Application of FMEA analysis in the short cheese supply chain

1 Dairy Institute, Autoput za Zagreb 3, 11070, Belgrade, Republic of Serbia, 2 Department of Food Safety and Quality Management, University of Belgrade – Faculty of Agriculture, Nemanjina 6, 11080, Belgrade, Republic of Serbia, 3 Department of Technology of Animal Products, University of Belgrade – Faculty of Agriculture, Nemanjina 6, 11080, Belgrade, Republic of Serbia, 4 AD Mlekara – Subotica, Tolminska 10, 24000 Subotica. *Corresponding author: Nada Šmigić, nadasmigic@agrif.bg.ac.rs


Introduction
FMEA is a "bottom up" quantitative evaluation of the risks, by which the risk is assessed as the product of multiplication of values determined for severity (S), detection (D) and frequency of occurrence (O) of possible failures. Establishing a critical value for the RPN determines the need for appropriate corrective action. After corrective measures have been applied, the values for O and D have to be re-evaluated, while the value of S remains unchanged (Djekic at al., 2018;Arvanitoyanis et al., 2007).The assessment of the severity (S) of a failure is a measure of the impact that a failure can have on the health of the consumer, the required quality of the product and/or legislation. Assessment of occurrence (O) determines the frequency of occurrence of a given failure, while detection (D) is a measure of the possibility of easier or more difficult detection of a given failure (Kurt and Özilgen, 2013). In this paper, FMEA methodology was used to determine the biological, chemical and physical failures that may occur during the farmhouse production of white brined cheese (short cheese supply chain) in Serbia.

Cheese supply chain
To apply FMEA methodology, a flow diagram was made for the production of white brined cheese production in farmhouse conditions and green market sale (short cheese supply chain, Figure 1). This was done according to Popovic-Vranjes (2015) and the authors' personal experience.

FMEA analysis
After the flow diagram was prepared, the potential failure modes were identified for each step, and the possible effects and causes of each failure mode were also identified. Afterwards, the risk level of each failure mode was assessed, and corrective actions to reduce and eliminate the potential failures were suggested. Finally, the risk level of the corrected design was recalculated.
To assess biological, chemical and physical failures, the values for occurrence (O), severity (S) and detection (D) in the manner shown in Table 1 were determined, according to Djekic et al. (2018). For each potential failure, the RPN was calculated using estimated values for O, S and D. A numerical ranking for values of O, S and D was established taking into consideration available literature data, epidemiological studies and our own expertise and knowledge. All co-authors of this study, as experts in the field, participated in ranking the risks, using the Delphi method to stimulate and synthesize the opinions of experts and achieve consensus (Heiko, 2012). There were no holdouts and consensus for each type of risk analysed was achieved. Also, all participants confirmed that all important food safety hazards had been included in each activity within cheese supply chains. Depending on the likelihood of occurrence, each failure was assigned with an O value in the range from 1 to 5. The highest O value represented the greatest probability the failure would occur. The possibility to detect the failure before it occurs and the seriousness of the failure were also ranked from 1 to 5, where the values increase as it becomes more difficult to detect the failure before occurring, or as the potential damage caused by the failure increases.
The calculation of RPN was based on the work of Kurt et al. (2013), and it included multiplication of the values of O, S and D. The maximum value for RPN that could be obtained was set at 125. A RNP value of 6 has been accepted as the critical limit, above which corrective measures need to be taken (5% of the maximum value with a statistical significance of 95%). The RPNs after the corrective actions were also recalculated.

Results and Discussion
White brined cheese refers to a large group of cheeses characterised by the name of the geographic area where they are produced. Although this group accounts for a large number of cheeses and, hence, great variety in their specific properties, their common characteristic is that they are matured in brine under anaerobic conditions. The most popular cheeses that belong to this group in Serbia include Sjenica Cheese, Zlatarski Cheese, Svrljiški Cheese, Serbian white cheese etc., while Greek Feta Cheese, Cypriot Haloumi, Egyptian Domiati, etc. are white cheeses known worldwide. Traditionally, these cheeses are made from cow, sheep or goat milk, or their mixtures. In the farmhouse production of white cheeses, raw milk is often used, giving the product specific sensory characteristics, due to the presence of indigenous microbiota (Popovic-Vranjes, 2015;Radulovic et al., 2011;Terzic-Vidojevic et al., 2006).
In this paper, Serbian white brined cheese, traditionally produced in Pomoravlje, is described as an example of farmhouse cheese and a general flow diagram showing its production steps is presented in Figure 1. This cheese is usually made from raw cow milk, which is heated to the required temperature (in summer 18-20°C, in winter 25-30°C), and at this temperature, rennet is added to the milk. After coagulation, which lasts for 4-6 h, the cheese curd is left in a strainer and hung to drain; this is followed by pressing the cheese curd with a board and a stone (the pressure should be 1-2 kg/1 kg of cheese curd). Drainage and pressing usually takes up to 24 hours. The drained cheese curd is cut into slices, sprinkled with dry salt and arranged in wooden buckets or plastic cans. Ripening is done under load and usually lasts for 2-3 weeks (Popovic-Vranjes, 2015). The characteristics of farmhouse white brined cheeses depend on the microbiological composition of raw milk, as the types of indigenous non-starter lactic acid bacteria (LAB) present in milk depend on the ecological characteristics of the  dojevic et al., 2007;Radulovic et al., 2011;Popovic-Vranjes, 2015).
FMEA analysis in the short cheese supply chain The identified failures in cheese production and distribution chains, the calculated RPN values, corrective measures that can be applied, as well as the recalculated values for RPNs are presented in Table 2.

Assessment of biological failures in the short cheese supply chain
Very high values for RPN were determined for biological failures in the short cheese supply chain ( Table 2). The highest values were determined for the milking step (total RPN for different biological failures=175), followed by cheese ripening step (RPN=132) and transportation of cheese by personal vehicle (RPN=110). The presence of pathogenic microorganisms in raw milk might indicate the animals' impaired health condition, but also inadequate hygienic milking conditions. Dairy products play a significant role in the occurrence of food-borne disease outbreaks, because raw milk can contain pathogens that might remain in the dairy products and consequently lead to food-borne diseases. Due to its composition (water content, neutral pH, nutrient content), milk is a suitable medium for microbial multiplication. The most commonly isolated pathogens from raw milk include Staphylococcus aureus, Streptococcus spp., Listeria monocytogenes, Campylobacter jejuni, Escherichia coli, etc. Special attention towards the legislation was given to the infectious diseases, brucellosis and tuberculosis (Oliver et al., 2005, Kurt et al., 2013, Le et al., 2014, Serbia, 2011. Some of these microbiological hazards can be controlled at the primary production level (e.g. tuberculosis, brucellosis), while Listeria monocytogenes is much more widespread in the environment and the introduction of this bacterium into dairies can result in product contamination, biofilm formation, etc. (Oliver et al.,2005;Kurt et al., 2013;Le et al., 2014;Shirani et al., 2015). Legislation foresees the conditions that raw milk should meet in terms of total number of microorganisms and somatic cell counts (Serbia, 2010a;Serbia, 2011;Serbia, 2017b;Serbia, 2017c;Serbia, 2019). Application of good breeding practice and good veterinary practice, utilisation of animal feed from verified suppliers, education of owners and breeders of animals, who are often also the cheese producers in farmhouse production conditions, and application of legally determined norms could be used as corrective actions to control some biological failures in this cheese chain. By applying the proposed corrective measures, the recalculated RPNs values were reduced (Table 2).
Farmhouse cheese production, from the aspect of using raw milk that has not undergone any thermal treatment (Figure 1), carries the risk of causing food-borne diseases (Mauropoulos et al., 1999;Oliver et al., 2005). However, the controlled processes of coagulation and ripening of cheeses, due to the action of naturally occurring LAB, can still result in a product that is recognized as safe. Namely, LAB activity leads to a decrease in pH, and in conjunction with other factors such as storage temperature, salt concentration and water activity (a w ), might be limiting to the survival and multiplication of pathogenic microorganisms. In addition to this, LAB also produce antimicrobial substances such as bacteriocins, hydrogen peroxide, fatty acids, diacetyl, bacterio cin -like molecules, etc. (Mauropoulos et al., 1999;Bintsis et al., 2002;Terzic-Vidojevic et al., 2006;Veskovic-Moracanin et al., 2007;Bulajic et al., 2017).  Cheese production must be done in registered households Cheese production in the household can only be done from milk produced in that household (Serbia, 2017c) Milking animals must be covered by the program of measures and that the conditions for the production of raw milk and milk should meet the legal requirements (Serbia, 2011a) 2 5 5 50 Contamination with pathogenic microorganisms in milk equipment due to: ▪ usage of contaminated water for washing dishes (i.e. buckets) ▪ faulty washing / milk trapping ▪ poor storage conditions of washed equipment 2 5 5 50 Water quality should be periodically controlled Disinfection of containers must be done Washing the equipment must be complete The storage room for milk-contacted equipment must be kept clean and protected from pests 1 5 5 25 Contamination with pathogenic microorganisms due to impaired health of the person handling raw milk 2 3 5 30 Intermittent sanitary inspections must be done Education of farmers / persons handling raw milk is recommended Maintaining personal hygiene is essential People with signs of illness are not allowed to work with food 1 3 5 15 Psychrotrophic microorganisms present in raw milk (spoilage microorganisms) and their possible outgrowth during cooling 2 2 5 20 Adequate temperature 1 2 5 10

Addition of coagulants
Contamination with pathogenic microorganisms due to impaired health of the food handler / cheese producer 2 3 5 30 Intermittent sanitary inspections must be done Education of cheese producers is recommended Maintaining personal hygiene is essential People with signs of illness are not allowed to work with food Microbial contamination of water for making brine solution 2 5 5 50 Visual inspection of brine must be done Potable water is recommended to be used 1 5 5 25 Growth of pathogens and spoilage microorganisms due to inadequate pre-requisite for cheese ripening room (temperature, room hygiene, room humidity, air flow) 2 5 5 50 The ripening of cheese must take place under controlled conditions The ripening room must be tide and clean The temperature in the maturation room should be below 18°C

Milking
The presence of residues of veterinary medicine drugs (antibiotics, hormones, growth stimulants) due to non-compliance with the prescribed withdrawal period 3 3 5 45 Veterinary medicines should be given only according to the instructions of the veterinarian 1 3 5 15 The presence of aflatoxins in raw milk due to poor agricultural practices (animal feed) 3 3 5 45 Good agricultural practice must be performed Animal nutrition should be done by commercial feed from verified suppliers (authorized animal feed sales) 2 3 5 30 The presence of chemical contaminants (pesticides, dioxins, organophosphates, etc.) in raw milk due to poor agricultural practices (animal feed) 2 3 5 30 Good agricultural practice must be performed Animal nutrition should be done by commercial feed from verified suppliers (authorized animal feed sales) 1 3 5 15 The presence of detergents and disinfectants in raw milk collection equipment due to improper washing and rinsing 2 2 5 20 Using of approved agents for washing and disinfection according to the manufacturer's instructions, good rinsing must be done Chemical contamination of the water used to make brine with heavy metals and / or residues of the chlorine 2 3 5 30 Water quality testing must be done regularly Potable water is recommended to be used 1 3 5 15 Direct sale (open market) Residues of detergents for dishwashing 2 3 5 30 Approved detergents and disinfectants must be used Good rinsing after washing must be done Disinfectants must be used according to the manufacturer's instruction 1 3 5 15 Chemical contamination due to utensils (dishes, knives, etc.) 2 2 5 20 Materials that are allowed in the food industry must be used Equipment that can be easily maintained and where necessary disinfected (e.g. stainless steel) must be used 1 2 5 10 Chemical contamination due to inadequate material used to cover the bowl (wood, rusted lids, newspapers, rags) 2 2 5 20 Plastic lids or / and foil may be used 1 2 5 10 During coagulation and whey drainage, pH should decrease to a value of 4.6 or lower. Syneresis and salt addition decreases the a w , which slows the growth of pathogenic microorganisms, and affects the cheese structure, enzymatic activity, etc. (Pacheco et al., 2010;Bulajic et al., 2017). In household production, the key moment is the visual inspection of whey, when the appearance of clear, light green whey with a pleasant taste and smell indicates the milk has coagulated well (Popovic-Vranjes, 2015). If changes in whey colour, a sour taste of curd or unpleasant smell occur, the production must be stopped and all Production, processing and marketing phase

Milking
The presence of foreign bodies originating from damaged equipment (pieces of metal, strand wire, cloth parts, etc. ) 2 4 2 16 Equipment made of adequate materials must be used Damaged utensils must be replaced Raw milk filtration must be done 1 4 2 8 The presence of straw / litter, hairs, mud, insects, rodent faces, etc. due to poor hygiene and breeding practices and / or machine milk due to the fall of suction cups on the ground 2 3 2 12 Good hygiene and breeding practices must be applied Protection of raw milk from pest must be done Filtration of raw milk must be done 1 3 2 6 The presence of foreign bodies originating from a person handling raw milk (buttons, jewelry, etc. ) 2 4 1 8 Good hygiene and manufacturing practice Education of farmers / persons handling raw milk is recommended 1 4 1 4

Coagulation
The presence of foreign bodies such as insects, larvae, glass, metal parts, hair) in utensils 2 3 2 12 Manipulation of glass materials must be avoided Protection of utensil from insects and other pests must be done Personal hygiene is required 1 3 2 6 Curd treatment The presence of foreign bodies originating from the person who cuts curd into slices (hair, buttons, jewelry) 2 4 1 8 Personal hygiene must be regular 1 4 1 4

Salting
The presence of foreign bodies in salt 2 3 1 6 Salt must be obtained from registered stores 1 3 1 3

Transport
The presence of foreign bodies (glass, metal parts, hair, dust, insects, insect larvae, etc.) due to poor vehicle hygiene 2 3 2 12 Regular maintenance of vehicle hygiene must be done Transport in closed containers is recommended Regular cleaning and disinfection must be done 1 3 2 6 Direct sale (open market) Physical contamination due to cheese exposure in open dishes 2 3 1 6 It is recommended that the cheese is sold at open markets in sealed containers, as well as during the sale remains covered with plastic foil 1 3 1 3 Contamination due to the presence of metal particles originating from damaged dishes or other equipment (e.g. knives) 2 5 2 20 Cheese in which the presence of metallic particles has been determined must be removed and destroyed Damaged and broken equipment must be replaced 1 5 2 10 Physical contamination due to touching the product by the customers or sellers (hair) 2 2 2 8 Disposable accessories should be used (toothpicks, plastic clip, cardboard coasters) 1 2 2 4 Physical contamination due to accidental breakage of glass bottles or glasses 2 4 1 8 Cheese in which the presence of glass has been established should be destroyed and removed Handling with glass near food should be avoided 1 4 1 4 obtained curd and whey must be discarded (Serbia, 2019;Olofson, 2010). In farmhouse cheese production, most of the steps involve manual manipulations, such as milking, rennet addition, gel cutting, salting and stacking in buckets (Figure 1). In addition, during cheese sale at the green markets, manual manipulation is inevitable. Therefore, it is clear that the cheese producers' personal hygiene is very important. Legislation in Serbia determines the conditions that persons involved in food production must meet in terms of maintaining personal hygiene and wearing of appropriate and clean protective clothing. Food handlers must not suffer from food-borne diseases, must not have infected wounds, skin infections and injuries or diarrhoea, and food handlers are obligated to report illnesses or symptoms. For persons who perform activities involving direct contact with food, the legislator mandates health examinations twice a year. Hand hygiene of persons handling food must be maintained, which is achieved by installing a sufficient number of hand washing stations with hot and cold water, hand washing agents and suitable disinfectants (Serbia, 2010a;Serbia, 2011;Kurt et al., 2013;Serbia, 2017).
In farmhouse cheese production, it is essential the production steps of coagulation, gel cutting, whey drainage, salting and stacking in buckets take place in clean environments. Identical hygienic conditions must be met in both industrial production and distribution in retail chains. In farmhouse cheese production, the washing step is usually performed manually, while in industrial facilities, automatic cleaning in place (CIP) technology is applied. The utensils should be washed as soon as possible after the production of cheese, but the washing step must not be performed during the production process. In order to preserve the desirable microbiota in farmhouse conditions, mechanical cleaning and washing of surfaces is recommended, but not the use of disinfectants. In such conditions, special attention should be paid to the mechanical cleaning of cheese making equipment, the appropriate water temperature and detergent concentration, as well as the washing time (Olofson, 2010).
Untimely and inadequate washing of equipment used in household cheese production can result in microbiological contamination, due to retention of milk and gel that remain from previous production. We rated this failure as RPN=30. This failure could also be seen through the possibility of biofilm formation. Namely, the occurrence of biofilms on materials used for the food production (stainless steel, plastic, glass, etc.) and from which kitchen equipment used in households is also made, is described in the literature (Olofson, 2010;Giaouris et al., 2012;Moretro et al., 2004;Katic, 1995). The possibility of this phenomenon in farmhouse cheese production should not be neglected. Although special attention is paid to pathogenic microorganisms such as Salmonella spp., Listeria monocytogenes and Staphylococcus aureus, the occurrence of LAB biofilms has also been described, in which pathogens have been identified.
According to Serbian legislation (Serbia, 2017), the mandatory data the small producer must state on the food label are name and address of the manufacturer, production date, product name, shelf life, storage conditions and household registration number. The shelf life of farmhouse white cheeses, and therefore their quality and safety parameters, is dependent on many different factors, including composition, degree of maturity, storage conditions etc. According to Popovic-Vranjes (2015), white brined cheeses matured for 2-3 weeks might be stored for months. However, when the maturation period is shorter in order to produce fresh cheeses, the subsequent shelf life is also shorter. The production of these cheeses is based on the tradition and experience that generations of housewives have gained. Passing the experience from generation to generation has contributed to the preservation of this traditional production. According to the Serbian legislation (Serbia, 2010b), cheeses can be divided into the following categories: extra hard cheeses with a ripening period that must not be shorter than 6 months, hard cheeses that must ripen for at least 5 weeks, semi-hard cheeses that ripen for at least 2 weeks and soft cheeses that ripen for at least 7 days. Depending on the length of the ripening period, the shelf life of these cheeses also changes, as a longer ripening period is associated with a longer shelf life due to microbiological and biochemical changes that characterise the ripening period and by which the desired sensory and textural characteristics are achieved. Fresh cheeses are characterised by low dry matter content with a consequently high a w , and low fat and protein contents but a high lactose content, which makes them perishable foods (they can remain unspoiled for only a few days). On the contrary, in ripened cheeses, dry matter, fat and protein contents are higher, but lactose and water contents are lower, which prolong their shelf life (Pacheco et al., 2010). Questions remain as to how long the shelf life is of farmhouse-produced cheeses that are sold at green markets in Serbia, and how should the small producers determine the shelf life of their cheeses. Chemical failures can be identified at all stages of farmhouse cheese production and distribution. The main chemical risks we associated with raw milk were the presence of aflatoxins and antibiotic residues, as a consequence of poor breeding practices and veterinary malpractice, respectively. The highest RPNs were determined for the presence of antibiotic residues and aflatoxin contamination in raw milk. In farmhouse conditions, RPN values were rated as 45, 45 and 30 for antibiotic residue, aflatoxin and chemical contamination, respectively. The occurrence of pharmacologically active substances in food of animal origin is most often caused by the use of veterinary drugs used in the treatment of dairy animals. Residues of veterinary medicinal products are classified in group B of chemicals that can be found in food (according to Annex I of Council Directive 96/23/EC), where environmental contaminants are also present. Here, the greatest importance is given to antibiotics, which are relatively stable at pasteurisation temperatures, but also at low temperatures.
The influence of antibiotics in cheese production can be divided into two areas: 1) influence on consumer health (hypersensitivity reactions, development of antibiotic resistance in pathogenic microorganisms, changes in digestive tract microbiota) and ; 2) influence on cheese production (inhibition of LAB, delay in achievement of the appropriate pH, as well as altered sensory characteristics and possible growth of pathogenic microorganisms due to inadequate LAB activity) (Marth et al., 1959;Albright et al., 1961;Kurt et al., 2013, Katic & Bulajic, 2018. Farmhouse cheeses are made of milk that is produced in that household (Serbia, 2017). The presence of antibiotics in milk can be prevented by applying good breeding practices, regular health checks of dairy animals according to legislation (Serbia, 2005) and by educating the breeder, who is also the cheese producer, to respect the prescribed withdrawal period.
Mycotoxins are secondary metabolites of fungi that reach the milk via contaminated animal feed. In dairy farming, the highest importance is attached to aflatoxin M1. Aflatoxin M1 is excreted by cows into raw milk, is resistant to heat treatment and due to its binding to casein micelles in cheese, it occurs in higher concentrations in cheese than in the milk from which the cheese is produced. Usually the concentration increase (from milk to cheese) ranges from 3-fold in soft cheeses to 5-fold in hard cheeses. Cheese is considered to be the most important source of aflatoxin M1 among all dairy products (Ardic et al., 2009;Skrbic et al., 2014;Kos et al., 2014;Polovinski-Horvatovic et al., 2009;Tomasevic et al., 2015;Miocinovic et al., 2016). At this point, the control of aflatoxin M1 in farmhouse cheese production is questionable, because no controls of aflatoxin in raw milk are performed at the household level. Aflatoxin M1 in milk originates from animal feed. Therefore, application of good agricultural practice, with special attention to the conditions of storage of animal feed, and good breeding practices are considered as suitable corrective measures.
Chemical contamination resulting from non--compliance with hygiene standards (presence of residues of detergents and disinfectants, inappropriate materials from which equipment is made, etc.) can be prevented by educating individual producers, by applying good manufacturing practices and using permitted means of hygiene and disinfection at all stages of production and trade (Table 2). Also, water used on food production farms must meet the requirements for potable water, regardless of whether it is used from the public supply system of consumers or from their own wells (Serbia, 2010a;Serbia, 2017).

Assessment of physical failures in the short cheese supply chain
An artefact is defined as any unwanted object in food that originates from the food itself (intrinsic such as bones in meat products, fruit seeds, etc.) or originates from other sources (extrinsic such as glass, plastic, metal parts). The presence of artefacts in food can cause serious consequences (oral cavity injuries, suffocation, damage to the digestive tract, internal bleeding and even death). The most common injuries recorded as a result of ingestion of artefacts were caused by sharp metal objects (parts of equipment, wires, etc.), but such dangers can be caused by other types of artefacts such as jewellery, artificial nails, pieces of wood, etc. (Trafialek et al., 2016). Metal artefacts can be present in cheese due to contamination of raw milk because of poor milking hygiene or can occur during the different production steps as presented in Table 2.
The RPN value calculated for the identified physical failures (116) was significantly lower than those obtained for chemical and biological failures (390 and 741, respectively). The short cheese supply chain consists of a series of manual processes from production to sale, which can result in the occurrence of artefacts in the product (from hair that can lead to consumers' nausea, to metal parts that can lead to injuries). The application of appropriate hygienic conditions during the production, transport and trade of cheese at the markets as well as the education of individual producers are considered as appropriate corrective measures. The highest value for physical defects was determined for the presence of metal foreign bodies originating from damaged equipment during sale at the green markets (RPN=20). Destroying suspect products and replacing damaged equipment are considered good corrective measures to reduce the RPN to 10.

Conclusion
In this paper, FMEA methodology was used to quantitatively determine the risks that can be observed in different phases of white brined cheese production and trade in a short supply chain (farmhouse-produced cheese which is sold at green markets). Our results indicate the greatest risks in the short cheese supply chain can be attributed to biological and chemical failures, due to any failures being unlikely to be detected by cheese producers and having severe consequences. The proposed corrective measures include different pre-requisite programs. Even the application of these measures will not result in great risk reduction, as the severity and detection will remain the same. Small cheese producers on their own initiative rarely send cheese for the external analysis, as this is most often done by competent authority during regular controls. Therefore, the biological and chemical failures are usually not detected at all in farmhouse cheese production. To increase detection and consequently to decrease the risk, some rapid hygiene monitoring techniques such as ATP (detection of adenosine triphosphate by bioluminescence) and protein kits might be used. They are designed to provide rapid results and to be used by unskilled personnel, such as cheese producers, to assess the effectiveness of their cleaning procedures. This might be supported and organised by government institutions. At the same time, this conclusion cannot be applied to physical defects because they are visible and, therefore, easier to detect, which is indicated by the relatively low RPN values for these faults calculated in this study.