Integrated assessment of agricultural and processing-related chemical hazards across the food chain: glyphosate occurrence and lipid changes in ready-to-eat corn-based foods

1 Introduction

Chemical and microbiological contamination of foods represents a major concern for food safety, particularly in collective consumption environments where food is prepared repeatedly and under variable sanitary control. Chronic dietary exposure to chemical residues, even at low concentrations, may pose cumulative health risks, especially when contaminants are present in staple foods consumed daily (Suvorov and Stancu, 2021). Prepared foods are particularly relevant for food safety surveillance as a component of food security because they may contain chemical hazards originating at different stages of the food chain, including agricultural residues and compounds generated during thermal processing (Bejarano Roncancio and Suárez Latorre, 2015; Zhang et al., 2020). Although these hazards arise through independent processes, they ultimately coexist within the same food matrix and contribute to overall dietary chemical exposure.

Food security depends not only on food availability and access but also on the safety and quality of foods reaching consumers. Within the conceptual framework proposed by the Food and Agriculture Organization of the United Nations (FAO), food utilization encompasses the safe consumption of food as a prerequisite for achieving food security (FAO, 2006). Consequently, this dimension may be compromised by chemical contaminants originating at different stages of the food chain, particularly in institutional food environments where ready-to-eat foods constitute a substantial part of the diet.

In Mexico, corn-based foods such as tortillas and tortilla chips constitute a fundamental component of the daily diet and are widely consumed in institutional settings, including university cafeterias and food stalls. Given the high per capita consumption of corn-based food products in Mexico (González-Ortega et al., 2017; Solís-Martínez et al., 2025), even low levels of contaminants may result in continuous exposure. Within the university environment, specific dietary patterns reinforce this risk; for instance, “chilaquiles” (fried tortilla chips simmered in sauce) are among the most frequently consumed dishes in campus cafeterias, representing a staple of the institutional diet (Ascencio-López et al., 2025). Furthermore, tortillas play a significant role in daily university nutrition as the primary vehicle for traditional products like “tacos.” Due to their low cost and high availability, these products represent a primary food source for college students, a population characterized by frequent consumption of ready-to-eat foods and limited nutritional oversight (Chandrika et al., 2021).

Glyphosate (N-(Phosphonomethyl) glycine; molecular formula C₃H₈NO₅P; CAS No. 1071-83-6), with a molar mass of 169.07 g/mol, is the most widely used herbicide worldwide and has raised increasing concern due to its persistence in food products and potential long-term health effects (Martins-Gomes et al., 2022; Klátyik et al., 2023; González-Cruz et al., 2025). Although its mechanism of action targets shikimic acid pathway in plants (Louie et al., 2021; Vicini et al., 2021), glyphosate residues have been frequently detected in corn and processed foods, raising concerns about chronic dietary exposure (González-Cruz et al., 2025). This exposure has been associated with systemic toxicity, including neurodegenerative, endocrine, and multi-organ effects (Peillex and Pelletier, 2020; Ignácio et al., 2024; Nunes et al., 2024; Hu et al., 2025; Stone et al., 2025). In 2015, the International Agency for Research on Cancer (IARC) classified glyphosate as “probably carcinogenic to humans” (IARC and WHO, 2015).

Although regulatory agencies have established acceptable exposure limits for glyphosate, concerns regarding chronic dietary intake persist. In Mexico, the acceptable daily intake (ADI) is 0.3 mg kg⁻¹ day⁻¹ and the maximum residue limit (MRL) for corn is 0.1 mg kg⁻¹ (COFEPRIS, 2009), which is more stringent than the Codex Alimentarius MRL of 5 mg kg^-1 (Codex Alimentarius Commission, 2006). This regulatory framework reflects the national policy aimed at gradually replacing glyphosate in staple crops. However, herbicide continues to be widely used because economically and agronomically viable alternatives remain limited. Since no specific MRL has been established for processed corn products, the MRL for corn grain was considered only as a regulatory reference point for contextual comparison with the concentrations measured in tortillas and tortilla chips, rather than as a product-specific compliance limit.

Additionally, frying is one of the most common cooking practices in institutional food services. Repeated thermal exposure of vegetable oils promotes oxidative degradation, reducing lipid unsaturation and generating oxidation products than may compromise both nutritional quality and food safety (FAO, 2006; Montenegro-Bonilla et al., 2023). Consequently, ready-to-eat foods may contain chemical hazards originating from different stages of the food chain, including agricultural residues remaining from crop production and chemical changes generated during food preparation. Although these processes arise independently, they converge within the same food matrix consumed by the population, supporting an integrated food safety perspective.

Despite the public health relevance of this integrated perspective, the analysis of pesticide exposure in institutional food services has also highlighted data gaps concerning processed and ultra-processed foods, as well as limitations in the availability of maximum residue limits and food-specific residue data (da Silva et al., 2024). This underscores the necessity for further research to assess agricultural chemical residues in conjunction with processing-related changes in ready-to-eat foods consumed under real food-service conditions.

Furthermore, although Mexico is implementing policies aimed at the gradual substitution of glyphosate, the herbicide continues to be widely used because effective alternatives capable of maintaining agricultural productivity remain limited. Consequently, residues may still reach processed foods that are subsequently subjected to thermal preparation.

Therefore, this study aimed to provide an integrated assessment of chemical hazards across the food chain by screening glyphosate occurrence as an agricultural contaminant together with evaluating processing-related changes in lipid saturation in tortillas and tortilla chips consumed within a Mexican university campus. Rather than investigating mechanistic interactions between glyphosate and processing-derived compounds, the study evaluates complementary sources of chemical risk that coexist within the same ready-to-eat food matrix, providing a more realistic representation of dietary exposure in institutional food environments.

2 Materials and methods

2.1 Materials and samples

All chemical reagents and solvents used in this study were obtained from Sigma-Aldrich, Inc. (Toluca, Mexico), and J.T. Baker (Mexico City, Mexico). Acetonitrile and water used for sample extraction and mobile phase preparation were of High performance liquid chromatography (HPLC) or liquid chromatography–mass spectrometry (LC–MS) grade, while all other chemicals and reagents were of analytical grade and used without further purification. Glyphosate standard (purity ≥98%) was obtained from Sigma-Aldrich, Inc. (Toluca, Mexico). Quantification was performed using an external calibration curve prepared from a commercial glyphosate standard with known concentration. No internal standard was used in the analytical procedure.

A total of 32 samples were collected for this study, comprising 20 corn-based foods (10 tortillas and 10 tortilla chips) and 12 vegetable oil samples (6 paired samples collected before and after frying). Samples were randomly collected from cafeterias and food stalls that represent the main food sources for students at Ciudad Universitaria of the Benemérita Universidad Autónoma de Puebla, Mexico, between June 10 and 12, 2024. The samples were intended for preliminary screening of glyphosate occurrence and processing-related lipid changes in this specific university food environment.

For each tortilla sample, two standard units (approximately 55 g) were collected. Tortilla chip samples consisted of 20 units per sample, (35–40 g). Food samples were placed clean, labeled polyethylene bags and transported under refrigeration to the laboratory for analysis. Vegetable oil samples were collected directly from frying equipment before and after use. Each oil sample was transferred to amber glass bottles, protected from light with aluminum foil, sealed, labeled, and transported to the laboratory for analysis.

2.2 Analytical strategy and experimental design

The analytical strategy was designed considering the characteristics of processed corn-based foods, which typically contain lipid fractions derived from frying processes that may interfere with chromatographic detection. High-performance liquid chromatography with diode-array detection (HPLC-DAD) was employed as a screening approach to evaluate glyphosate occurrence in processed corn-based foods. No derivatization step was applied prior to chromatographic analysis. Glyphosate occurrence was evaluated by direct HPLC-DAD analysis under the chromatographic conditions described below. Oil degradation was evaluated by Fourier-transform infrared spectroscopy (FTIR) through estimation of iodine value (IV). Each analytical method was independently validated according to its respective performance parameters.

2.3 Screening of glyphosate occurrence using HPLC-DAD

2.3.1 Sample preparation

Sample treatment followed the methodology described by Cano García et al. (2023), with specific adaptations for processed corn-based matrices. Initially, 15 g of each homogenized sample was weighed and transferred into cellulose extraction cartridges. The procedure included a pre-treatment step to address the high fat content in tortilla chips. Samples underwent Soxhlet extraction using 180 mL of hexane for five reflux cycles under controlled conditions. Hexane removed lipophilic components and frying oils from the matrix. This lipid removal reduces matrix interference and potential interference (Cherta et al., 2013; Łozowicka et al., 2014). Following extraction, the solvent was removed using a rotary evaporator (Sev, model A402-2). Samples were reconstituted in 15 mL of distilled water. This aqueous recovery is highly effective for glyphosate due to its high polarity and water solubility, an approach previously validated in cereal matrices (Cano García et al., 2023). Despite glyphosate’s polar nature, this protocol ensures adequate recovery and reproducibility. Finally, the solution was filtered through a 0.20 μm nylon syringe filter (Agilent Technologies, Captiva, Santa Clara, CA, USA) prior to chromatographic analysis.

2.3.2 Method validation

Glyphosate analysis was performed using an Agilent 1260 HPLC system equipped with a diode array detector (HPLC-DAD) (Santa Clara, CA, USA). Separation was achieved with a ZORBAX Eclipse Plus C18 column (4.6 × 150 mm, 5 µm). The mobile phase consisted of acetonitrile and water (60:40 v/v) at a flow rate of 0.5 mL min⁻¹. The injection volume was 20 μL, and detection was carried out at 234 nm. Data acquisition and analysis were performed using OpenLab CDS software (version 2.8, Agilent Technologies). Glyphosate stock solutions were prepared from the analytical standard (purity ≥98%) obtained from Sigma-Aldrich, Inc. These solutions were used to fortify a blank tortilla matrix with no detectable glyphosate signal under the analytical conditions. A matrix-matched external calibration curve was prepared at nine concentration levels ranging from 0 to 2.00 mg L⁻¹. The analytical performance parameters obtained from the calibration and fortification experiments are summarized in Table 1.

Table 1. Analytical performance of the HPLC-DAD screening procedure for glyphosate.

*RSD, Relative standard deviation. Intra-day RSD. Values correspond to 0.20, 0.40, and 0.60 mg L⁻¹, respectively.

Precision was evaluated using matrix fortified at three concentration levels (0.20, 0.40, and 0.60 mg L⁻¹), with three replicates per concentration level over three consecutive days. Recovery was also evaluated using the fortified matrix. No internal standard was used, and matrix effects were not independently quantified by comparison of solvent- and matrix-based calibration slopes.

For screening purposes, peak assignment was based primarily on the retention time established with the glyphosate calibration standard (RT = 1.658 min). DAD spectral information was not used as an independent confirmation criterion. Because glyphosate exhibited early elution under the selected reversed-phase conditions, retention-time matching alone was not considered sufficient for definitive identification. Accordingly, the procedure was applied as a screening approach, and confirmation by liquid chromatography–tandem mass spectrometry (LC–MS/MS) or another suitably selective analytical method would be required for definitive identification and quantitative confirmation. The results were compared with the maximum residue limit (MRL) established for corn in Mexico (0.1 mg kg⁻¹) (COFEPRIS, 2009), and the Codex Alimentarius MRL (5 mg kg⁻¹) (FAO/WHO, 2024).

2.3.3 Risk assessment

Dietary exposure to glyphosate was calculated using the Estimated Daily Intake (EDI) and Hazard Quotient (HQ) models.

The EDI of glyphosate was calculated in Equation 1:

EDI = C × IR BW (1)

where C is the highest screening-level glyphosate concentration detected in the analyzed food samples (mg kg⁻¹), IR is the daily intake rate of corn-based food (kg day⁻¹), and BW is the average body weight (kg). A daily intake rate of 0.5 kg of corn-based foods was used, based on the average per capita consumption reported for Mexico by González-Ortega et al. (2017), and the BW was 58 kg for women and 65 kg for men (Forbe et al., 2008). For the conservative exposure scenario, the highest screening-level glyphosate concentration detected across the analyzed food samples (1.994 mg kg⁻¹ bw day⁻¹) was used. Thus, the assessment represents an upper-bound screening scenario in which the maximum observed concentration is applied to the assumed daily intake of corn-based foods.

The HQ values were calculated using Equation 2:

HQ = EDI ADI (2)

where ADI is the acceptable daily intake for glyphosate (0.3 mg kg⁻¹ bw day⁻¹), according to (COFEPRIS, 2009). An HQ value below 1 indicates estimated exposure below this reference value under the assumptions used but does not imply absolute safety. As EDI was expressed on a daily basis, exposure frequency (EF) and averaging time (AT) were not included separately because EDI was expressed on a daily basis. The conservative scenario used the highest screening-level concentration and the assumed daily intake of corn-based foods.

For example, for women (58 kg body weight), using C = 1.994 mg kg⁻¹ and IR = 0.5 kg day⁻¹:

EDI = 1.994 mg kg − 1 × 0.5 kg day − 1 58 bw kg = 0.01719 mg kg − 1 bw day − 1

The corresponding HQ was calculated as:

HQ = 0.01719 mg kg − 1 bw day − 1 0.3 mg kg − 1 bw day − 1 = 0.0573

The exposure assessment was not performed as separate consumption scenarios for tortillas and tortilla chips, nor as a combined consumption model based on the actual consumption proportions of both products. Instead, a conservative upper-bound screening scenario was constructed using the highest screening-level concentration detected across the analyzed food samples (1.994 mg kg⁻¹) and the reported average daily intake of 0.5 kg of corn-based foods.

2.4 FT-IR spectroscopy analysis of oils

FT-IR spectra of vegetable oil samples were recorded using a Bruker ALPHA II Platinum spectrophotometer. Spectra were acquired over the interval of 4,000–400 cm⁻¹, with a resolution of 4 cm⁻¹, averaging 32 scans per measurement.

The iodine value (IV), as an indicator of unsaturation degree, was estimated according to Guillén and Cabo (1998) using the absorbance ratio between the olefinic bonds band at 3,007 cm⁻¹ and the aliphatic groups at 2,824 cm⁻¹, (x = A₃₀₀₇/A₂₈₂₄). The IV was calculated in Equation 3:

IV = 4.5 × 751.4 x (3)

where IV represents the iodine value, and x is the absorbance ratio. The coefficients a = 4.5 and b = 751.4 were determined via simple linear regression, with a coefficient of determination R² = 0.99. Differences between paired oil samples collected before and after frying were evaluated using a paired t-test, with statistical significance set at p < 0.05. The normality of the paired differences was assessed using the Shapiro–Wilk test. Because the analysis involved paired observations, homogeneity of variance between groups was not assumed. Effect size and 95% confidence intervals were calculated to complement the p-value. FT-IR analysis was applied as a rapid, non-destructive screening approach to evaluate the degree of lipid unsaturation associated with rancidity and oxidation through the estimation of IV (Castorena-García et al., 2011). This analytical approach was not intended for the identification of specific oxidation or degradation products, but rather to function for assessing structural changes in fatty acids associated with thermal processing.

3 Results and discussion

The analytical procedure used for screening glyphosate occurrence in processed corn-based foods demonstrated adequate analytical performance under the conditions of this study. The matrix-matched calibration curve was linear over the concentration range of 0–2.00 mg L⁻¹ (R² = 0.9994), as presented in Figure 1, with a limit of detection (LOD) of 0.06 mg L⁻¹ and a limit of quantification (LOQ) of 0.19 mg L⁻¹. The concentrations reported below should therefore be interpreted as screening-level estimates obtained under the analytical conditions described above (Figure 2). Repeatability and reproducibility, expressed as relative standard deviation (%RSD), were evaluated at three matrix-fortification levels (0.20, 0.40, and 0.60 mg L⁻¹) in triplicate over three consecutive days. Intra-day precision values were 3.14%, 1.06%, and 1.06% RSD, respectively, whereas inter-day precision values were 3.89%, 1.15%, and 1.27% RSD, respectively. Recovery ranged from 98.71 to 101.27% (Table 2). These results indicate consistent analytical performance under the experimental conditions used.

Table 2. Performance characteristics of the HPLC-DAD screening method.

RSD, relative standard deviation.

Screening-level glyphosate signals were detected in 8/10 tortilla samples (80%) and 10/10 tortilla chip samples (100%), corresponding to 18 of the 20 samples analyzed (90% overall). Screening-level concentrations in tortillas ranged from 0.107 to 1.994 mg kg⁻¹, while tortilla chips showed concentrations between 0.170 and 1.373 mg kg⁻¹ (Table 3). Because the study design did not include controlled frying experiments using the same starting material, the comparison between tortillas and tortilla chips was observational and does not allow the effect of frying on glyphosate concentrations to be isolated. All detected concentrations remained below the Codex Alimentarius MRL for corn grain (5 mg kg⁻¹). However, most analyzed samples (90%) showed screening-level concentrations above 0.1 mg kg⁻¹, the Mexican MRL established for corn (COFEPRIS, 2009), which was used here as a regulatory reference point. Therefore, in the absence of a specific MRL for tortillas and tortilla chips, these comparisons should be considered within a broader regulatory context rather than as a direct determination of compliance for the processed products analyzed. Among all analyzed samples, the highest screening-level concentration was observed in tortillas (1.994 mg kg⁻¹), whereas the highest concentration in tortilla chips was 1.373 mg kg⁻¹ (Figure 3). This discrepancy underscores differences between national and international regulatory criteria and highlights the need for clearer residue standards in processed corn-based foods.

Table 3. Glyphosate concentration (mg kg⁻¹) from tortillas and tortilla chips samples collected in cafeterias located within Ciudad Universitaria of Benemérita Universidad Autónoma de Puebla, Mexico.

ND, non detected.

Due to its strong affinity for water and high hydrophilicity, glyphosate exhibits limited retention under conventional reversed-phase C18 chromatographic conditions. The observed retention time (RT = 1.658 min) occurred at an early point in the chromatographic run, increasing the potential for coelution with polar matrix components. The Soxhlet pretreatment was incorporated to remove lipophilic constituents and reduce matrix complexity prior to chromatographic analysis. However, because matrix effects were not independently quantified, their complete exclusion cannot be demonstrated. The matrix-matched calibration, recovery, and precision results support the consistency of the analytical response under the experimental conditions used. Nevertheless, given the early elution of glyphosate and the absence of confirmatory analysis by LC–MS/MS, the procedure was applied as a screening method, intended as an accessible analytical tool for assessing the presence of glyphosate, particularly in laboratories without access to LC–MS/MS instrumentation, rather than as a confirmatory method.

Compared with studies from Europe and North America, where glyphosate levels in processed foods are generally below MRLs (Xu et al., 2019; Zoller et al., 2020), the concentrations observed here indicate significant regional variability. This pattern likely reflects differences in agricultural practices, regulatory enforcement, and supply chains. In Europe, glyphosate is mainly applied in annual cropping systems for pre-sowing weed control and post-harvest desiccation under relatively standardized management conditions (Antier et al., 2020). In contrast, glyphosate use in Mexico and Latin America is more heterogeneous, influenced by diverse agronomic and socio-economic conditions (González-Ortega et al., 2017; Monroy-Sais et al., 2022).

In Mexico, fewer studies have evaluated glyphosate occurrence in processed corn-based food than in Europe or North America. Nevertheless, previous surveys have documented glyphosate in commercially available corn products, including tortillas, tortilla chips, corn flour, breakfast cereals, and snack products, suggesting that agricultural residues may persist throughout processing and distribution before reaching consumers (González-Ortega et al., 2017). The concentrations observed in the present study fall within the range reported for processed corn-derived foods in Mexico, although direct comparisons should be interpreted cautiously because of differences in sampling strategies, analytical methodologies, and food matrices.

According to the Mexican regulatory framework (SENASICA, 2020), glyphosate in corn is recommended for pre-planting (chemical fallow) or early post-emergence (prior to the V4–V5 stage). In practice, however, herbicide application strategies vary considerably according to production systems, farm size, mechanization, and local agronomic conditions, and glyphosate is frequently used together with other herbicides such as 2,4-D and paraquat in conventional corn cultivation (Secretaría de Agricultura y Desarrollo Rural (SADER), 2018; González Ortega and Fuentes Ponce, 2022; Monroy-Sais et al., 2022). Studies conducted in Mexican corn production systems further indicate that the intensity and combination of agrochemical inputs differ among management systems, reflecting the diversity of weed-control practices employed under conventional agriculture (Martínez et al., 2020). Consistent with this scenario, the National Agricultural Survey (INEGI, 2020), approximately 59% of agricultural production units in Mexico reported the use of chemical herbicides, illustrating the continued dependence on herbicide-based weed management in the country (INEGI, 2020). Because the tortillas and tortilla chips analyzed in this study were obtained through market surveillance, whether the corn originated from glyphosate-tolerant genetically modified or conventional production systems could not be verified. Nevertheless, the occurrence of glyphosate detected in these ready-to-eat foods is consistent with agricultural practices reported for corn production in Mexico, where residues originating during crop cultivation may persist into processed foods. This interpretation is supported by previous surveys demonstrating glyphosate occurrence in commercially available corn-derived foods in Mexico, including tortillas, tortilla chips, corn flour, breakfast cereals, and snack products, indicating that agricultural residues may persist throughout food processing and distribution before reaching consumers (González-Ortega et al., 2017).

Mexico has adopted a policy aimed at the gradual substitution of glyphosate based on environmental and public health concerns (González-Moscoso et al., 2023), however, the limited availability of effective alternatives and its cost-effectiveness contribute to its continued use in agricultural practices. Similar variability has been reported across Latin America, where glyphosate is extensively used under diverse agricultural models, ranging from intensive transgenic systems in Argentina to more heterogeneous production systems in other countries (Ramírez-Muñoz et al., 2017). These differences in application practices, together with variability in regulatory enforcement and supply chains, likely contribute to the higher and more heterogeneous glyphosate residue levels observed in processed corn-based foods in Mexico. Although this research is rooted in a specific Mexican regional context, the findings primarily reflect localized dietary exposure shaped by regional production and consumption patterns. Nevertheless, the methodological framework proposed here (integrating agricultural residue analysis with processing-related indicators) is broadly applicable beyond the specific geographical setting. This dual-hazard approach provides a model for evaluating integrated assessment of agricultural and processing-related chemical hazards. Overall, the occurrence of glyphosate in ready-to-eat foods reflects the continuity of agricultural practices along the food chain, whereby herbicide applications performed during crop production may ultimately influence consumer exposure through processed food products. This continuity reinforces the need for food safety assessments that consider agricultural chemical hazards beyond the field and throughout subsequent stages of the food chain.

Dietary exposure was estimated using the highest detected concentrations and average consumption scenarios. The estimated daily intake (EDI) values were 0.01719 mg kg⁻¹ bw day⁻¹ for women and 0.01534 mg kg⁻¹ bw day⁻¹ for men, with corresponding hazard quotient (HQ) values of 0.0573 and 0.0511, respectively. Both HQ values were below 1.0, indicating that the estimated exposure was below the selected ADI under the assumptions of this conservative screening scenario. However, an HQ < 1 should not be interpreted as evidence of complete safety or absence of risk. Nevertheless, the frequent detection of glyphosate and the proportion of samples exceeding the national MRL underscore the necessity for continued monitoring, particularly in populations with high corn-based food intake.

It is noteworthy that tortilla chips showed lower mean glyphosate concentrations (0.366 mg kg⁻¹) compared to fresh tortillas (0.482 mg kg⁻¹). This observation may suggest a potential influence of frying on residue levels. Previous studies have shown that thermal processing can reduce pesticide residues in certain food matrices (Phopin et al., 2022). However, controlled experimental studies would be required to confirm whether thermal degradation, matrix interactions, or processing variability account for the observed differences. Additionally, possible transformation products such as aminomethylphosphonic acid (AMPA) should be considered in future studies (Aslam et al., 2022; Mohy-Ud-Din et al., 2023).

In addition to pesticide residues, ready-to-eat fried foods may also contribute to chemical exposure through processing-related changes. The degradation of frying oils can lead to the formation of secondary oxidation products, which represent an additional source of dietary chemical exposure. Therefore, oil quality was evaluated as a complementary indicator of processing-related chemical hazards within the same food system. FT-IR spectra revealed characteristic absorption bands corresponding to olefinic =C–H at 3,007 cm⁻¹ and aliphatic –C–H₂ stretching at 2,824 cm⁻¹ (Figure 4). The iodine value (IV), calculated from the absorbance ratio, was used as an indicator of unsaturation degree.

The IV decreased after frying across the paired oil samples. The mean paired difference was 5.00 units (95% CI: 1.30–8.71), with a significant difference between pre- and post-frying samples (paired t-test, t(5) = 3.47, p = 0.0178; Cohen's dz = 1.42) (Table 4). This reduction indicates a decrease in the degree of lipid unsaturation and/or structural alteration following thermal processing. Decreases in IV reflect changes in the degree of fatty acid unsaturation, which may influence oxidative stability and nutritional quality. The IV values of several oils were lower than some values described in the literature for fresh soybean, sunflower, and canola oils (Secretaría de Economía, 2005; Neagu et al., 2013; Lafont et al., 2014), suggesting that thermal exposure and repeated use may contribute to changes in oil quality. Although IV reduction does not allow the identification or quantification of specific lipid oxidation products, it provides an indicator of changes in lipid unsaturation associated with frying processes and reflects structural alterations that may influence the chemical quality of ready-to-eat foods. Thermal processing of vegetable oils can generate a wide range of degradation products, including malondialdehyde (MDA), 4-hydroxynonenal (4-HNE), and other reactive aldehydes, as well as total polar compounds, which have been associated with pro-inflammatory responses and oxidative stress (Grootveld et al., 2020; Gharby et al., 2025). However, these compounds were not identified or quantified in the present study; therefore, their occurrence cannot be directly inferred from the observed decrease in IV.

Table 4. Iodine values of six vegetable oils samples collected before and after frying from cafeterias located within Ciudad Universitaria of Benemérita Universidad Autónoma de Puebla, Mexico.

Each post-frying sample was paired with its corresponding pre-frying sample (n = 6 independent pairs).

Values are mean ± SD. Different superscript letters indicate significant differences between pre- and post-frying conditions within each oil sample (p < 0.05). Overall comparison: paired t-test, t(5) = 3.47, p = 0.0178.

The observed decrease in IV indicates changes in lipid unsaturation associated with thermal processing. FTIR spectroscopy has been used to monitor compositional and spectral changes in edible oils during heating and oxidation, supporting its application for the rapid assessment of oil characteristics (Poiana et al., 2022; Zahir et al., 2017). However, the FTIR-derived IV does not distinguish among specific oxidation pathways or directly assess individual oxidation markers, such as lipid hydroperoxides, total polar compounds, or polymerized triglycerides. Therefore, the present findings should be interpreted as a screening-level assessment of changes in lipid unsaturation under frying conditions. Complementary analytical methods would be required to identify and quantify specific oxidation products. These results highlight the relevance of monitoring frying oil quality in institutional food environments.

Although glyphosate residues and processing-induced lipid changes originate through independent mechanisms, both may occur in the same ready-to-eat food matrix. Their joint assessment provides a broader food-safety perspective by considering agricultural chemical residues alongside changes associated with food preparation. This integrated approach does not imply mechanistic interactions between glyphosate and lipid oxidation products; rather, it recognizes that chemical hazards may arise at different stages of the food chain, from crop production to processing and consumption.

Accordingly, ready-to-eat corn-based foods should be regarded as a convergence point for agricultural and processing-related chemical hazards across the food chain. The present findings illustrate how agricultural inputs and technological food preparation practices independently influence the chemical quality of foods that ultimately reach consumers. Therefore, integrating both sources of hazards within the same food safety assessment framework offers a more representative characterization of dietary exposure than evaluating agricultural residues or processing-related changes separately. The findings provides baseline information on glyphosate occurrence and lipid changes in corn-based foods within a university setting, supporting future research and monitoring in other food environments.

This study presents some limitations that should be considered. Glyphosate occurrence was evaluated using HPLC-DAD without confirmatory analysis by LC–MS/MS which may limit analytical selectivity due to the early elution of glyphosate under reversed-phase conditions and the potential for coelution with polar matrix components. Therefore, confirmatory analysis by LC–MS/MS is recommended for trace-level quantification. Nevertheless, the method demonstrated adequate linearity, recovery, and precision, supporting its suitability as a screening approach under the conditions of this study. Additionally, the study focused exclusively on glyphosate and did not include the determination of its main metabolite (AMPA), which may contribute to total dietary exposure. Therefore, the glyphosate concentrations reported here should be interpreted as glyphosate-specific screening-level measurements and should not be considered representative of the complete pesticide-related chemical burden associated with glyphosate use or transformation.

Furthermore, the assessment of oil degradation was based on IV value estimation as an indicator of lipid oxidation. Although this approach does not allow the identification of specific oxidation or degradation compounds, the method demonstrated a robust correlation (R² = 0.99) for evaluating overall oil deterioration in this context. Thus, it provides a suitable screening tool to assess global structural changes in lipids associated with thermal processing, despite its limited specificity for individual compounds. Despite these limitations, the study demonstrates the feasibility of integrating agricultural and processing-related chemical hazards within a single food safety assessment framework, providing a more representative characterization of dietary exposure in institutional food environments.

4 Conclusion

This study provides an integrated assessment of chemical hazards associated with ready-to-eat corn-based foods, within a Mexican university food environment, considering both agricultural and processing-related factors. Glyphosate was detected in 90% of the analyzed samples, including 80% of tortillas and 100% of tortilla chips, with screening-level concentrations ranging from 0.107 to 1.994 mg kg⁻¹. Most analyzed samples showed concentrations above the Mexican MRL established for corn, while all remaining below Codex MRL for corn; these values were used as regulatory reference points because no specific MRL for processed corn products was identified. The dietary exposure assessment, based on a conservative screening scenario using the highest concentration observed, resulted in HQ values below 1.0 (0.0573 mg kg⁻¹ bw day⁻¹ for women and 0.0511 mg kg⁻¹ bw day⁻¹ for men), indicating estimated exposure below the selected ADI under the assumed consumption parameters. These findings provide a useful indication of glyphosate-specific dietary exposure, while further assessment including AMPA and other pesticide-related compounds would provide a more comprehensive characterization of pesticide-related exposure. The frequent occurrence of glyphosate in staple processed foods highlights the need for continued monitoring, particularly in high-consumption populations.

In addition, the significant decrease in iodine value observed after frying, based on paired comparisons, indicates changes in lipid unsaturation associated with frying. This finding highlights that ready-to-eat foods represent not only a source of exposure to agricultural contaminants but also to chemical changes associated with food preparation, thereby constituting a multifactorial exposure scenario integrating production, processing, and consumption stages.

Overall, the results emphasize the importance of integrated monitoring strategies that address agricultural residues, contaminants associated with food preparation, and other chemical changes in ready-to-eat foods. Raising awareness among agricultural stakeholders about responsible herbicide use and alternative weed-management practices may also contribute to more sustainable food production systems. Strengthening surveillance mechanisms and clarifying regulatory criteria for processed products may contribute to improved food safety management in institutional settings.

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Footnotes

Edited by: Sudhakar Srivastava, Banaras Hindu University, India

Reviewed by: Pankaj Kumar, Hemwati Nandan Bahuguna Garhwal University, India

Muhammad Umer, Hainan University, China