Rohan V. Tikekar
· Acting Chair, Professor and Extension Specialist, Co-Program Director Fermentation ScienceVerifiedUniversity of Maryland, College Park · Nutrition and Food Studies
Active 2008–2026
About
Rohan V. Tikekar is a Professor and Extension Specialist in the Department of Nutrition & Food Science at the University of Maryland. He holds a Ph.D. in Food Science from Pennsylvania State University, an M.S. in Food Science from Rutgers University, and a B.Tech. in Food Technology and Engineering from the Institute of Chemical Technology. His research focuses on the development of novel processing technologies and ingredients to enhance food safety and quality. He investigates non-thermal food processing methods such as ultraviolet light and cold plasma, aiming to understand their effects on enzyme activity, contaminant reduction, and food texture. Additionally, he develops innovative photochemical processes for microbial inactivation in fresh produce and explores ingredient interactions during food processing to improve food stability and bioactive compound delivery. His work also includes understanding redox reactions in foods and their impact on food quality, contributing to advancements in food preservation and safety.
Research topics
- Biology
- Chemistry
- Food science
- Biophysics
- Biochemistry
- Biotechnology
- Organic chemistry
Selected publications
Validation of Sanitizer Concentration to Reduce Cross‐Contamination Risk During Washing of Apples
Journal of Food Process Engineering · 2026-02-01
articleOpen accessSenior authorCorrespondingABSTRACT The presence of elevated chemical oxygen demand (COD) during apple washing can negatively affect the effectiveness of sanitizers. Here, we evaluated the effectiveness of 80 ppm sodium hypochlorite (NaOCl) and 80 ppm peracetic acid (PAA) to control and prevent cross‐contamination of Escherichia coli TVS353 on freshly harvested Pink Lady apples ( Malus domestica “Cripps Pink”). One inoculated apple was washed for 2 min in a simulated dump tank wash (SDTW) with 14 uninoculated apples under low (500 mg/L) or high (3000 mg/L) COD conditions. Bacterial enumeration was performed on uninoculated washed apples, inoculated washed apples, and the wash water using a modified most probable number (MPN) method. Results showed significantly higher levels of E. coli TVS353 detected at both low and high COD in the absence of sanitizer (2.3 ± 0.3 and 1.2 ± 0.6 log MPN/apple) compared to NaOCl (0.2 ± 0.0 and 0.3 ± 0.0 log MPN/apple) and PAA treatments (0.2 ± 0.0 and 0.2 ± 0.0 log MPN/apple). PAA was more effective than NaOCl in reducing E. coli on apples, achieving a 5.3–6.0 log reduction compared to NaOCl's 2.9–3.7 log reduction ( p < 0.05). NaOCl's efficacy was negatively impacted by high COD levels, while PAA remained effective. In the absence of sanitizer, substantial cross‐contamination and E. coli persistence in wash water were observed. These findings suggest that applying sanitizer treatment during apple washing is more effective in reducing and preventing the spread of microbes to clean apples and wash water compared to washing with water alone.
Journal of Food Science · 2025-08-01 · 1 citations
articleOpen accessSenior authorCorrespondingABSTRACT Monitoring chemical oxygen demand (COD) during washing of fresh produce is critical to maintaining the antimicrobial efficacy of sanitizers. However, traditional COD analysis is time‐consuming (2–3 h) and costly. Since sugars released from fresh produce contribute to the overall COD, we investigated whether sugar estimation using the colorimetric sulfuric acid‐UV spectrometry method (SA‐UV method) can be a rapid, low‐cost, and field‐deployable method to predict the COD. The method relies on measurement of furfurals (absorbance at 315 nm, A 315 ) formed by sulfuric acid‐induced oxidation of sugars (∼5 min). The correlation between A 315 and measured COD was assessed using the coefficient of determination ( R 2 ) for a linear regression model. A linear prediction model was subsequently developed. We first demonstrated this method with glucose, fructose, and sucrose (0–100 mg/L) solutions. Actual produce (grape, cantaloupe, and pineapple) wash water samples (> 15 samples per commodity) from a facility were then tested to validate this method. Strong positive associations were observed between A 350 versus measured COD in all three sugar solutions ( R 2 > 0.91) as well as for grape ( R 2 = 0.82) and cantaloupe ( R 2 = 0.85) wash samples; while a relatively weaker correlation was observed for pineapple ( R 2 = 0.62). Similar trends were observed between the measured and predicted COD of all three sugar solutions ( R 2 > 0.95) and produce commodities (grape: R 2 = 0.82; cantaloupe: R 2 = 0.87; pineapple: R 2 = 0.65). Compared to turbidity measurements ( R 2 range 0.17–0.59), this method was more accurate ( R 2 range 0.65–0.82) as a predictor of COD. Practical Applications It is critical to monitor chemical oxygen demand (COD) levels in fresh produce wash water because elevated levels are associated with decreased antimicrobial efficacy of applied sanitizing agents. However, traditional COD measurements are time‐consuming (2–3 h), which creates a burden for wash operations, especially under extreme wash water conditions (high COD). The results from this study offer an alternative approach for estimating the COD present in wash water and can be useful for produce wash operations because of the minimal time required, low cost of reagents and supplies, and minimal exposure to toxic chemicals.
Journal of Food Science · 2025-02-01 · 2 citations
articleOpen accessSenior authorCorrespondingThe oxidative species generated by cold atmospheric plasma (CAP) treatment can impact the plant stress response system. We hypothesized that this response is not limited to the site of CAP application and it is transmitted through the plant. The resulting stress response can influence the plant microbiome on the intact plant. These hypotheses were tested by the application of CAP to live sweet basil (Ocimum basilicum var. Kiera). A single upper leaf of the plant underwent a 60 s CAP treatment at three different wattage intensity levels. Reactive oxygen species (ROS) generation in directly treated leaves and leaves in the vicinity of the treatment site (i.e., one, two, or three nodes away) was measured using the fluorescein degradation assay (ex/em: 485/525). Leaves directly exposed to CAP showed a marked increase in ROS production. Interestingly, basil leaves not directly treated by CAP also showed a significant (p < 0.05) increase in ROS generation compared to untreated control, extending to the two nearest nodes from the treatment site in all plants tested. The leaf microbiomes were evaluated using 16S rRNA gene sequencing. CAP appeared to drive restructuring of the leaf microbiota profiles, despite maintaining a similar α-diversity. CAP treatment intensity led to significant differences (p < 0.05) in the relative abundances of a variety of dominant bacterial families (e.g., Psuedomonadaceae and Streptomycetaceae) and phyla, and the effects on certain taxa were dependent on leaf distance from the treatment site. CAP's ability to restructure plant microbiota may have applications to improve produce microbial safety and shelf-life. PRACTICAL APPLICATION: Cold atmospheric plasma induces a stress response in a living plant beyond the site of application. This response includes an increase in the production of reactive oxygen species that can trigger pathways to enhance the production of phytochemicals. CAP treatment also alters the microbial community profile, possibly through plant stress response. Results from this study can be useful in developing CAP treatment of intact plant for improved growth, production of health-benefiting phytochemicals, and managing its microbiota.
PLoS ONE · 2025-11-03 · 1 citations
articleOpen accessSenior authorCorrespondingCopper is essential for all living organisms, but becomes toxic when present in excess. Biological systems have evolved mechanisms to keep organisms in copper homeostasis. Studies have shown that Salmonella can acquire mobile genetic elements that provide enhanced tolerance to stressed environments, such as the Copper Homeostasis and Silver Resistance Island (CHASRI), which has become more prevalent in certain serovars that are exposed to higher levels of copper. In this study, whole genome sequence data available from NCBI Pathogen Detection was used to determine the incidence of the CHASRI is in Salmonella enterica isolates. The results show that the CHASRI is present in a wider range of serovars than previously known and can be found in isolates from different food sources, including nuts, spices, and produce. Salmonella Genomic Island-4 (SGI-4) was previously described as the primary mobile element through which the CHASRI was transferred to Salmonella; however, results from this comparative study of closed reference genomes identified additional integrations of the CHASRI as both a singular mobile element and as a component of an SGI-4 variant.
Journal of Food Science · 2025-01-01 · 4 citations
articleOpen accessSenior authorCorrespondingWe evaluated the antimicrobial performance of sodium hypochlorite (NaOCl) and peracetic acid (PAA) during washing of baby spinach in water of varying levels of organic load, as measured by its chemical oxygen demand (COD). Escherichia coli TVS353 was spot inoculated onto one unwashed leaf. Sanitizers were added into water with preadjusted COD (300 or 2500 ppm) to achieve concentrations from 20 to 80 ppm. One inoculated leaf was washed with nine uninoculated leaves in 500 mL water (n = 6). Bacterial load on inoculated leaves was lowered by sanitizers in a dose-dependent manner (p < 0.05) and the lowest bacterial survivor levels were observed at 80 ppm with 2.7 ± 1.2 and 5.1 ± 0.5 Log MPN/leaf for PAA and NaOCl, respectively, at low CODs. PAA was more effective in reducing bacterial load from the inoculated leaf than NaOCl at high CODs (p < 0.05), with 2.9 ± 2.8 and 5.3 ± 0.8 Log MPN/leaf survivors for PAA and NaOCl, respectively. At 80 ppm sanitizer levels, the bacteria was not detected in wash water at any condition but was detected at 20 and 40 ppm at high CODs. The lowest levels of bacteria transferred to uninoculated leaves were observed at 80 ppm sanitizer, at 0.3 ± 0.2 and 0.2 ± 0.1 Log MPN/leaf for PAA and 1.1 ± 1.0 and 0.3 ± 0.3 Log MPN/leaf for NaOCl at low and high CODs, respectively. The log percentage of bacteria transferred ranged from -1.1 at 0 ppm to over -4.5 at 80 ppm, highlighting a reduction in cross-contamination by the sanitizers. PRACTICAL APPLICATION: This study provides effective data on sanitizer usage to fresh produce industry for ensuring food safety during washing of produce. It evaluated the sanitizer effect in a broad range of scenarios including various sanitizer concentrations, and wash water with low and high organic load that is common when recirculating wash water. The results also revealed the differences in two common sanitizers (PAA and NaOCl) in terms of their effectiveness.
Journal of Food Safety · 2025-04-30 · 1 citations
articleOpen accessSenior authorCorrespondingABSTRACT Addition of antimicrobials to water used for irrigation of fresh produce is recommended to reduce microbial food safety risks. However, there remains a need to validate the efficacy of antimicrobials in irrigation water using the microbial strains and methods recommended by the Environmental Protection Agency (EPA). We evaluated the antimicrobial performance of calcium hypochlorite (Ca(ClO) 2 ) (2–4 and 10–12 ppm) and peroxyacetic acid (PAA) (6 and 10 ppm) individually in ground and surface agricultural production water in Maryland using the EPA recommended method (No. 94151PA7). Both water samples were slightly alkaline (pH 8.13 and 8.01, respectively) and low in turbidity (0.65 and 4.82 NTU, respectively). A total of 1 mL of EPA‐recommended Escherichia coli or Salmonella enterica cocktail (approximately 9.0–9.7 log CFU/mL) was inoculated in 98 mL of irrigation water in three flasks and equilibrated at 12°C or 32°C, resulting in 7.0–7.7 log CFU/mL bacterial levels. One milliliter of sanitizer solution (Ca(ClO) 2 or PAA) was added into the flask followed by mixing for 15 s. At 5 and 10 min, samples were transferred into phosphate buffer saline containing 0.28 g/mL sodium metabisulfite, serially diluted, and plated on quadruplicated TSA‐Rifampicin plates for enumeration. Both low and high levels of Ca(ClO) 2 and PAA solutions inactivated over 4.5 log CFU/mL of E. coli and Salmonella cocktails within 5 min at either water temperature, which exceeded the 3‐log threshold required by the EPA. Total bacterial inactivation at 10 min exceeded 5 log CFU/mL. The results demonstrated that, in slightly alkaline irrigation water, adequate sanitizing efficacy was achieved with 2–4 ppm of Ca(ClO) 2 and 6 ppm of PAA.
Journal of Food Science · 2024-01-15 · 1 citations
articleOpen accessSenior authorCorrespondingSalmonella has been associated with numerous outbreaks from contaminated food products, including emulsions. Emulsions are influenced by emulsifier type and oil presence, which can have varying degrees of stress or protection on bacteria. Although our previous research has shown that emulsifier solutions, rather than emulsions, provide a protective effect on Salmonella typhimurium after thermal treatment, the underlying mechanism remains unclear. This study selected S. typhimurium as the model microorganism and utilized the same emulsifiers (Tween 20, Tween 80, Triton X-100) to create emulsifier solutions and emulsions with the same oil fraction (60% (v/v)) to examine their effect on the expression of nine selected genes (rpoE, rpoH, otsB, proV, fadA, fabA, dnaK, ibpA, ompC) associated with stress response. Specifically, the study observed variations in gene expression under normal and thermal stress at 55°C. After 20-h incubation, Triton X-100 emulsion caused an upregulation of stress-related genes, rpoE, otsB, and fabA, suggesting stressful environment. After thermal treatment, S. typhimurium in Triton X-100 solution showed a longer 5-log reduction time with increased proV and decreased fabA and ompC expression, suggesting enhanced thermal protection compared to its emulsion. Conversely, Tween 80 solution increased fabA and ompC expression, indicating greater membrane fluidity and passive diffusion, potentially reducing thermal resistance. However, according to the upregulation of ibpA, this effect was likely mitigated by the overproduction of heat shock proteins. Notably, Triton X-100 environments exhibited the most significant gene expression changes after heat treatment, whereas Tween 80 without oil was the most inhospitable for bacterial survival. These findings inform bacterial responses under various conditions, aiding food safety strategies.
Journal of Food Safety · 2024-05-02 · 3 citations
articleOpen accessSenior authorCorrespondingAbstract Low level of rifampicin‐resistant E. coli is frequently used in food safety research as a model microorganism and is typically enumerated using traditional Most Probable Number (MPN) method. To simplify the process, we developed and validated a modified MPN method based on lactose peptone broth (LPB) containing rifampicin and bromocresol purple, the broth changes to a yellow color due to pH shifts induced by lactose fermentation from E. coli . E. coli TVS353 were prepared in following suspensions including healthy cells, injured cells, competitive bacteria with or without rifampicin resistance, and unknown natural microflora. E. coli TVS353 was quantified by traditional MPN method and our improved method. At a predicted level of 1 log CFU/mL, there was no significant difference in the MPN index of LPBR compared with TSB and TSBR in these suspensions ( p > 0.05). Confirmation results generated from this new color change MPN method were analogous to traditional MPN methods.
Food Science & Nutrition · 2024-11-04
articleOpen accessSenior authorCorrespondingABSTRACT Molecular characteristics of emulsifiers such as their molecular weight (MW) and surface charge, not only affect the stability of the emulsion but also can have an impact on its capacity to either inhibit or promote microbial proliferation. These characteristics can affect the behavior of pathogens such as Salmonella Typhimurium in emulsion systems. The growth and thermal resistance of S . Typhimurium were monitored at different oil content levels (20%, 40%, and 60%) in emulsions stabilized by three whey protein‐based emulsifiers: whey protein isolate (WPI), whey protein hydrolysate (WPH), and a modified WPI with an alteration of charge (WPI + ). Our study revealed that emulsifier itself with different MW and surface charge had no effect on bacterial growth and inactivation without oil inclusion ( p > 0.05). However, it was found that higher bacterial growth rate at 60% oil content emulsion stabilized with WPI + (0.65 ± 0.03 log CFU/h) than WPI (0.19 ± 0.04 log CFU/h), which showed the charge of emulsifiers has different effects on microbial dynamics in oil‐in‐water emulsion. Interestingly, WPI + in emulsions also seemed to convey protection against thermal inactivation of bacteria. These data describe a complex interrelationship between the physicochemical characteristics of the emulsifier and its interacting nature with bacterial cells. They throw even more light on the insight about the importance of a strategic approach toward emulsifier selection in food formulations. This is crucial for the food safety and stability of products.
Innovative Food Science & Emerging Technologies · 2024-01-14 · 5 citations
articleSenior authorCorresponding
Frequent coauthors
- 36 shared
Nitin Nitin
- 13 shared
Erick F. de Oliveira
Universidade Federal do Ceará
- 12 shared
Robert L. Buchanan
Center for Food Safety and Applied Nutrition
- 12 shared
Qiao Ding
- 11 shared
Luis J. Bastarrachea
Utah State University
- 10 shared
Yuanjie Pan
Xuzhou Medical College
- 8 shared
Chongtao Ge
- 6 shared
Zhujun Gao
University of Maryland, College Park
Education
- 2010
PhD, Food Science
Pennsylvania State University
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