicate that water stress in the plant has a negative effect on transmission or circulation of the bacterial pathogen through the plant, in both sub-populations. Furthermore, testing the level of defensive hormones in the exposed plants showed that water stress correlates to higher levels of the hormone associated with defense induction, suggesting that stress primes the plant for infection. This indicates that managed water stress may have the potential to reduce Lso infection in potato plants.

Survival of the quickest: Pathogen pressure drives rapid evolution at a barley resistance gene cluster

Primary Author: Karl Effertz

Faculty Sponsor: Robert Brueggeman

Primary College/Unit: Agricultural, Human and Natural Resource Sciences

Category: Agricultural and Natural Resource Sciences

Campus: Pullman

Abstract:

Principal topic

Net form net blotch (NFNB), caused by the fungal pathogen Pyrenophora teres f. teres (Ptt), results in significant yield loss in effected barley fields worldwide. An important region on barley chromosome 6H has been reported in several studies investigating Ptt resistance and susceptibility. Our group investigated this region, which confers susceptibility or resistance to Ptt, depending on fungal isolate and barley cultivar. Our research has uncovered a unique adaptive mechanism that allows barley plants to rapidly exchange resistance genes in response to pathogen attack.

Method

Using DNA markers, we analyzed three separate barley populations to delimit the 6H region associated with Ptt resistance by correlating marker alleles with disease outcome.

Results/Implications

Our results indicate that the 6H disease resistance cluster covers 3 MB of the genome, containing 36 genes. Of these, four genes resemble disease resistance genes that have been previously characterized. Strikingly, this resistance cluster consistently transfers as a block, with ~5% of individuals from each population harboring a double recombination event where only this block of genes transfers from parent to progeny. The conserved nature of recombination at this site suggests an evolutionary mechanism where the barley plant can rapidly exchange resistance genes in the face of pathogen pressure. This directed recombination bears similarity to mammalian VDJ recombination, an adaptive mechanism allowing for diverse immune responses. The discovery of this mechanism in plants would create a new paradigm for describing host-parasite evolution and breeding for disease resistance.

Whole lentil flours exhibit their highest puffing ability at low processing temperature during extrusion

Primary Author: Pichmony Ek

Faculty Sponsor: Girish Ganjyal

Primary College/Unit: Agricultural, Human and Natural Resource Sciences

Category: Agricultural and Natural Resource Sciences

Campus: Pullman

Abstract:

Principal topic

Extrusion processing is commonly used to produce breakfast cereals and puffed snacks. These products are typically made from cereal flours with a high amount of starch which has high caloric bulk. Lentil is one of the attractive crops that can be used as an alternative ingredient for these products because of their high protein content and bioactive compounds. The source of raw materials including their varieties, can significantly affect the product qualities.

Method

This study was to evaluate the qualities of the puffs made from three varieties of lentils (Brewer, Crimson, and Richlea). Whole seeds of the lentils were ground into flours and then processed with different extrusion processing conditions. Expansion ratio, water absorption index (WAI), and water solubility index (WSI) of the puffs were evaluated. The products with high expansion ratio (high puffing ability) generally provide crispy texture which consumers like. The products with low WAI could be produced as breakfast cereals because they can be crispy longer in milk and the products with high WSI are suitable for the foods for kids and old people.

Results/implications

The three lentils had relatively lower expansion compared to other cereals such as corn, but they exhibited their highest expansion at lower processing temperatures. Richlea variety was found to be the most suitable to produce these puffed products. The product characteristics of Crimson and Brewer varieties were comparable. The result of this study is useful for the food industry to select the lentil varieties for their specific products using extrusion.

Roles of Chickpea Protein (PGIP) in Defense Against Pathogenic Fungi

Primary Author: Vishnutej Ellur

Faculty Sponsor: Weidong Chen

Primary College/Unit: Agricultural, Human and Natural Resource Sciences

Category: Agricultural and Natural Resource Sciences

Campus: Pullman

Abstract:

Plant diseases and pests continue to cause as much as 40% losses during production, storage, and transport of staple crops affecting food security worldwide. Ensuring food security in an environmentally sustainable way is imperative. Over the years, the mainstay of disease management strategies came to rely on the use of pesticides. However, pesticide usage can be detrimental to the environment and continuous use resulted in targeted pathogens developing resistance. Therefore the use of disease-resistant varieties is the most effective and environmentally sustainable approach and it requires plant genes that can produce proteins with pathogen inhibiting properties.

Pathogenic fungi produce several tissue macerating enzymes to penetrate plant tissue and polygalacturonase (PG) being very significant among them. To counteract PGs, plants produce inhibitory proteins called polygalacturonase inhibiting proteins (PGIP). The purpose of this study is to understand the pathogen inhibiting potential of PGIP in chickpea (CaPGIP1). Studying homology, location and expression of any protein is important in understating its role and function. Using a technique called homology modeling we observed that CaPGIP1 contains domains crucial in interacting with pathogen enzymes. Further, its location was investigated using the subcellular localization method and found the protein to be located in the cell wall, a critical defense location of plant proteins. An increased expression of the CaPGIP1 gene was observed when infected with Ascochyta rabiei fungus, using a relative expression technique. These results indicate that chickpea PGIP has a potential role to combat pathogens, our further research will help to gain a better understanding.

Comparison of Microwave-Assisted Thermal Pasteurization and High Pressure Processing as Pasteurization Methods for Green Beans

Primary Author: SUMEYYE INANOGLU

Faculty Sponsor: JumingTang

Primary College/Unit: Agricultural, Human and Natural Resource Sciences

Category: Agricultural and Natural Resource Sciences

Campus: Pullman

Abstract:

There has been an increasing consumer desire for high quality minimally processed food. The food industry is seeking new processing technologies to meet such consumer desire by producing ready-to-eat meals (RTE) with adequate shelf-life. Novel methods such as high pressure processing (HPP) and microwave-assisted pasteurization system (MAPS) can be the good candidates for food industry. The aim is to provide scientific support to food industry about both pasteurization methods.

Based on literature review, the mild pasteurization conditions were selected as 70°C-2 min for MAPS and 600 MPa-10 min at 25°C for HHP, respectively.  For the severe pasteurization, 90°C-10 min was selected for MAPS and 600 MPa-20 min at initial temperature of 45°C were selected for HPP. The quality attributes such as color, chlorophyll content, texture, and pH of green beans were determined at 2°C over 36 days and 10°C over 20 days and at 2°C over 14 weeks and 7°C over 7 weeks for mild and severe pasteurization, respectively.

Similar color change after both pasteurization methods shows that the processing temperature of MAPS did not negatively affect the color of green beans. Severe pasteurization conditions of MAPS and HPP resulted in more loss in green color. The severe MAPS conditions resulted in less retention of firmness in comparison with the severe HPP pasteurization. This can be attributed to the higher processing temperature (90°C), which results in β-eliminative depolymerization of pectin (softening). Microbial growth, mainly acid-producing microorganisms, might be attributed to the decrease in pH and undesirable appearance and smell.