Livestock Research for Rural Development 27 (12) 2015 Guide for preparation of papers LRRD Newsletter

Citation of this paper

Quality of milk in a traditional milk-cheese chain in the highlands of central Mexico

M Hidalgo-Milpa, E Sánchez-Vera and A Espinoza-Ortega

Instituto de Ciencias Agropecuarias y Rurales (ICAR) Universidad Autónoma del Estado de México Instituto Literario # 100,
Col. Centro,CP 50000, Toluca, México


The objective was to analyse the role of each actor of a traditional small-scale dairy chain in terms of the perception of quality of the milk used in a rural dairy-processing agro-industry, considering as a primordial factor the transport of milk from the farm to the processing agro-industry, emphasizing the physicochemical and bacteriologic aspects. Samples at the beginning and at the end of transportation were collected in order to obtain the physicochemical and bacteriologic analysis, the results were analyzed with a paired Student’s “t” Test, and a questionnaire was applied to obtain information regarding quality perception.

No differences were observed in the physicochemical characteristics (acidity, pH, fat, protein, SNF and density). In the bacteriological study, total aerobic mesophiles and coliforms were uncountable. In relation to temperature, all samples exceed specifications in Mexican regulation. Those who collect the largest milk volumes make longer journeys so that the increment in temperature is higher. It is concluded that the collected milk meets the requirements of the Mexican regulation in respect to physicochemical variables, except for acidity. Nevertheless, high bacterial counts are factors that affect the milk-cheese chain, where the final quality of cheese is dependant on the original milk quality, which in turn is affected by the volume of milk delivered to cheese-making agro-industry, and in the obtained yield of the final product.

Keywords: physicochemical, rural agro-industry, transport


Nowadays the chain of production and distribution of food is longer, and in most cases food reaches the consumer after undergoing several modifications and transformations. Therefore, achieving good quality involves all of the actors of the alimentary chain; from primary production to consumer (Linck et al 2006; Lara et al 2003) and the milk chain is not an exception.

World population growth and urban concentration have increased the demand for dairy products, and in parallel there is an increase in the use of new technologies and the development of new products that emphasise their nutritive, healthful, natural and traditional aspects. Booland (2001) and Hirchis (2000) mention that part of the population returns to the consumption of traditional dairy products for they plainly recognize that “the products are good for us”. Likewise Murdoch (2000) establishes that those products have gained presence in markets, reappearing as local products associated with a territory and a traditional know-how (Linck et al 2006; Pomeón et al 2007). Despite the different stances, Boor (2001) and Barbano et al (2006) have mentioned that the constant is quality, as a determining factor of a product or sub-product in the market.

Continuous improvement in milk quality requires the participation of each one of the actors that make up the production chain, so that current knowledge and experience have demonstrated that quality is not a phenomenon that can be individually achieved, but is the result of a collective action process applied to the chain as a whole, and even to a complete agro-food system. This is to say; cooperation and intervention of each one of the activities carried out will depend on the conditions of their environment, customs, social relations and the observance of official prescriptions, which intervene in the regulation of quality to achieve the product’s safety and innocuousness (Lynck et al 2006; Marsden 1998; Cesin et al 2007).

In Mexico, the dairy sector is increasingly sensitive to the importance of quality, not only due to a regulative demand in the markets, but also as a requisite to remain in them (Hirchis 2000). The concept of quality comprehends both hygienic and sanitary aspects as well as nutritive issues, which are established by the official institutions in charge of verifying the meeting of these properties (NMX-F-700-COFOCALEC-2004). In order to achieve so, the stages of collection, storing and transport of milk should be involved, as well as the interactions between the actors that are part of the agro-food chain (Chombo 1999; Boor 2001), taking into account that these interactions differ in each dairy subsystem.

The case of traditional cheeses in Mexico

The situation of Mexican traditional cheeses is scarcely studied (Cuevas et al 2007), in spite of the existence of a considerable number of varieties across the country that are locally recognized and consumed (Cervantes et al 2006). This may be their main problem, as currently local cheese-making agro-industries face two positions (Chombo 1999; Pomeón et al 2007): 1) The renewed appraisal of their products by consumers at local and regional levels due to their “traditional character”; and 2) the certification of these products as innocuous and of good quality, competitively differentiated from those industrially elaborated.

The objective of this work was to analyse the relations between the actors of the milk-cheese chain in respect to milk quality, starting from the collector as a linking element between the farms as units of primary production and the cheese-making agroindustries. In parallel, the handling of milk in this link was established and as well as its physicochemical and bacteriologic characteristics, contrasting them with the Mexican Norm.

Material and methods

The study was carried out from March to September 2007 in the Mexican central highlands, in the municipality of Aculco, State of Mexico, located at 20° 06’ North and 99° 50’ West, at 2250 m.a.s.l., and 552.5 km2 . The minimal temperatures in winter are below freezing, and the mean maximal temperature is 24° C, with a mean of 18° C. The climate is sub-humid temperate. Rural dairy-processing agro-industries characterise the municipality, are concentrated, and have relations backwards with the dairy farms and collectors that supply them with their raw material (milk), and forward relations are with cheese merchants and final consumers. In the area of study traditional cheeses are made with raw milk, which are generally marketed in informal marketplaces and cities nearby.

The milk-cheese chain is composed by 37 cheese-shops, 62 collectors and 269 small-scale dairy farms (Castañeda-Martínez, in print). The 62 collectors of the zone formed the sampling framework for this work and the sample size was determined by (Daniel 2005):




n: Sample size

N: population (62 collectors)

p: Success probability (0.63) (cheese-shops which buy from collectors)

q: Failure probability (1-p)

d: precision (0.1)

Sample size was 16 collectors; and through them it was possible to establish communication with dairy farms and cheese-makers establishing a non-probabilistic sampling procedure.


A semi-structured questionnaire was applied to each actor of the chain in order to obtain information from the perception of the concept of quality (milk-cheese), handling of milk, price, and quality requirements, besides it was also applied to the official instance in charge of regulating and verifying sanitary requirements, namely the Institute of Health of the State of Mexico (Instituto de Salud del Estado de México, ISEM).

Two journeys were made with the collectors, where the time of the journey was registered and observed, as well as the characteristics of transports and containers; these observations were contrasted against the Mexican Zoo-sanitary Norm 024. Additionally, the volume of milk and number of producers the collectors work with were recorded.

Samples of milk were collected at the beginning and at the end of the journey (twice for each container), and the milk’s temperature measured. Samples were carried for their later analysis in the laboratory in less than 24 hours.

Laboratory analysis

Physicochemical analysis: Fat (g/kg), protein (g/kg), solids non-fat (SNF) (g/kg), density (g/cm3) and added water into milk (AWM) (%) were determined using the EkomilkÒ (Exm1301p) equipment; acidity (ºDornic) expressed in g of lactic acid / 100 ml of milk and pH obtained with a potentiometer (Orion, Model 520 A).

Microbiological analysis: Aerobic mesophiles were determined in accordance with the Mexican Norm NOM -092-SSA1-1994 and total coliforms in accordance with Mexican Norm NOM-113-SSA1-1994.

Analysis of results

In order to establish the perception of the concept of quality (in milk and cheese), the information obtained in the questionnaires was firstly analysed by means of a matrix. Later the observations in the collector journeys were contrasted to the laboratory results and the perception at the different chain links. The increment of milk’s temperature was grouped in quartiles so as to establish the characteristics of the collector’s handling, which complemented the information, obtained from the questionnaires and allowed establishing the role of the intermediary in quality.

The main variables taken into account were: quality control by each actor, quality demand, role or participation of each one in its improvement, the role regulations and official instances play in the fulfilment of quality, and finally the problems encountered at the chain level.

Descriptive statistics were used to analyse density, acidity, protein, total solids, water added to milk and pH and were compared to the values of the norm NMX-F-700-COFOCALEC-2004. A paired Student’s “t” test was utilized for initial and final sample values, with a significance level (p<0.05). The results of the total aerobic mesophiles and coliforms were compared to Mexican norms NOM -092-SSA1-1994 and NOM-113-SSA1-1994.

Results and discussion

Characteristics of recollection

Collectors transport milk from dairy farms, which do not have cooling tanks and are far from the cheese-makers (between 4 and 20 km), the transport is carried out by means of uncovered pick-up truck vehicles; milk is collected in 220-liter plastic drums; and collection begins at 6 or 7 in the morning and takes from 3 to 8 hours. In this area, similarly as that mentioned by Espinoza-Ortega et al (2007) and Cesín et al (2007), collectors’ function is fundamental as it is the link between dairy farms and cheese-makers.

The roads are mostly unpaved and in some cases improvised, therefore in the rainy season it is difficult for vehicles to move along it, which means that some farmers have to take their milk near to all weather roads, with an additional damage to the product’s quality. In this respect, Oyarzún (2002) mentions that the lack of roads and commercial infrastructure in developing countries is a factor that affects the development of rural agro-industries.

The concept of quality

In dry season there is milk scarcity, so that competition is increased among collectors to gather a higher volume; a time then when the farmers have capacity to choose whom they sell their milk to. The main factor determining sales is price, the one who pays best is the one who attracts more farmers and collects more litres. In the rainy season the opposite occurs, since there is more a larger offer of milk available, so that price declines.

Cheese-producers are who eventually establish the price, and demand the volume from collectors, regardless of how they acquire it. As a matter of fact they do not have any contact with the dairy farmers. They also demand unadulterated milk (without added water) and the absence of strange materials; however as they do not have any other demand they accept the unwritten rules disregarding the product’s quality (Table 1).

Table 1. Perception of the concept of quality in the milk-cheese chain

Dairy Farmer


Cheese producer

Unadulterated milk

No water added

Acceptable “acid” milk

Cattle feeding – good milk

Volume of litres delivered

No strange particles Unadulterated

As a result, established Mexican regulations are not met, in a large part due to ignorance of them by the actors in the milk – cheese chain. It is evident that nowhere in the chain is quality control applied, not even by the official instances that regulate quality.

Several authors mention that in order to establish the quality of any food, not only is it necessary to observe the innocuousness and safety technical aspects, but also to consider the social and cultural context in the zone so as to provide a “distinctive quality” for these products. Appedinni et al (2003) mention that quality must go beyond the product’s nutritious quality, as the quality of a given food is not the same for everyone, since it is constructed according to the particular problems of a place. Thereby, its conceptualization must be exclusive for the zone’s product or sub-product, letting the regulatory aspects on the local official instances, although sanitary aspects cannot be left aside.

At the level of Mexican regulation and official instances, in this case ISEM, they mention that in order to improve sanitary quality, the infrastructure of the cheese-producing agro-industry must be improved. Supervisory activities they commonly perform are: verification visits for facilities and equipment, and the hygienic practices of the personnel are observed to check on factors that might be vehicles for microbiological or physicochemical hazards in the product’s elaboration. However, they do not consider any aspect related to milk preservation along its production and transport. Cheese-producers mention that during inspection, ISEM officers never consider milk’s quality and only observe infrastructure, and as expected, neither do they consider milk in previous links. In this respect, this instance mentions that this task is out of its reach due to the lack of reliable information on farmers.

The establishment of a quality concept at local level for an alimentary product would need to institute a regulatory group or organizations that set, by means of a thorough diagnosis along the productive chain, which the characteristics of the product are and which the specific quality must meet. According to Oyarzún (2002) there are no quality seals to commercialize products at national level in Mexico; and it has been only as from 2001, and for exportation products, that there is the official brand: México, Calidad Selecta (Mexico: Selected Quality). This scheme was created with the aim of supporting the entrance of Mexican products into new markets and consolidating their presence in those where they are already commercialized; this is only applied at an international level, since in reality products that are locally elaborated are only recognized at regional level. However, they could lose this recognition if consumers started to ask for standards or quality seals.

This problem is reflected in the results from laboratory analysis.

Physicochemical and bacteriological evaluation of milk

The physicochemical variables met requirements from the Mexican regulation for raw milk (NMX-F-700-COFOCALEC-2004), which establishes three categories: A Class (protein > 31g/L, fat > 32g /L), B Class (protein from 20 to 30.9 g/L, fat < 31 g/L), and C Class (protein from 28 to 29.9 g/ L, fat < 30 g/L). All of the analysed samples met specifications for milk Class A, a situation that has also been reported in other works (Bernal-Martínez et al 2007). Where at dairy farms level perceives milk’s quality and yield in an empirical manner from the amounts of fat and protein, nevertheless it is mentioned that the main demand from collectors is that milk is not adulterated with added water. This was confirmed by the laboratory’s findings, as the milk produced in the zone meets this request from milk collectors, although the producers totally lack knowledge on the regulation’s requirements.

There were no statistically significant differences between the milk samples before or after transportation, thus indicating there was no deterioration attributable to transport (Table 2).

Table 2. Global physicochemical analyses of raw milk from initial and final samples


Maximum in Regulation





Fat (g/kg)







Protein (g/kg)







Density (g/kg)





















SNG (g/kg)







NS = P > 0.05

The increment in acidity is due to the fact that remains for several hours at ambient temperature, which accelerates the bacterial multiplication process, hence acidification. Although milk collectors notice this acidification, they do not demand anything from farmers, since they are not required anything in terms of milk acidity from the cheese-producers, and at present official instances do not regulate this. The main reason for this is that acid milk is utilised in the elaboration of “Oaxaca” type cheese.

The acidity found was superior to that established by the Mexican regulation. Nhuch (2008) establishes that values above 1.4 ºD indicate milk has suffered deterioration, which is explained by the lack of a cold chain (Chombo 1999).

Works carried out in the State of Jalisco in western Mexico, show that it is possible to change this apparent lack of concern for milk quality, by establishing a cold chain. This was achieved as a result from pressures exerted on farmers both from the local and national agroindustry to improve milk quality. In order to achieve this, there was a need for small-scale farmers to get organized. This means that both shared trust and the organization in itself were fundamental to achieve the improvement in their products quality (Cervantes et al 2001; Lara et al 2003).

Microbiological evaluation

In all the samples, numbers of coliforms and mesophiles surpassed permitted levels, and results were related to the acidity results (Bernal et al 2004; Bernal et al 2007); who mentions it as a consequence of the lack of hygiene during the milking and storing process that enriches the microbial flora and accelerates the acidification process.

Notwithstanding that acidity is a variable that indicates milk’s deterioration, paradoxically, cheese-producers from the zone prefer acid milk, specifically to elaborate Oaxaca cheese, since acidity accelerates the curdling process and gives the specific characteristics to the cheese. However, cheese-producers are aware of the implications of increased microbial counts, since they mention it has a shorter life on display.

A high number of colony formation units (cfu) /ml indicates that the milk’s sanitary condition is deficient. In accordance with Calderón (2007), the determination of the total aerobic mesophiles and coliforms allows detecting deficient hygienic practices on the raw material.

Micari (2002), Fox (2003), and Ruegg (2005) report work undertaken in the USA and Europe studying both intensive and traditional cheese making systems, where the causes for high bacterial counts are diverse, noting conditions at milking, the conditions at storing and collection, lack of a cold chain, and long times for milk collection; as well as not using adequate means for milk transportation.

The same has been mentioned by Mexican authors (Chombo 1999; Cesín et al 2007; Cuevas et al 2007 and Espinoza-Ortega et al 2007), who have identified that these small-scale dairy production systems have disadvantages of technological nature, as farmers do not have the infrastructure and advice to improve milk’s quality.

Also, high bacterial counts directly affect the consumer; and if the pollution levels surpass levels established by regulations, it is a public health issue that involves all of the actors of the chain (Magariños 2000).

Chombo (1999) reports that the introduction in the state of Jalisco of milk cooling vats has benefited large dairy industries located in the “ Los Altos de Jalisco” region, as it has allowed them extend the margin of time to transport, processing and marketing of the milk they buy from small-scale farmers. The result becomes a multiple benefit, with a positive final impact on the sanitary quality of the milk that arrives to the agro-industries, and consequently, benefits the consumer.

The results seemed to suggest that the milk collector does not have any effect on the milk’s quality, so it was decided to incorporate the temperature variable into the analysis (Table 3). The results show that in all of the analysed cases there was an increase in temperature superior to 5 °C, which surpasses the limits of NOM-024-ZOO-1995. When grouping collectors in quartiles by temperature change, clear differences in milk handling are observed.

Table 3. Temperature analysis of raw milk from initial and final samples and its relation with the handling characteristics in transport


Initial temperature at farm gate (0C)

increment at
final delivery (0C)



farms per

Volume Sold
per Farm





























Collectors in quartile 1 take a shorter time in their milk collection rounds since they buy milk from a smaller number of producers who deliver a larger volume of milk per farm. Larger farms consider milk production as their main activity, so they have better milking and storing practices, which is reflected in the lowest temperature at delivery (Cervantes et al 2001).

On the other hand, quartiles 3 and 4 show the highest increment in temperature of milk (6 and 11 °C, respectively). In both cases they collect (and mix) milk from the previous evening milking as well as freshly milked morning milk, and these collectors buy from a large number of small dairy farms so the milk rounds imply longer times. Moreover, these small dairy farms do not consider milk production as their main income generating activity so the milking and storing practices are deficient.

In addition, it was realised at the moment of taking samples and applying the questionnaires that many of these farmers do not know the milk collector very well. There are no trust relations, on the contrary, as it was observed that usually those farmers who sold from 2 to 6 litres/day, left there milk beside the road so that the collector did not reach their home.

An important factor that affects milk’s temperature is the material used to contain it. In this area, 100% of collectors utilize plastic drums. Ruegg (2005) mentions that this material favours the increase of temperature, since plastic is not an isolator. Milk temperature increases as the ambient temperature does. The Mexican regulation establishes that milk must be transported in wide mouth churns, with round cap, not storing one upon another, made of steel or galvanized sheet metal or any other non-porous material that allows easy washing and disinfection, before and after each product’s delivery. Taking the aforementioned in consideration, only one collector does the washing of the churns once a week with running water, the accumulation of whey at the bottom of the container was observed in the study, as well as minute dry-milk stains in the neck of the churn, because conditions are rudimentary and the established regulative requirements are far from being fulfilled in this sort of systems.

Despite the problem in the zone of study regarding the bad sanitary quality of milk, the responsibility is not only attributable to a single actor of the chain, but to all of the actors as a whole, in addition to the official instances in charge of enforcing the norms.

It is worth mentioning that another factor that affects this systems is that the regulating norms were elaborated for standardized products, whereas traditional products were not considered, and given their know-how, they hardly fulfil the legislation.


The milk that is transported in the area of study meets the requirements of the Mexican legislation for physicochemical variables, except for acidity, which is an indirect indicator of bacterial pollution.

In terms of microbiological quality, milk presented high counts of aerobic mesophiles and coliforms, and did not fulfil the Mexican legislation, as milk displayed high bacterial counts from the moment it was collected. The collectors’ practices contributed to the deterioration of the product, which can affect the final product, as the final destination is to elaborate “non-pasteurized” traditional fresh cheeses.


The authors would like to thank all those who took part in the project, the Instituto de Ciencias Agropecuarias y Rurales (ICAR) for the chemical analyses. This work was possible thanks to the funds from the Mexican National Council for Science and Technology ( Consejo Nacional de Ciencia y Tecnología - CONACYT) within project 2003-CO2-42498 “Competitiveness of the Dairy Chain in the Mexican Highlands: Problems and Development Alternatives”. We thanks to CONACYT, for providing the grant for Minerva Hidalgo-Milpa to be grateful to the council mexiquense of science and technology (COMECYT) for the scholarship to stimulate this study.


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Received 13 April 2015; Accepted 14 August 2015; Published 1 December 2015

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