Analysis of quality and antibiotic residues in raw milk marketed informally in the Province of Pichincha – Ecuador

ABSTRACT

In Ecuador, more than 50% of the milk produced was informally marketed, consequently, the mean of this study was to assess the quality of this milk specifically within the province of Pichincha, the largest milk producer. A total of 650 samples were gathered from the eight cantons within the province. The parameters that exhibited the highest levels of non-compliance, of Ecuadorian legislation, were titratable acidity, accounting for 72.77% of the samples, and protein stability, accounting for 49.34%; these findings indicate a significant presence of bacterial contamination. Concerning antibiotic detection, a frightening 28.46% of the samples tested positive for residues exceeding the maximum limits established by the Codex Alimentarius. The findings indicate that a significant proportion of milk sold through informal channels in Pichincha province-Ecuador poses a substantial risk to public health.

KEYWORDS:

• Informal milk
• quality
• Pichincha
• Ecuador

Highlights

In 2022, Ecuador’s daily milk production reached 5.5 million litres. A significant portion of this milk, exceeding 50%, was informally marketed without undergoing any safety control measures. Consequently, the mean of this study was to assess the quality of this milk specifically within the province of Pichincha; this sector of Ecuador, is not only the largest milk producer, but also home to Quito, the capital city of the country. A total of 650 samples were gathered from the eight cantons within the province; these samples were subsequently subjected to analysis in order to determine their nutritional composition, utilising CombiFoss equipment. Additionally, physicochemical analysis was conducted through titratable acidity tests, specifically measuring Dornic degrees. Relative density was determined using a thermo lacto densimeter, while protein stability was assessed using 68% alcohol. Lastly, the detection of antibiotic residues was carried out by employing test strips. The parameters that exhibited the highest levels of non-compliance were titratable acidity, accounting for 72.77% of the samples, and protein stability, accounting for 49.34%. These findings indicate a significant presence of bacterial contamination. Furthermore, concerning antibiotic detection, a concerning 28.46% of the samples tested positive for residues exceeding the maximum limits established by the Codex Alimentarius. In the other parameters, there is a lower incidence of non-compliance, with a relative density of 22%, somatic cells at 22.77%, and nutritional factors (such as fat, protein, lactose, total solids, and non-fat solids) exhibiting non-compliance rates ranging from 9% to 26%. The findings indicate that a significant proportion of milk sold through informal channels in the 8 cantons of the Pichincha province poses a substantial risk to public health. Therefore, it is imperative to address this issue by implementing stringent governmental regulations and providing comprehensive training programmes for milk producers and vendors.

Introduction

Safe cow’s milk is considered a complete food for humans, which can be used to produce a large number of dairy derivatives, providing better nutritional, oxidative and even probiotic contributions (Ortega et al., 2019; Scholz-Ahrens et al., 2020) When milk is not innocuous, there is a notable decrease in nutritional value due to alteration in composition with an increase in microbiological risk due to contamination and there may be the presence of antibiotic residues due to inappropriate use of antibiotics (Sugrue et al., 2019) Non-compliance with the parameters established for the quality of raw milk, implies a detriment for both the consumer and the producer, since the former receives food with poor sanitary, nutritional or organoleptic conditions, at the same time there is a considerable decrease in the productive profitability of the animals (Fusco et al., 2020; Martin et al., 2023; Metz et al., 2020).

Ecuador produced, in 2022, 5.5 million litres of milk per day, of which the vast majority was destined for sale in liquid form, the province of Pichincha is the largest milk producer with about 19% of total production (INEC- ESPAC, 2022). Per capita, consumption was between 90 and 105 litres per person per year, which is below the 150 litres recommended by the World Health Organization (EKOS, 2019). The Ecuadorian dairy production chain generates approximately 1.3 million sources of employment, where about 65% of the total milk produced comes from small and medium-sized producers (Torres Gutiérrez & Moncayo, 2018). The majority of industrialisation processes are carried out in an artisanal manner (CIL, 2015, 2019).

Although dairy production has increased by 18.5% in the last 10 years, it has been growing at a faster rate than in the past 10 years (Fundación Heifer Ecuador, 2021), but due to the COVID-19 pandemic, between 2020 and 2021 it decreased by about 7% (CFN, 2022). The Ecuadorian Technical Standard (NTE) INEN, indicates the quality parameters that milk must meet to be considered fit for human consumption in Ecuador (INEN, 2012). A fundamental problem of the production chain in Ecuador is that more than 50% of the commercialisation is informal, it does not reach industrialisation, so there is no adequate management to ensure its quality and safety (Terán, 2019)

Considering the substantial portion of Ecuadorian milk production that is informally marketed without regulatory oversight, coupled with the prominence of milk production in the province of Pichincha, this study aims to assess the quality of raw milk sold through informal channels in this region. The evaluation will encompass physical-chemical, nutritional, and hygienic analyses, as well as the detection of antibiotic residues, with the ultimate goal of ascertaining the safety of this widely consumed milk in Ecuador.

Methodology

Population and samples

The study was of descriptive longitudinal observational type, it was carried out by taking samples, at convenience, of raw milk marketed informally in the 8 cantons of the province of Pichincha-Ecuador, on 4 occasions, with an interval of 15 days each between the months of July and September 2022. It has been collected in markets, free fairs, butcher shops, homes, greengrocers, greengrocers, vehicles, ice cream shops, bakeries, hairdressers, restaurants, third parties, stores, street vendors, etc. At the end of the research, a total of 650 samples of raw milk informally marketed in the 8 cantons of the province of Pichincha-Ecuador were collected.

Sampling and laboratory analysis:

Prior to collection, two containers were prepared for each sample: one without the preservative and the other with a volume of 50 ml, containing a bronopol preservative tablet; both bottles were labelled using an alphanumeric code. For sampling, the guidelines established in NTE INEN ISO 707 were applied as far as possible, and the samples were stored in a cooler to maintain the cold chain (2–6°C) with the aid of refrigerant gels. The contents of the milk were then poured into the respective labelled containers for analysis in less than 72 h post-sampling at the Milk Quality Control Laboratory of the Autonomous Government of the Province of Pichincha (GADPP), located at the Uyumbicho Experimental Center belonging to the Faculty of Veterinary Medicine of the Central University of Ecuador, in the Mejía canton, southeast of Quito.

Nutritional (fat percentage, protein, total solids, total solids, non-fat solids, lactose) and hygienic (somatic cell count) parameters of the milk were analysed using the Combifoss automatic analyzer containing the Milkcoscan and Fossomatic kits (FOSS, Nils Foss Alle 1, DK-3400, Hilleroed – Denmarck); the presence of antibiotics using AMINO 3IN1 and 3IN1 BTS test strips (Shenzhen Bioeasy Biotechnology Co., Ltd., Shenzhen, Guangdong Province, China 518101), relative density by means of the lactodensimeter test, titratable acidity by the Dornic degree technique, and protein stability with the 68% alcohol test.

Statistical analysis

The data obtained were stored in a Microsoft Excel spreadsheet. The free statistical programme “R Studio” version 1.2.5019 (RStudio Inc. Boston, MA, USA) was used for data analysis, using a significance of p < 0.05. Descriptive statistical analysis was performed and percentage frequency tables were used for compliance.

For the quantitative results (% fat, protein, total solids, non-fat solids, lactose, somatic cell count, relative density and titratable acidity), an analysis of the normality of the data was performed using the Kolmogorov-Smirnov test, observing that all parameters do not follow a normal distribution, since the p-value was < 0.05, so non-parametric tests were used (Kruskal Wallis test for the comparison of means, and when necessary a post-hoc analysis using the Mann-Whitney test with a Bonferroni correction); these data were compared by sampling and between cantons.

Results

Total results

Table 1 describes the values obtained for the parameters analysed for all the samples, including the minimum, maximum and average values, as well as the level of compliance in general and for each parameter, with respect to the Ecuadorian legislation NTE INEN 9. It was determined that only 5.69% (37/650) of the samples comply with all the reference values of the national regulations, while 94.31% (613/650) do not comply with any of the evaluated parameters, where the great majority of the milk is not suitable for human consumption. When comparing between cantons, the percentage of non-compliance is 100% in Mejia (72/72), Puerto Quito (12/12), Rumiñahui (64/64) and San Miguel de los Bancos (12/12); followed by Cayambe with 95% (19/20), Quito with 92.86% (403/434), Pedro Vicente Maldonado 91.67% (11/12) and Pedro Moncayo 83.33% (20/24).

Table 1. Minimum, maximum and average values and their compliance in relation to NTE INEN 9: total results.

Parameter	Requirement NTE INEN 9	Minimum Value	Maximum Value	Media	P value between samples	P value between cantons	Complies	Does not comply
Relative density (g/ml)	1.028–1033	1.015	1.040	1.030	0.4132	0.06259	507/650	143/650
							78.00%	22.00%
Titratable acidity (° D)	13–17	12	20.29	55	0.02221*	0.00029 *	177/650	473/650
							27.23%	72.77%
Fat (%)	Min. 3.2	0.75	16.94	4.39	0.00157*	6.28e-06 *	569650	81/650
							87.54%	12.46%
Crude protein (%)	Min. 2.9	1.33	4.88	3.19	0.3202	0.5803	554/650	96/650
							85.23%	14.77%
Total Solids (%)	Min. 11.2	4.72	12.94	25.86	0.000817*	1.49e-05*	588/650	62/650
							90.46%	9.54%
Non-fat solids (%)	Min. 8.2	4.64	8.56		0.07034	0.03113	548/650	102/650
							80.31%	15.69%
Lactose (%)	4.8–5.5	2.650	8.72	4.60	2.26e-05*	0.0051*	477/650	173/650
							73.38%	26.62%
Somatic cells (CS/ml)	Max. 700000	4000	10235000	581900	0.06941	0.00026*	502/650	148/650
							77.23%	22.77%
TOTAL:							37/650	613/650
							5.69%	94.31%

Given that the parameters evaluated of the 650 samples analysed, the non-compliance, from highest to lowest, is as follows: titratable acidity with 72.77% (473/650), protein stability with 49.34% (322/650) of non-compliance, presence of antibiotic residues 28.46% (185/650), somatic cell count 22.77% (148/650), relative density with 22.00% (143/650); in all these cases, milk is considered unfit for human consumption. Regarding nutritional properties, the non-compliance in relation to the percentage of lactose is 26.62% (173/650), non-fat solids 15.69% (102/650), protein 14.77% (96/650), fat 12.46% (81/650) and total solids 9.54% (62/650); in these cases, in spite of not reaching the parameters established by the regulations, the milk could be considered fit for consumption, as long as it does not fail to comply with the aforementioned parameters.

Relative density

Regarding relative density, 22.00% (507/650) of the samples were found to be outside the range stipulated by local legislation (from 1.028 to 1.033 g/ml), where 34 samples (6.7%) were above the maximum allowed, suspecting skim milk, while 93.29% (473/507) of the samples, their values were found to be below the minimum required, being an indicator of adulteration with water in the milk; the remaining 22.00% (143/650) met the permitted range for relative density. The overall mean was 1.030 g/ml, with a range between 1.015 and 1.040 g/ml (Table 1). When the data obtained were compared statistically, no significant differences were found between samples (p value: 0.4132) or between the cantons studied (p value: 0.06259), as shown in Table 1 and Figures 1 and 2.

Figure 1. Boxplot of density, acidity and somatic cell count, evaluated between cantons.

Figure 2. Boxplot of density, acidity and somatic cell count, evaluated between cantons.

Titratable acidity

As for thiulable acidity, it is the parameter with the lowest compliance, since 72.77% (473/650) of the samples were found to be outside the range allowed by local legislation (13–17° D) and only 27.23% (177/650) were within the same range. Of the 473 samples outside the range, three (0.63%) had an acidity of 12° D and a density below 1.020 g/ml, indicating that they were adulterated with a large amount of water; while 99.37% (470/473) exceeded the maximum acidity limit, demonstrating a high bacterial load in the milk tested and a potential public health hazard. The mean titratable acidity was 20.29°D, being well above the permitted range with a maximum value of 55°D and a minimum of 12°D (Table 1 and Figures 1 and 2). Significant differences (p value < 0.05) were found both between samples and between the cantons studied (Table 1). In the first case, the difference was between the third and fourth sampling; in the case of the cantons, the values found in the canton Cayambe are different from those found in the cantons Mejia, Quito, Pedro Vicente Maldonado and Rumiñahui.

Protein stability

By performing the 68% alcohol test, it was found that of the 650 samples analysed, 49.34% (322/650) were positive due to loss of protein stability probably associated mainly with an increase in the titratable acidity of the milk due to bacterial contamination, representing a danger, since the milk under these conditions could not be pasteurised; the remaining 50.46% (328/650) of samples maintain this stability intact and can withstand the heat treatments.

Somatic cells

The Ecuadorian standard accepts a maximum permitted limit of 700,000 CS/ml, which is much higher than international legislation, which allows a maximum of 200,000 CS/ml to 400,000 CS/ml. When comparing the results based on the Ecuadorian standard, we found that 22.77% (148/650) do not comply with local legislation, since they present counts higher than the maximum allowed, while the remaining 77.23% (502/650), present values lower than it, with an average of 581,900 CS/ml and a range between 4000 and 10,235,000 CS/ml (Table 1 and Figures 1 and 2). When compared with international standards, we found that only 15.08% (98/650) of the samples have values lower than 200,000 CS/ml, indicating an optimal health status of the mammary gland, 23.23% (151/650) between 200,001 and 400,000 CS/ml, and 46.00% (299/650) more than 400,000 CS/ml (Table 1 and Figures 1 and 2). After performing the statistical analysis, no significant differences were found between samples (p value: 0.06941), but between cantons (p value: 0.00026), being different between Cayambe and Pedro Moncayo.

Fat

Regarding fat percentage, 12.46% (81/650) of the samples were found to be below the minimum stipulated by local legislation (3%), while 87.54% (569/650) were above it. The mean of the study was 4.39% (above the minimum required), with a minimum value of 0.75% and a maximum of 16.94% (Table 1 and Figure 2).

For this parameter, there were statistically significant differences (p value < 0.05) both between samples and between the cantons studied. There were differences between the second sampling and the first and fourth sampling, as well as between the canton Rumiñahui and the cantons Mejia, Pedro Moncayo and Quito (Table 1).

Lactose

The percentage of lactose shows that 26.62% (173/650) of the samples are below the international standard (NTE INEN 9 does not indicate reference values for lactose), while 73.38% (477/650) meet the minimum requirement of 4.8%; an average of 4.60% was determined, with a range between 2.65% and 8.72%. Significant differences were found (p value < 0.05) both between samples (fourth vs. first, second and third) and between cantons (Pedro Moncayo-Mejia, Rumiñahui and Quito), as detailed in Table 1 and Figures 2 and 3.

Figure 3. Boxplot of fat, protein, lactose, total solids and solids-non-fat, evaluated between samples.

Total solids

The percentage of total solids showed that 9.54% (62/650) did not meet the reference value (minimum 11.2%) while 90.46% (588/650) did; the minimum value found was 4.72%, the maximum 25.86% and an average of 12.94% (Table 1). In the statistical analysis, significant differences were found (p value < 0.05) with respect to the samples and the cantons studied, with the values of the second sample being different compared to the rest of the samples; in the case of the cantons, there are differences between Rumiñahui, Mejia, Quito and Pedro Moncayo, as well as between Puerto Quito and Pedro Moncayo (Table 1 and Figures 2 and 3).

Protein

The protein percentage has 14.77% (96/650) of the samples are below the Ecuadorian standard (min 2.9%), while 82.23% (554/650) meet the minimum requirement; likewise, a mean of 3.19% was found, with minimum and maximum values of 1.33% and 4.88%, respectively. No significant differences were found between cantons (p value: 0.5803) and samples (p value: 0.3202), as shown in Table 1 and Figures 2 and 3.

Non-fat solids

In the case of non-fat solids, 15.69% (102/650) of the milk analysed did not meet the minimum reference value (8.2%), while 80.31% (548/650) had values above it, with a minimum value of 4.64% and a maximum of 10.04%, with an average of 8.56% (Table 1). There were no significant differences between cantons (p value: 0.03113) or between samples (p value: 0.07034) (Figure 4).

Figure 4. Boxplot of fat, protein, lactose, total solids and solids-non-fat, evaluated between samples.

Antibiotic residues

Using test strips, 28.46% (185/650) of the samples were found to be positive for antibiotic residues above the maximum limits allowed by the Codex Alimentarius. Of the 185 positive samples, 0.54% (1/185) were for gentamicin, 3.79% (7/185) for streptomycin, 3.24% (6/185) for beta-lactams, 4.32% (8/185) for tetracyclines, 9.19% (17/185) for neomycin and 82.16% (152/185) for sulfonamides, as detailed in Table 2.

Table 2. Positive results by antibiotic family.

Antibiotic	Positive samples	Percentage
Gentamicin	1/185	0.54%
Streptomycin	7/185	3.79%
Betalactams	6/185	3.24%
Tetracyclines	8/185	4.32%
Neomycin	17/185	9.19%
Sulfonamides	152/185	82.16%

When comparing the positivity of antibiotics in milk, among the cantons of the study, we found that in Mejia the non-compliance is in 59.72% (43/72) of the samples, followed by Cayambe with 35% (7/20), Pedro Moncayo 29.17% (7/24), Rumiñahui 25.00% (16/64), Quito: 24.65% (107/434), Pedro Vicente Maldonado 16.67% (2/12), San Miguel de los Bancos: 16.67% (2/12) and Puerto Quito with 8.33% (1/12) of the milk analysed.

Discussion

There are studies in Ecuador that demonstrate the presence of bacterial contamination, adulterants and contaminants in raw milk, with great heterogeneity between the different investigations (Puga-Torres et al., 2022), but there is only one previous study on the quality of milk sold informally in the province of Pichincha-Ecuador (Guamán & Puga-Torres, 2022). Our results determined that 94.31% (613/650) of the samples analysed do not comply with at least one parameter established in the Ecuadorian INEN 9 standard, which requires higher values than the results found in the Rumiñahui canton of the province of Pichincha, where 74% (74/100) of the samples informally marketed do not comply with the provisions of the local legislation (Guamán & Puga-Torres, 2022). When comparing our results with an international study conducted in Colombia, where 96 samples of milk sold by street vendors were collected, it was determined that 100% of them did not comply with the current regulations in that country (Chamorro et al., 2010) It is important to mention that our study was conducted in milk marketed informally, since studies conducted in collection centres and small farms in Cayambe and Pedro Moncayo-Pichincha, whose milk is marketed to the industry, the non-compliance is totally different, since only 6.81% (9/132) of the samples had this difficulty, which demonstrates the importance of quality control performed by the dairy industry (Salguero et al., 2023).

The results of this work also show a high non-compliance in the titratable acidity parameter 72.77%, which are values much higher (46%) than those indicated in samples of informal milk sales in the Rumiñahui canton of Pichincha (Guamán & Puga-Torres, 2022). Although milk is practically sterile inside the mammary gland, when it is extracted it suffers from microbial contamination, by psychrophilic, beneficial and also pathogenic microorganisms, the main ones being: Pseudomonas, E. coli, Acinetobacter, Lactococcus, Flavobacterium, bacteria of the family Enterobacteriaceae and others; therefore, hygienic deficiencies at the time of milking, storage and/or transport of milk, including lack of refrigeration, increase the number of microorganisms (Li et al., 2023; Martin et al., 2023; Metz et al., 2020). In the present study, it was evidenced that most of the milk sampled was not in the cold chain at the time of marketing, which causes the high environmental temperatures to increase the bacterial count, causing the transformation of lactose into lactic acid (Bettera et al., 2023). As for the protein stability parameter, the positive result in about half of the samples gives us the indication that the milk undergoes acidification processes with changes in pH, which cause modification in the casein micelle, especially in the balance of calcium and phosphate (Eshpari et al., 2017), which causes structural changes in milk and derivatives, and which can be improved with the implementation of good management practices and even with hazard analysis and critical control points (HACCP) system (Mannani et al., 2023).

Regarding relative density, our non-compliance results (22%) are also similar to those reported by Guamán and Puga-Torres (2022), who determined that 26% (26/100) of the samples of informal milk sales had this parameter altered in the Rumiñahui canton. When lower levels of density are found, they may be due to adulteration with water in the milk, and to a lesser extent due to deficiencies in energy and protein intake in the diet, while high values are indicators of extraction of the fatty part of the milk (Alichanidis et al., 2016; Gondim et al., 2017). Under physiological conditions, the density of milk varies according to the climatic season, days of lactation, parity, diets, and genetics (Parmar et al., 2020).

The importance of antibiotics in human and animal health is well known; however, its indiscriminate use has been associated with antimicrobial resistance and the loss of intestinal microbiota, with foods of animal (such as milk) origin being a vehicle for the entry of these xenobiotics into the consumer’s body (Santacroce et al., 2023). Our research reported 28.46% of samples analysed above the maximum permissible limits; these values are quite high compared to those reported by Guamán and Puga-Torres (2022), who found 7% of samples with antibiotic residues, where 85.71% corresponded to tetracyclines and 14.29% to beta-lactams. If we compare with other studies conducted in Ecuador, also in informal milk sales, we find diverse scenarios; for example, similar data are obtained in the study conducted in markets of Cuenca-Azuay, who reported values of 26% positivity in 150 milk samples, where the family mostly found corresponds to beta-lactams and tetracyclines (Caracundo, 2019). In another study conducted in vehicles in the same city of Cuenca, the presence of antibiotic residues was 71.15%, with the vast majority being beta-lactams and the rest tetracyclines (Castro & Suárez, 2017). Likewise, in the province of Cañar, it was determined that even 61% of the milk analysed contained beta-lactams, tetracyclines and/or sulfonamines (Duy & Garnica, 2020). Lower values were found in the province of Guayas, where informally marketed milk had 19.4% antibiotic residues (Aroca & Álvarez, 2016). When studies are conducted in raw milk that goes to the industry, this reality is different because in the vast majority of cases these drugs are not found in milk, as reported in the study of Salguero et al. (2023). It is important to mention that the milk that is marketed informally in Ecuador comes mostly from small producers who do not have the advice of a veterinarian and therefore inadequately use these drugs, which are very important for the treatment of dairy cows (Bacanli & Başaran, 2019; Kumar & Gupta, 2018). In a meta-analysis study, from 1992 to 2021, taking 140 investigations worldwide, of milk and dairy derivatives, a prevalence of 33.36% was found, with a high presence of S. aureus, and with resistance to antimicrobials mainly in the group of beta-lactams; precisely, in the case of S. aureus, raw milk is considered an important vehicle for its presence and is significantly associated with antimicrobial resistance (Pahlavanzadeh et al., 2021; Zhang et al., 2022).

The presence of somatic cells in milk is associated with the health of the mammary gland, where mastitis is one of the most common diseases in dairy cattle and the one that causes the greatest economic impact, not only in animal health, but also in the quality of the milk and the derivatives manufactured from it, since considerable changes have been found in the composition, coagulation, cheese yield and nutrient recovery (Pegolo et al., 2021). Regarding this parameter, Ecuadorian regulations are quite permissible, accepting a maximum of 700,000 CS/ml, finding in this study that 22.77% (148/650) of the samples exceeded this maximum allowed; these data are quite similar to those found in the Rumiñahui canton, where a non-compliance of 21% of the milk samples was determined (Guamán & Puga-Torres, 2022). Values lower than 200,000 CS/ml reflect a good sanitary state of the mammary gland, which translates into an optimal lactose formation and as a consequence a correct milk volume, which leads to economic benefits for the producers (Alhussien & Dang, 2018; Valdivia et al., 2021) The increase of the same, are synonymous with subclinical or clinical mastitis, related to poor hygienic management mainly in the milking stage (Jurado-Gámez et al., 2020). The main cause of mastitis is a decrease in production yields as well as alterations in the nutritional, organoleptic and conservation characteristics of milk and its by-products (Sharun et al., 2021).

In relation to the nutritional parameters analyzed, the percentage of compliance is much higher than those previously indicated, with 87.54% of the samples showing values higher than those established by local standards for fat, 82.23% for protein, 90.46% for total solids, 80.31% for non-fat solids and 73.38% for lactose (Table 1), which is similar to that indicated by Guamán and Puga-Torres (2022), who reported compliance of more than 74% for these nutritional parameters.

To maintain good nutritional quality of milk, it is necessary for the cow to have good availability of glucose and amino acids, therefore, general animal health, diet, a healthy rumen and a mammary gland in optimal conditions are very important; in addition, the breed of the animal, the lactation period and other physiological considerations of the cows play a role (Gross, 2022). Referring to fat, it has a great variability in milk, as it depends on the breed of the animal, its physiological and health status and the diets received by them (Ambuludi et al., 2017). The percentage of protein also depends on nutrition, since reduced levels of protein in the diet are reflected with low levels in milk, although in grazing animals (as the vast majority of animals in Ecuador) where their diets are based on grasses and legumes, good levels of protein in milk are generally found (Magan et al., 2021). In the case of total solids, the percentage of milk fat is quite influential in it, although any increase or decrease of the rest of the solid components makes their levels vary (Guevara-Freire et al., 2019). The volume of milk is inversely proportional to the content of total solids, since its increase causes a decrease in these components (Acosta et al., 2020). On the contrary, lactose is directly proportional to milk volume, i.e. an increase in the synthesis of this carboxy-hydrate causes an increase in milk volume, while its decrease reduces the amount of milk produced, as happens in mastitis whose inflammation of the mammary gland causes changes in capillary permeability, altering the osmotic balance, which leads to a lower production of lactose in the lactocyte and therefore a decrease in milk volume (Costa et al., 2019).

Conclusions

This study presents significant and concerning findings derived from samples of unregulated raw milk sold in the province of Pichincha, which is the primary milk-producing region in Ecuador and home to the country’s capital, Quito. The study revealed a significant proportion of samples (94.31%) that fail to meet the requirements outlined in the Ecuadorian legislation regarding raw milk. The majority of these samples are deemed unsuitable for human consumption. Of particular concern is the notably high percentage of samples (28.46%) that exceed the maximum allowable limit for antibiotic residues. Additionally, the parameter with the highest rate of non-compliance is titratable acidity (72.77%), indicating a substantial bacterial presence in the samples. Hence, it is advisable to develop and execute training initiatives targeting small-scale milk producers and vendors, with a particular focus on the potential hazards arising from non-adherence to established standards, particularly those pertaining to antibiotic residues. Additionally, these programmes should underscore the economic advantages associated with enhancing the overall quality of the end product.

Acknowledgment

This research was funded by the General Directorate of Research of the Central University of Ecuador. A special thanks to Autonomous Government of the Province of Pichincha (GADPP), for their valuable collaboration.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by Universidad Central del Ecuador (project Code: DI-CONV-2022-002).