Quality and antibiotic residues in raw milk sold informally in Manabí and Santo Domingo de los Tsáchilas, Ecuador

This study aims to evaluate the quality and presence of antibiotic residues in raw cow’s milk marketed through informal channels in the provinces of Santo Domingo de los Tsáchilas and Manabí, Ecuador. A total of 406 samples were collected between April 2023 and August 2024. Only 12.32% (50/406) met the requirements established by the Ecuadorian Technical Standard INEN 9, while 87.68% (356/406) failed to comply with at least one quality parameter. The most frequent non-conformities were observed when analyzing pH (72.41%), titratable acidity (68.72%), and protein stability (55.67%), likely reflecting deficient hygienic practices during production and handling. Furthermore, 6.40% (26/406) of the samples tested positive for antibiotic residues. These findings underscore significant shortcomings in milk quality within informal markets and underscore the potential public health risks associated with consuming improperly handled raw milk in these Ecuadorian provinces.

Abbring S, Hols G, Garssen J, van Esch BCAM, 2019. Raw cow’s milk consumption and allergic diseases – The potential role of bioactive whey proteins. Eur J Pharmacol 843:55-65. DOI: https://doi.org/10.1016/j.ejphar.2018.11.013

Alhussien MN, Dang AK, 2018. Milk somatic cells, factors influencing their release, future prospects, and practical utility in dairy animals: an overview. Vet World 11:562-77. DOI: https://doi.org/10.14202/vetworld.2018.562-577

Alichanidis E, Moatsou G, Polychroniadou A, 2016. Composition and properties of non-cow milk and products. In: Tsakalidou E, Papadimitriou K, eds. Non-bovine milk and milk products. Academic Press, Cambridge, MA, USA, pp 81-116. DOI: https://doi.org/10.1016/B978-0-12-803361-6.00005-3

Almashhadany DA, 2021. Screening of antibiotic residues in raw milk of cows and buffalos by diffusion assays. Ital J Food Saf 10:9034. DOI: https://doi.org/10.4081/ijfs.2021.9034

Alves JS, de Moura Souza R, de Lima Moreira JP, Gonzalez AGM, 2024. Antimicrobial resistance of Enterobacteriaceae and Staphylococcus spp. isolated from raw cow’s milk from healthy, clinical and subclinical mastitis udders. Preventive Veterinary Medicine, 227, 106205. DOI: https://doi.org/10.1016/j.prevetmed.2024.106205

Arias-Sandoval CA, Bonifaz-García NF, 2025. Compositional, hygienic and sanitary quality of bovine milk in three regions of Ecuador. Rev Med Vet Zoot 72:114348. DOI: https://doi.org/10.15446/rfmvz.v72n1.114348

Artursson K, Schelin J, Thisted Lambertz S, Hansson I, Olsson Engvall E, 2018. Foodborne pathogens in unpasteurized milk in Sweden. Int J Food Microbiol 284:120-7. DOI: https://doi.org/10.1016/j.ijfoodmicro.2018.05.015

Bettera L, Levante A, Bancalari E, Bottari B, Gatti M, 2023. Lactic acid bacteria in cow raw milk for cheese production: Which and how many? Front Microbiol 13: 1092224. DOI: https://doi.org/10.3389/fmicb.2022.1092224

Condé VA, de Freitas Silva Valente G, Minighin EC, 2020. Milk fraud by the addition of whey using an artificial neural network. Ciência Rural 50:e20190312. DOI: https://doi.org/10.1590/0103-8478cr20190312

Costa A, Bovenhuis H, Egger-Danner C, Fuerst-Waltl B, Boutinaud M, Guinard-Flament J, Obritzhauser W, Visentin G, Penasa M, 2025. Mastitis has a cumulative and lasting effect on milk yield and lactose content in dairy cows. J Dairy Sci 108:635-50. DOI: https://doi.org/10.3168/jds.2024-25467

De Souza Gondim C, Junqueira RG, de Carvalho Souza SV, Ruisánchez I, Callao MP, 2017. Detection of several common adulterants in raw milk by MID-infrared spectroscopy and one-class and multi-class multivariate strategies. Food Chem 230:68-75. DOI: https://doi.org/10.1016/j.foodchem.2017.03.022

Eshpari H, Jimenez-Flores R, Tong PS, Corredig M, 2017. Thermal stability of reconstituted milk protein concentrates: Effect of partial calcium depletion during membrane filtration. Food Res Int 102:409-18. DOI: https://doi.org/10.1016/j.foodres.2017.07.058

Fusco V, Chieffi D, Fanelli F, Logrieco AF, Cho G, Kabisch J, Böhnlein C, Franz CMAP, 2020. Microbial quality and safety of milk and milk products in the 21st century. Comprehensive Rev Food Sci Food Saf 19:2013-49. DOI: https://doi.org/10.1111/1541-4337.12568

Guamán A, Puga-Torres B, 2022. Determinación de la calidad y detección de residuos antibióticos en leche cruda de bovino comercializada informalmente en Cantón Rumiñahui-Pichincha. Available from: http://www.dspace.uce.edu.ec/handle/25000/27751. [Thesis in Spanish].

Hanrahan L, McHugh N, Hennessy T, Moran B, Kearney R, Wallace M, Shalloo L, 2018. Factors associated with profitability in pasture-based systems of milk production. J Dairy Sci 101:5474-85. DOI: https://doi.org/10.3168/jds.2017-13223

Hanuš O, Kučera J, Samková E, Němečková I, Čítek J, Kopec T, Falta D, Nejeschlebová H, Rysová L, Klimešová M, Elich O, 2021. Raw Cow Milk Protein Stability under Natural and Technological Conditions of Environment by Analysis of Variance. Foods 10:2017. DOI: https://doi.org/10.3390/foods10092017

Hossain D, Singha S, Thof V, Gough S, Uddin AM, 2021. Effect of somatic cells on milk quality and human health. Vet Sci Res Rev 7:31-4. DOI: https://doi.org/10.17582/journal.vsrr/2021/7.1.31.34

Ichimura T, 2024. Yogurt production. Methods Mol Biol 2851:63-74. DOI: https://doi.org/10.1007/978-1-0716-4096-8_5

INEC-ESPAC, 2023. Encuesta de superficie y producción agropecuaria continua. ESPAC 2022. Available from: https://www.ecuadorencifras.gob.ec/documentos/web-inec/Estadisticas_agropecuarias/espac/espac_2022/PPT_ ESPAC_ 2022_04.pdf. [Material in Spanish].

INEN, 2012. Leche cruda: Requisitos NTE INEN 9. Avaiable from: https://www.gob.ec/sites/default/files/regulations/2018-10/Documento_BL NTE INEN 9 Leche cruda Requisitos.pdf. [Material in Spanish].

INEN, 2014. Leche y productos lácteos. Directrices para la toma de muestras (ISO 707:2008, IDT) (pp. 1-49). Available from: https://silo.tips/download/nte-inen-iso-707-primera-edicion

Khaldi Z, Nafti M, Jilani MT, 2022. Baseline composition and microbial quality assessment of raw milk from small ruminants and Maghrebi camels in the oasis area of Tunisia. Trop Anim Health Prod 54:391. DOI: https://doi.org/10.1007/s11250-022-03408-z

Liu J, Zhu Y, Jay-Russell M, Lemay DG, Lemay DG, Lemay DG, Mills DA, Mills DA, Mills DA, 2020. Reservoirs of antimicrobial resistance genes in retail raw milk. Microbiome 8:99. DOI: https://doi.org/10.1186/s40168-020-00861-6

Liu J, Ren J, Liu ZM, Guo BH, 2015. A new comprehensive index for discriminating adulteration in bovine raw milk. Food Chem 172:251-6. DOI: https://doi.org/10.1016/j.foodchem.2014.09.063

Magan JB, O’Callaghan TF, Kelly AL, McCarthy NA, 2021. Compositional and functional properties of milk and dairy products derived from cows fed pasture or concentrate‐based diets. Compr Rev Food Sci Food Saf 20:2769-800. DOI: https://doi.org/10.1111/1541-4337.12751

McHugh A, Feehily C, Fenelon M, Gleeson D, Hill C, Cotter P, 2020. Tracking the dairy microbiota from farm bulk tank. mSystems 5:1-16. DOI: https://doi.org/10.1128/mSystems.00226-20

Mohamed MA, Elmi AAS, Dubad AB, Hassan YHS, Osman AM, Bitrus AA, 2020. Antibiotic residue in raw milk collected from dairy farms and markets in Benadir, Somalia. PAMJ One Health 2:1-8. DOI: https://doi.org/10.11604/pamj-oh.2020.2.19.24814

Nawaz T, Ur Rehman Z, Ullah R, Ahmed N, Mahmoud Sayed S, 2022. Physicochemical and adulteration study of fresh milk collected from different locations in Pakistan. Saudi J Biol Sci 29:103449. DOI: https://doi.org/10.1016/j.sjbs.2022.103449

Obladen M, 2014. From swill milk to certified milk: progress in cow’s milk quality in the 19th century. Ann Nutr Metab 64:80-7. DOI: https://doi.org/10.1159/000363069

Pahlavanzadeh S, Khoshbakht R, Kaboosi H, Moazamian E, 2021. Antibiotic resistance and phylogenetic comparison of human, pet animals and raw milk Staphylococcus aureus isolates. Comp Immunol Microbiol Infect Dis 79:101717. DOI: https://doi.org/10.1016/j.cimid.2021.101717

Piston R, Zabilansky B, Bloom J, 2014. Guidelines for raw milk quality tests. Available from: https://www.caaeonline.org/uploads/1/0/8/6/108695529/milk_quality_reading_material.pdf.

Puga-Torres B, Aragón E, Contreras A, Escobar D, Guevara K, Herrera L, López N, Luje D, Martínez M, Sánchez L, Tapia D, Villarreal T, Núñez L, 2024. Analysis of quality and antibiotic residues in raw milk marketed informally in the Province of Pichincha - Ecuador. Food Agric Immunol 35:2291321. DOI: https://doi.org/10.1080/09540105.2023.2291321

Puga-Torres B, Aragón Vásquez E, Ron L, Álvarez V, Bonilla S, Guzmán A, Lara D, De la Torre D, 2022. Milk quality parameters of raw milk in Ecuador between 2010 and 2020: a systematic literature review and meta-analysis. Foods 11:3351. DOI: https://doi.org/10.3390/foods11213351

Rahman S, Hassan MM, Chowdhury S, 2021. Determination of antibiotic residues in milk and assessment of human health risk in Bangladesh. Heliyon 7:e07739. DOI: https://doi.org/10.1016/j.heliyon.2021.e07739

Renhe IRT, Perrone ÍT, Tavares GM, Schuck P, de Carvalho AF, 2019. Physicochemical Characteristics of Raw Milk. In: Nero LA, Fernandes De Carvalho A, eds. Raw milk. Academi Press, Cambridge, MA, USA, pp 29-43. DOI: https://doi.org/10.1016/B978-0-12-810530-6.00002-X

Riveros-Galán DS, Obando-Chaves M, 2020. Mastitis, somatic cell count, and its impact on dairy-product quality… An omission in Colombia?: a review. Rev Colom Cienc Pecua 34:241-53. DOI: https://doi.org/10.17533/udea.rccp.v34n4a01

Santacroce L, Di Domenico M, Montagnani M, Jirillo E, 2023. Antibiotic resistance and microbiota response. Curr Pharm Des 29:356-64. DOI: https://doi.org/10.2174/1381612829666221219093450

Sharma N, Singh NK, Bhadwal MS, 2011. Relationship of somatic cell count and mastitis: an overview. Asia-Aust J Anim Sci 24:429-38. DOI: https://doi.org/10.5713/ajas.2011.10233

Sharun K, Dhama K, Tiwari R, Gugjoo MB, Iqbal Yatoo M, Patel SK, Pathak M, Karthik K, Khurana SK, Singh R, Puvvala B, Amarpal, Singh R, Singh KP, Chaicumpa W, 2021. Advances in therapeutic and managemental approaches of bovine mastitis: a comprehensive review. Vet Q 41:107-36. DOI: https://doi.org/10.1080/01652176.2021.1882713

Silva ARA, Silva MMN, Ribeiro BD, 2020. Health issues and technological aspects of plant-based alternative milk. Food Res Int 131:108972. DOI: https://doi.org/10.1016/j.foodres.2019.108972

Singuluri H, Sukumaran M, 2014. Milk adulteration in Hyderabad, India – a comparative study on the levels of different adulterants present in milk. J Chromatograph Separat Techniq 5:1000212. DOI: https://doi.org/10.4172/2157-7064.1000212

Sumon SMMR, Parvin S, Ehsan A, Islam T, 2020. Relationship between somatic cell counts and subclinical mastitis in lactating dairy cows. Vet World 13:1709-13. DOI: https://doi.org/10.14202/vetworld.2020.1709-1713

Techane T., 2023. Effect of adulterants on quality and safety of cow milk: a review. Int J Diabetes Metab Disord 8:277-87. DOI: https://doi.org/10.33140/IJDMD.08.01.02

Terán J, 2019. Análisis del mercado de la leche en Ecuador: factores determinantes y desafíos. Available from: https://riunet.upv.es/bitstream/handle/10251/124490/Terán - Análisis del mercado de la leche en Ecuador%3A factores determinantes y desafíos.pdf?sequence=1&isAllowed=y. [Thesis in Spanish].

Wang Y, Wuren T, Zhai B, Er D, Yang H, 2024. Impact of storage conditions on the quality of raw camel milk. Food Sci Anim Resour 44:1345-57. DOI: https://doi.org/10.5851/kosfa.2024.e52

Wei C, Luo HP, Wang YC, Huang XX, Zhang MH, Zhang XX, Wang D, Ge JJ, Xu L, Jiang H, Ju X, 2021. Analyses of the genetic relationships between lactose, somatic cell score, and growth traits in Simmental cattle. Animal 15:100027. DOI: https://doi.org/10.1016/j.animal.2020.100027

Zhang J, Wang J, Jin J, Li X, Zhang H, Shi X, Zhao C, 2022. Prevalence, antibiotic resistance, and enterotoxin genes of Staphylococcus aureus isolated from milk and dairy products worldwide: A systematic review and meta-analysis. Food Res Int 162:111969. DOI: https://doi.org/10.1016/j.foodres.2022.111969