Influence of radio frequency treatment on in-shell walnut quality and Staphylococcus aureus ATCC 25923 survival

Zhang, Lihui; Lyng, James G.; Xu, Ruzhen; Zhang, Shuang; Zhou, Xu; Wang, Shaojin

doi:10.1016/j.foodcont.2019.03.030

Cited by 41 publications

(10 citation statements)

References 40 publications

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“…For obtaining walnut kernels and shells with different levels of MC for further determining dielectric properties, four MC levels of 8%, 12%, 16%, and 20% (d.b.) were chosen as target MCs of whole walnuts based on the pasteurization treatment and a MC of 8%, which is qualified for long-term storage of walnuts in the ambient environment [ 11 , 29 ]. Distilled water with different pre-calculated quantities was added to the polyethylene bags with in-shell walnuts to adjust the MCs to the target ones.…”

Section: Methodsmentioning

confidence: 99%

“…To ensure the tight contact between the probe and samples to eliminate air gaps, kernels and shells of five stochastically selected walnuts were milled into powders, and about 12 g samples were put into the sample test cell (21 mm diameter × 50 mm height) and compressed into cylinders prior to experiments. Temperatures from 20 to 80 °C with an interval of 10 °C were adopted based on the maximal range commonly used for pasteurizing in-shell walnuts [ 11 ]. The temperature of samples was monitored by a thermocouple (HH-25 TC, Type-T, OMEGA Engineering Inc., Stamford, CT, USA) and maintained at selected levels by the oil bath.…”

Section: Methodsmentioning

confidence: 99%

“…Dielectric heating, including radio frequency (RF) and microwave (MW) treatments, raises temperatures of materials quickly and volumetrically since the heat generates inside products by dipole rotation and ionic migration as subjected to an alternating electromagnetic (EM) field [ 8 ]. Owing to the rapid heating, shortened processing duration, maintained product quality, and no chemical residues, the RF and MW treatments have been studied as novel pasteurization methods for nuts and other agricultural products, such as hazelnuts [ 9 ], green beans [ 10 ], walnuts [ 11 ], and paprika [ 12 ]. RF wave is more suitable for the treatment of bulk and thick materials because of the more uniform heating caused by the larger penetration depth as compared with MW processing [ 13 ].…”

Section: Introductionmentioning

confidence: 99%

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Temperature and Moisture Dependent Dielectric and Thermal Properties of Walnut Components Associated with Radio Frequency and Microwave Pasteurization

Mao

Hao

Guan

et al. 2022

Foods

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To provide necessary information for further pasteurization experiments and computer simulations based on radio frequency (RF) and microwave (MW) energy, dielectric and thermal properties of walnut components were measured at frequencies between 10 and 3000 MHz, temperatures between 20 and 80 °C, and moisture contents of whole walnuts between 8.04% and 20.01% on a dry basis (d.b.). Results demonstrated that dielectric constants and loss factors of walnut kernels and shells decreased dramatically with raised frequency within the RF range from 10 to 300 MHz, but then reduced slightly within the MW range from 300 to 3000 MHz. Dielectric constant, loss factor, specific heat capacity, and thermal conductivity increased with raised temperature and moisture content. Dielectric loss factors of kernels were greater than those of shells, leading to a higher RF or MW heating rate. Penetration depth of electromagnetic waves in walnut components was found to be greater at lower frequencies, temperatures, and moisture contents. The established regression models with experimental results could predict both dielectric and thermal properties with large coefficients of determination (R2 > 0.966). Therefore, this study offered essential data and effective guidance in developing and optimizing RF and MW pasteurization techniques for walnuts using both experiments and mathematical simulations.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Temperature and Moisture Dependent Dielectric and Thermal Properties of Walnut Components Associated with Radio Frequency and Microwave Pasteurization

Mao

Hao

Guan

et al. 2022

Foods

Self Cite

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“…The detailed information about TDT HBS can be found in other studies [ 30 , 31 ]. In this study, all heating conditions were conducted at a fixed heating rate of 5 °C/min to simulate the fast-heating rate commonly used in radio frequency pasteurization treatments [ 33 , 42 ].…”

Section: Methodsmentioning

confidence: 99%

Effect of Physical Structures of Food Matrices on Heat Resistance of Enterococcus faecium NRRL-2356 in Wheat Kernels, Flour and Dough

Lin

Zhu

Zhang

et al. 2020

Foods

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Nonpathogenic surrogate microorganisms, with a similar or slightly higher thermal resistance of the target pathogens, are usually recommended for validating practical pasteurization processes. The aim of this study was to explore a surrogate microorganism in wheat products by comparing the thermal resistance of three common bacteria in wheat kernels and flour. The most heat-resistant Enterococcus faecium NRRL-2356 rather than Salmonella cocktail and Escherichia coli ATCC 25922 was determined when heating at different temperature–time combinations at a fixed heating rate of 5 °C/min in a heating block system. The most heat-resistant pathogen was selected to investigate the influences of physical structures of food matrices. The results indicated that the heat resistance of E. faecium was influenced by physical structures of food matrices and reduced at wheat kernel structural conditions. The inactivation of E. faecium was better fitted in the Weibull distribution model for wheat dough structural conditions while in first-order kinetics for wheat kernel and flour structural conditions due to the changes of physical structures during heating. A better pasteurization effect could be achieved in wheat kernel structure in this study, which may provide technical support for thermal inactivation of pathogens in wheat-based food processing.

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“…MW heating and RF heating have also been studied for the drying of tree nuts (Wang et al, 2014;Zhou & Wang, 2019). Both MW (wavelength range: 300 MHz to 300 GHz) and RF (3 kHz to 300 MHz) are electromagnetic waves that can penetrate the foods.…”

Section: Fu Et Al 2016mentioning

confidence: 99%

Postharvest processing of tree nuts: Current status and future prospects—A comprehensive review

Chen

Pan

2022

Comp Rev Food Sci Food Safe

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Tree nuts are important economic crops and are consumed as healthy snacks worldwide. In recent years, the increasing needs for more efficient and effective postharvest processing technologies have been driven by the growing production, higher quality standards, stricter food safety requirements, development of new harvesting methods, and demand to achieve energy saving and carbon neutralization. Among all, the technologies related to drying, disinfection, and disinfestation and downstream processes, such as blanching, kernel peeling, and roasting, are the most important processes influencing the quality and safety of the products. These processes make up the largest contribution to the energy consumptions and environmental impacts stemming from tree nut production. Although many studies have been conducted to improve the processing efficiency and sustainability, and preserve the product quality and safety, information from these studies is fragmented and a centralized review highlighting the important technology advancements of postharvest processing of tree nuts would benefit the industry. In this comprehensive review, almonds, walnuts, and pistachios are selected as the representative crops of tree nuts. Current statuses, recent advances, and ongoing challenges in the scientific research as well as in the industrial processing practices of these tree nuts are summarized. Some new perspectives and applications of tree nut processing waste and by‐products (such as the hulls and shells) are also discussed. In addition, future trends and research needs are highlighted. The material presented here will help both stakeholders and scientists to better understand postharvest tree nut processing and provide technological recommendations to improve the efficiency and sustainability, product quality and safety, and competitiveness of the industry.

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Influence of radio frequency treatment on in-shell walnut quality and Staphylococcus aureus ATCC 25923 survival

Cited by 41 publications

References 40 publications

Temperature and Moisture Dependent Dielectric and Thermal Properties of Walnut Components Associated with Radio Frequency and Microwave Pasteurization

Temperature and Moisture Dependent Dielectric and Thermal Properties of Walnut Components Associated with Radio Frequency and Microwave Pasteurization

Effect of Physical Structures of Food Matrices on Heat Resistance of Enterococcus faecium NRRL-2356 in Wheat Kernels, Flour and Dough

Postharvest processing of tree nuts: Current status and future prospects—A comprehensive review

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