Location: Fruit and Tree Nut Research
2023 Annual Report
Objectives
Determine factors and approaches that impact pecan safety, quality, and marketability of pecans. This includes developing new and improved pecan processing technologies, such as pasteurization and cracking/shelling, for improved storage and safety, while maintaining nutmeat quality and nutrition.
Approach
Developing novel nut shelling and associated processing techniques to minimize physical nutmeat damage, contamination, and loss of quality postharvest; and improving understanding of pre-harvest and postharvest environmental factors that impact pecan color, texture, oil quality, and phytochemical content to identify conditions that maximize duration of quality. To better understand food safety risks associated with pecans, the project will address factors that influence the survival and persistence of foodborne pathogens and identify effective mitigation strategies while maintaining nut quality. In order to maximize marketability, the project will explore means to cost-effectively increase intact pecan meat extraction by modifying parametrized process variables on existing processing equipment.
Progress Report
Note, progress on this project was also captured in the annual report of 6042-21220-014-000D.
A field study was conducted by ARS scientists in Byron, Georgia to determine the transfer of generic Escherichia coli and attenuated Salmonella to inshell pecans during harvest. Data has been collected that evaluated the effects of microbial load, time, and organism on the transfer to inshell pecans during harvest. The study will provide information regarding the potential for pathogen contamination and transfer to inshell pecans during the harvest process and can provide guidance for determining transfer risks.
An industry survey was developed and distributed to gain a perspective on the food safety practices of the pecan shelling industry in the United States. From the conducted survey approximately 26 usable responses were tabulated and evaluated based on the responses from the survey and the correlations with industry practices and how it relates to food safety. The responses from the survey provided insights into industry needs and indicators of food safety practices within the shelling industry. The results will provide valuable insights on how to focus research to meet industry needs.
An experiment was conducted by ARS scientists in Byron, Georgia to evaluate the effectiveness of cold plasma for reducing Salmonella populations on the surface of pecan kernels. The effects of microbial load, distance (4 and 6 cm) to the cold plasma emitter, and treatment times (10 and 20 sec) were evaluated. Preliminary data was conducted to determine how cold plasma frequency influences Salmonella and E. coli reduction on pecan kernels. The results will provide data on cold plasma as a potential non-thermal treatment for pecan kernels.
Studies have been conducted to determine the effectiveness of lactic acid as an effective sanitizer in conditioning water to reduce shiga toxin-producing E. coli populations on the surface of inshell pecans. The effectiveness of lactic acid was compared against chlorine dioxide and hot water sanitizers. Preliminary studies also evaluated the effectiveness of peracetic acid as in conditioning water to reduce Salmonella on the surface of inshell pecans.
Pulsed UV light has been evaluated as an effective tool to inactivate pathogens (Salmonella and E. coli) on pecan halves. The findings suggest that pulsed UV light may be a useful tool for reducing pathogen levels on pecan surfaces. The quality characteristics of treated nuts are being evaluated for color, texture, water activity, moisture content, and changes in lipid oxidation.
Preliminary studies have been conducted evaluating the use of essential oils (from cinnamon bark, clove bud, etc.) in water and surface applications for inshell pecans and pecan kernels for the reduction of Salmonella and E. coli. The results may provide an alternative organic treatment to reduce populations of human pathogens on pecans.
Two nut moisture testing approaches are being explored to improve nut cracking. The first approach leverages non-contact Near-Infrared (NIR) technology, where NIR sensors detect light from the material being measured. NIR enables high-volume moisture measurement, a capability not yet adopted in the agricultural industry, but can yield significant gains by ensuring consistent product quality. The second approach utilizes electrical resistance to convert the electrical properties of the moist pecan into a moisture reading. These real-time measurements will be leveraged to inform nut cracking parameters to increase shell out.
Investigations have been conducted on both established and emerging cracking mechanisms. A Myers Cracker has been used to measure cracking data including force and stress, while also enabling the control of cracker parameters such as displacement and clearance. A circumferential cracker has also been used to facilitate automated control of machine parameters. These real-time data will allow machine adjustments to preferentially generate nut halves or pieces.
Alternative cracking mechanisms that integrate multiple approaches observed in the industry are being explored. One mechanism combines compression and torsion, a technique that has promise, and a machine has been built that integrates compression and torsion.
The operational characteristics of the industry standard 14" sheller continue to be studied. Additional system parameters presently uncontrolled in the industry have been identified as crucial to nut cracking by our research. The sheller, now capable of modifying five different parameters, provides enhanced processing compared to the two-parameter industry standard. The research will provide greater process control during the shelling process.
A state-of-the-art imaging capability has been developed, surpassing the currently available technologies in the industry. The imaging system accurately measures crack performance, accounting for variations introduced by different cracking methods, as well as the shelling process. The measurements obtained are fed back into the equipment to facilitate adjustments. The automated feedback and control continuously learns how parameters impact cracking and shelling performance.
In the pursuit of an entirely automated feedback and control system for cracking and shelling, the adoption of digitization (an Industry 4.0 approach) throughout the process, from moisture tempering to deshelling, has been explored. An assembly line has been outlined, encompassing the collection of data from equipment/sensors and storing it in a cloud-based service for analysis and application to improve and optimize processes. This comprehensive approach enables plant managers to observe trends in pecans and equipment, facilitating informed decision-making.
Accomplishments
