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2.7. Managing production and quality assurance

2.7.1. Managing production
2.7.2. Managing quality assurance

2.7.1. Managing production

Production planning
Scheduling inputs
Staff management
Health and safety

The design of the processing operation is selected during preparation of the Feasibility Study (Section 2.3.3). Once equipment and facilities are in place, it is then necessary to organise staff for routine daily production. This involves five basic components: production planning, scheduling of inputs, maintenance, staff management and health and safety. These are described below, followed by details of quality assurance procedures needed to prepare quality specifications and to maintain product quality during routine production.

Production planning

The planning techniques that are described in Section 2.3.3 for preparation of feasibility studies are used in a modified way on a daily or weekly basis to plan the activities of the enterprise. The first step is to estimate the likely demand for the products and then use this to plan the amount of production to be undertaken. However, instead of demand estimates arising from market surveys, as in the feasibility studies, the entrepreneur has more up to date information from knowledge of current sales. Among the records kept by a business (Section 2.9), there should be a sales book that details the amount of product sold each day. The book may also record where sales were made and to whom. By adding the daily sales figures to form monthly totals, it is possible to produce a sales graph (Figure 50) that shows the trends in sales for each type of product. From this the owner can then estimate the likely scale of production that will be needed each day or each week to meet the expected sales.

Figure 50. - Example of sales trends for two products

In the example given in Figure 50, sales of lime pickle are predictable, having climbed steadily to 180 kg/month. Sales of mixed pickle were lower at just over 100 kg/month before a promotion in May which resulted in an increase to 140 kg/month. In this example, the sales trend is likely to continue at these levels and the volume of production can therefore be planned at 9 kg/day of lime pickle and 7 kg/day of mixed pickle, assuming that there are 20 working days per month. In practice, it may be worthwhile increasing the production rate to 12 and 10 kg/day respectively, to take account of delays in processing through electricity failures, lost working days etc. and to build up a small stock of product. If further promotions are planned it is necessary to increase production beforehand to meet the anticipated increase in demand.

Scheduling inputs

Having decided on the level of production that is needed to meet anticipated sales for the next week or month, it is then necessary to schedule all of the inputs that will be needed to produce the required amount of product. These include not only the components of the products, (raw materials, ingredients, packaging, labels, distribution cartons etc.) but also the number of staff required (especially if they are hired on a daily or weekly basis), cleaning materials, water requirements etc.

With knowledge of the formulation that is used to make each product, the weights of each ingredient and the number of packages that will be required can be calculated. After consulting records of the stocks that are held in store (see Section 2.9.2), orders can then be placed with suppliers to maintain the required levels of inputs.

A common failure of small fruit and vegetable processors is inadequate production planning, so that production ceases midway through a day because for example, one ingredient is used up or the supply of labels or bottle caps is finished. In most developing countries, unless a processor is located near to a large town, it is difficult to quickly replace ingredients or packaging materials and this results in substantially reduced output from the unit. Attention to production planning is therefore crucial to maintain production levels at the planned capacity.

In the author's experience, operation at a small percentage of the planned capacity is one of the most common reasons for failure of an enterprise. This is particularly the case when fixed costs are a relatively large proportion of total costs and the business simply does not produce sufficient product or generate sufficient income to operate above the breakeven point (see Section 2.3.4). In other businesses, the shortfall in production resulting from delays in processing caused by missing inputs, means that the cashflow is inadequate to pay bills, the producer reaches credit limits with suppliers, who eventually refuse to provide inputs.

Because of the difficulties in obtaining ingredients and especially packaging materials in most developing countries, processors are forced to buy larger amounts of stock to protect themselves against intermittent and unreliable supplies. This causes cashflow difficulties both because of the large expenditure to buy the materials and because the cash is tied up for many weeks while stock is waiting to be used.

The alternative of buying inputs more regularly in smaller quantities is often favoured by smaller enterprises to overcome the cashflow problem, but this is not really a solution because items bought in this way are more expensive than buying in bulk and as described above, the risk of loss of production due to intermittent supply is greater. Small businesses are therefore caught in a dilemma of risking a negative cashflow or suffering disruption to production. The problem can be partly addressed by adequate initial financing of the enterprise, perhaps with the facility to take a loan in phases over several months to meet the shortfall in finances caused by periodic negative cashflow (see also Section 2.3.4).

A further difficulty for fruit and vegetable processors, that is less of a problem for other types of enterprise, is the relatively short harvest season for the majority of raw materials. This has three effects: it means that the majority of raw materials must be bought and paid for in a short space of time; where intermediate (or part-processed) products are made, the cash in a business is tied up in part-processed materials for long periods; and when a succession of fruits and vegetables are processed throughout the year, this increases the complexity of production planning because a large number of different ingredients and packaging materials need to be ordered in advance.


Another common reason for lost production is delays caused by equipment breakdowns and waiting for spare parts. Most small scale producers do not have a stock of spare parts for equipment used in their processes, citing the cost as a reason. Equally however, few producers have compared the cost of a stock of spares with the cost of delayed production. This is especially important when equipment has been imported and suppliers of spare parts are not easily contactable, or delivery times are several weeks.

In most enterprises, there are a few items of equipment that are likely to wear out more quickly than others. These include blades in preparation equipment, bearings on motorised mixers, fillers, dryer fans and heating elements in bag sealers. The entrepreneur should therefore identify the specific items of equipment that are likely to fail most often and ensure that a spare component is always kept in stock. Electric motors can be re-wound by small electrical contractors in most urban centres and an arrangement should be made in advance that they will repair equipment as a priority, if the processor guarantees that all such work will be handled by them.

Most small scale processors do not have a programme of planned maintenance of equipment and facilities, preferring to rely on the maxim 'if it is not broken, don't fix it'. There are differences in opinion among engineers over the benefits of a planned maintenance programme. Some believe that it is cheaper to allow equipment to break down and then repair it, whereas others consider that it is cheaper to stop production on a regular basis and replace parts before they wear out. It is likely that the costs and benefits of planned maintenance depend on the speed at which repairs can be done and the value of the spares that have to be held in stock and this is different for every enterprise. As a minimum, managers should monitor the state of equipment and facilities that are likely to wear out and as experience of the rate of failure accumulates over the years, they should buy spare parts or send the machine for servicing at the time the next replacement is anticipated.

Staff management

It is not possible in a book of this type to detail the different features of successful personnel management, but an outline of the principles on which an owner or manager can provide fair and reasonable working conditions for staff is described below.

One aim of a manager should be to ensure that all staff understand the nature of the business and are active in working towards its success. This is particularly important in relation to quality assurance (below) which requires all staff to agree quality management procedures and as individuals, to routinely monitor product quality.

If it is accepted that most people wish to have the following aspects in their job, the manager can arrange work to meet these needs:

· a reasonable wage
· security of employment
· a feeling of belonging to the company
· respect for their skills and knowledge
· good relationships with other staff
· opportunity to develop new capabilities
· reasonable working conditions.

The level of salaries that are paid to processing staff in the majority of small enterprises is usually slightly higher than equivalent work in the Public Sector, to take account of the lack of job security compared to government jobs. However, in many areas where there is substantial unemployment, wage levels are forced down. While any entrepreneur may wish to reduce production costs as much as possible, paying staff below the market rate for a particular job is short-sighted. Trained and experienced process workers are an asset to a small enterprise because they are able to produce products efficiently and to a consistently high quality with minimum supervision. If salaries are too low, workers will seek alternative employment as soon as the opportunity arises, and the expenditure on training and developing their skills will be lost.

The terms and conditions under which staff are employed vary widely in developing countries and in many cases they are employed on a casual basis with no formal contracts or even letters of appointment. In small enterprises, this situation is not likely to change unless governments or other agencies press for changes. However, it is in the entrepreneurs' own interests to create a working environment in which staff members feel that they have security of employment, because they are then more likely to actively work to improve and develop the business. One example of the way that staff feelings of belonging to and sharing in a business could be encouraged is a simple outline of the benefits that they can expect in terms of breaks for meals, amount of pay for sickness or holidays, terms under which absence from work is acceptable (for example for bereavement) etc.

The majority of people wish to have their skills and knowledge recognised and to be able to develop these further in their work. Managers of small enterprises have the opportunity to know the relatively few staff better than in large companies and it is their responsibility to find out what are the skills and aspirations of each worker. Again, it is in the managers' own interests to do this because each worker's skills can then be used most effectively for the benefit of the enterprise. In practice, this may mean allocating specific areas of responsibility, such as record keeping, labelling of products, raw material inspection etc. to those staff that have an aptitude for that type of work. However, it is also necessary to train staff in every aspect of production, regardless of their main area of expertise. When all staff know how to do every job in a production unit, there are opportunities for people to do different work during the day (for example in Figure 33) leading to greater job satisfaction and greater flexibility in job allocation to cover for staff absences.

The owner or manager is responsible for providing reasonable working conditions for employees. This is covered by law in some countries, although it may be infrequently enforced (see also Section 2.4.2). As a minimum, the requirements for hand washing and toilet facilities should be met for both workers' benefits and to maintain hygienic production. Preparation tables should be high enough for staff to work comfortably and where repetitive work is carried out for long periods, as for example in manual packaging and labelling, seats and good lighting should be provided. The owner may also consider providing a rest area with cold water and seating, to prevent workers sitting on stocks of packaging or finished product as the only comfortable place to take a break. These benefits are important to retain experienced staff and contribute to the overall efficiency of production.

Figure 51.- Trained and experienced workers are an asset to a small enterprise

Health and safety

The provision of facilities for staff are important for improved efficiency and staff morale, but the entrepreneur also has a responsibility to staff to provide a safe and healthy working environment. In some countries, this is a legal requirement, but even if legislation does not exist, the consequences of accidents and illness arising from poor working conditions are far greater than any difficulty in ensuring safety.

Most types of fruit and vegetable processing are inherently safer and healthier than some other types of work, such as mining or driving. However, there are dangers in processes that involve heating, particularly when large containers of viscous products such as jam or sauce have to be handled at boiling temperatures. The manager should therefore provide aprons and heat resistant gloves and also train staff to handle such foods safely.

When workers are preparing fruit over several hours, they should be provided with thin gloves to prevent skin damage from fruit acids. This is especially the case with pineapples, which contain an enzyme that attacks skin.

There are also dangers from sharp blades when preparing fruits and vegetables, particularly when motorised cutters or liquidisers are used. Again, it is the responsibility of the owner or manager to ensure that proper training in the correct procedures is given and attention is paid to ensuring that fail-safe devices such as electrical cut-out switches are operational. On larger equipment that is powered by drive belts, there should always be guards in place, staff should be trained to understand safe operating procedures, particularly when cleaning such equipment. The manager should also enforce dress codes to prevent operators from wearing clothes or jewellery that could become entangled in moving equipment.

Dust production is a problem in a few processes and in others the heat and steam produced from boiling pans can produce an unhealthy working environment. The manager should take the necessary steps to extract these from the plant and provide adequate lighting and ventilation to maintain a healthy workplace (see also Section 2.5.3).

2.7.2. Managing quality assurance

Safety of products
Product quality
Raw materials and ingredients
Packaging, storage and distribution
Hygiene and sanitation

When a new enterprise is established it is necessary to both standardise the quality of fruit and vegetable products and also ensure that they are safe to eat. The owner should work with the staff to go through each stage of processing, from purchase of raw materials and ingredients to the consumption of the final product, to identify where factors exist that could influence either product quality or safety and to then devise procedures that control those factors. This is known as developing a Quality Assurance System.

Implementation of this system starts with processors deciding which focus to address first: improvements to product quality or improvements to product safety. They then examine every stage in the process to find where improvements can be made. If safety is the main reason for doing an analysis, the aim is to draw attention to potential risks and then develop measures to monitor and control the risks so that they do not become a hazard.

Safety of products

Although fruit and vegetable products have a lower risk of food poisoning than for example meat and dairy products, they can still become contaminated with potentially hazardous materials and quality assurance should be an essential component of production planning. In most developing countries, the requirement to produce safe foods in a hygienic way is part of the law and there are serious penalties for those who contravene hygiene and food safety legislation (Section 2.4.2).

The safety of fruit and vegetable products can be assured by implementation of a management method known as the Hazard Analysis Critical Control Point (HACCP) system. This is designed to prevent problems from arising, rather than curing them. In essence, the process of implementing HACCP systems involves the following stages:

· identify potential hazards
· assess the level of risk
· design and implement procedures for
· monitoring and controlling hazards
· apply corrective action in a process
· train all staff in implementation of the procedures
· develop appropriate reporting procedures.

Many small processors may think that development of HACCP systems is not necessary or not possible because it will either be too difficult or too expensive for them. However, in many developing countries HACCP is no longer a choice but is being demanded by the local Bureau of Standards or by companies that import processed fruits and vegetables. Greater awareness by consumers about food safety and their requirements for improved quality are likely to result in universal implementation of basic HACCP systems in most countries. However, to develop a system, most small scale processors need assistance and advice from professional advisers, including staff at a Bureau of Standards or a university who have experience of the product and the process.

This is especially true when an entrepreneur establishes a system for the first time. This type of assistance is also increasingly seen as a vital service that can be provided by Manufacturers' Associations.

Where an analysis of food safety is required, the stages identified above are implemented as follows:

Identify potential hazards and assess the level of risk: the processing stages are written out as a Process Chart (see Section 2.2 for examples) and ways in which contaminants could enter the food are identified. A selection of different types of contaminant is shown in Table 26.

Table 26. - Some types of contaminants in foods

Types of contaminant



Bacteria, moulds, yeasts, viruses


Hair, excreta, bone splinters


Pesticide residues, detergents


Bolts from machinery, stones, glass

Up to 95% of customer complaints in countries where these have been monitored, are related to contamination by physical, chemical or biological sources. Microbial contamination is therefore a small part of the risk, but in low-acid foods, the risk of serious food poisoning means that proportionately greater attention is given to this source.

During development of a safety system, emphasis should be placed on

· sources of contamination
· methods of contamination
· effect of the process on levels of contamination
· probability of micro-organisms surviving the process
· and growing in the product.

It is better to first select the most important type of hazard for a particular product and do the study for this. Potentially less important hazards can then be examined later and added to the quality assurance plan. An example of potential hazards and their level of risk in sauce production is shown in Figure 52. Following identification of hazards, the effect of processing conditions on contaminating micro-organisms is then assessed. This should include all parts of the process, from the purchase of raw materials and ingredients to storage and consumption of the final product. Examples of factors that should be examined in a process are the formulation of ingredients, particularly any that are likely to be heavily contaminated, the types of micro-organisms that may contaminate the raw materials, the pH or moisture content of the product and any preservatives that are used. This information is then added to the process chart (Figure 52).

Design and implement monitoring and control procedures: Once the range of potential hazards are identified, control methods can then be developed to prevent contamination. Some parts of a process have greater effect on product safety than others do. Where an error at a particular stage could have an important effect on safety, controls are put in place at these stages. These are known as Critical Control Points (or CCPs).

Figure 52. - Process chart showing potential hazards in sauce production

Stages in process

Potential hazards

Level of risk and measures to address risks




Mouldy fruit, contamination with soil, leaves, etc.

High risk: mould contamination could affect flavour and shelf life of product. Moderate risk: extraneous matter such as insects could contaminate product if not removed during inspection. Low risk: cosmetic faults in fruit, other contaminants that would be removed later in the process.

CCPs - no mouldy fruit or insect contamination.


Seeds and skins not removed

CCP - no peel or seeds in product.



Contamination of spices with dust, moulds, bacteria or foreign bodies. Correct pH of mixture

High risk: shelf life depends on correct mixture of acid, salt and sugar. Ingredient weight should be checked. Moderate risk: contamination of spices. Remove mouldy items and other contaminants during inspection and washing.
High risk: incorrect pH. Product depends on in part on acidity for preservation. Check pH.

CCPs - correct ingredient weights (Figure 17) +/-5%, correct pH +/- 0.2 units, no mouldy or contaminated spices.


Insufficient heating

High risk: adequate heating needed to destroy enzymes and contaminating micro-organisms and produce required consistency in product. Check time and temperature of heating.

CCP - heating at 100°C for 20 minutes +/- 5 minutes.


Faults in glass. Inadequate seal.

High risk: faults in glass could injure consumers. Check by 100% inspection of bottles. High risk: fault seal on cap could allow re-contamination. Check caps are correctly sealed.

CCP - no glass faults.
CCP - no faulty cap seals.


High risk: inadequate pasteurization results in spoilage during storage.

CCP - pasteurize at 88°C +/- 2°C for 20 minutes +/- 1 minute.



A 'Decision Tree' (Figure 53) can be used to help decide on the CCPs. Target limits and tolerances are decided for each CCP as shown in the example for sauce production in Figure 52.

Train staff to implement procedures: Staff are trained to operate the quality assurance methods. They should also know the limits that are placed on any variation from the specified methods, so that everyone involved in the process understands his or her responsibilities.

Develop reporting procedures: Methods for monitoring quality assurance procedures are designed, together with a plan of what should be done if the tolerances are exceeded. It should be clear who has the authority to make decisions and who is responsible for checking that a corrective action was properly done. This process is not just the responsibility of the owner or manager and it should be developed with the process workers so that everyone is clear about each other's part in the system. The system should be reviewed every year.

Product quality

When a producer wishes to ensure the quality of products, it is necessary to identify where losses in quality are likely to occur and then find methods to control the process and to improve the product. If for example, a problem is due to poor quality raw materials or ingredients, this should be discussed with suppliers and if necessary, the processor should introduce appropriate testing methods with tolerance limits that are agreed with the supplier. If a problem is due to a processing condition, such as the time or temperature of heating, the process control is improved by better staff training, use of thermometers etc.. All changes should be monitored to make sure that they are effective and details of the changes should be recorded in a Production Workbook (Section 2.9.2). Such procedures are intended to control the parts of the process that significantly affect product quality and therefore help the processor to employ staff where they are most effective. Details of quality assurance procedures for each product group are described in the Process Charts in Section 2.2.

Raw materials and ingredients

The main quality factors associated with fruit products are the characteristic flavour and colour of the fruit, the absence of contamination, and in some products, a characteristic texture. However few quality characteristics of fruit products can be measured objectively and fewer still can be measured by machines. Therefore reliance should be placed on subjective assessment by operators and the more operators that examine the raw materials, ingredients, process and product, the greater will be the level of control. The importance of proper staff training and involvement in production are particularly important in fruit processing.

All fruits and vegetables should be processed as soon as possible after harvest to reduce the risk of spoilage before processing. This is particularly important for vegetables to reduce the risk of growth by food poisoning bacteria.

Figure 53. - Decision Tree' for assessing Critical Control Points

(Adapted from How to HACCP, by Dillon, courtesy of MD Associates)

A particular problem facing fruit and vegetable processors in many developing countries is the large number of different varieties of a particular raw material. Not all varieties are suitable for processing and for a processor to be able to make a uniform product, there must be either control over the varieties that are used or a standard system of blending raw materials. Unfortunately this is not always easy to achieve as different varieties of fruits and vegetables are often grown in small quantities by individual farmers.

Orchards or vegetable farms that grow a single variety are unusual and it is a common problem for processors to obtain a sufficient quantity of the required variety, which makes production planning difficult (also Section 2.3.3).

Because most fruits and vegetables mature during a short harvest season, processors must collect and process a large amount of raw materials quickly. In some cases it is possible to part-process and store intermediate products for later production, but there remain specific problems in fruit and vegetable processing that are less evident with other types of processing. For example most fruits and vegetables must be harvested when they are fully mature to give the best flavour and colour in products, but when fully mature many are soft and therefore more susceptible to damage. This damage allows the growth of moulds and yeasts on fruits or rotting bacteria on vegetables. Additionally, damage to a few fruits or vegetables can quickly lead to infection of others and the loss of a whole batch.

Fruits and vegetables should therefore be harvested carefully by cutting them from the tree or plant. With fruits, it is important to leave the stem in place to reduce the risk of infection by moulds and yeasts through an open stem hole.

Bad practices at harvest cause many problems for the processor later on, but the processor often has no control over harvesting methods and the farmers do not understand the processors' requirements. In this situation, it is therefore advantageous for the processor to work with farmers to improve the quality of raw materials. Examples of ways that processors can do this are as follows:

· handlers should be asked to cut their fingernails to prevent them puncturing fruits

· in tropical climates, fruits and vegetables should be cooled after harvest to remove some of the 'field heat' and stored in a cool place or covered with wet sacks

· any damaged pieces should be removed from the bulk as they will lead to rapid spoilage of surrounding foods before processing starts

· fruits and vegetables should not be thrown into piles. They should be filled into crates that are small enough to be carried and not dragged along the ground

· crates should not be over-filled as this crushes the food if boxes are stacked. Ideally, foods should be packed into stackable crates which prevent crushing.

An important aspect of raw material supply is the relationship between growers and the processor and each must have trust and confidence in the other for long term honest dealings.

The agents who normally buy crops from farmers sell to different wholesalers, and some wholesalers buy lower quality for cheaper markets. This means that the transporter is always able to sell a complete load, regardless of the quality. As a result the transporter has no particular interest in safeguarding the quality of the crop. Commercial pressures to carry a maximum load on each journey also mean that the transporter is more likely to pile fruits and vegetables onto a truck, rather than using crates that take up extra space and reduce the value of the load. The agents also carry consumer goods on the return journey to rural areas and are unwilling to return crates to farmers unless they are paid to do so. In the author's experience they are even unwilling to carry collapsible crates which take up less space, for the same reasons. Processors thus have a difficult problem in controlling the quality of raw materials if they do not collect fruit and vegetables themselves from farmers. Contracted farming and management of raw material supply is discussed in more detail in Section 2.6.1.

The first inspection of raw materials may therefore take place as they arrive at the processing unit. The inspection should check that the fruits or vegetables are suitable for processing and reject those that are not. This normally includes a check on the following characteristics (see also Section 2.2 for individual processes):

· maturity (over-ripe or under-ripe)
· colour
· size or shape (for some products)
· visible mould or rots
· serious bruising or cuts
· presence of soil, large amounts of leaves or other materials.

The percentage of rejects should be monitored as this is an important factor in calculating the true cost of useable raw material (see Section 2.3.3)

At this stage in processing, careful inspection by properly trained staff is an important method of maintaining product quality and saving time and money later in the process. It should be remembered that poor quality raw materials produce poor quality final products. It is not possible to improve the quality of raw materials by processing them. Sorting out substandard materials before money is spent processing them is therefore one of the most cost effective methods of ensuring a uniformly high quality in the final product. Similarly, other ingredients should be checked to make sure that they are the correct type and are not contaminated or adulterated.


After initial inspection, fruits and vegetables are washed in potable water, which is chlorinated if necessary (Section 2.5.3). It is important that the process staff are trained to remove any pieces that are rotten as these would quickly contaminate the wash-water and infect good quality raw materials. They should also remove all leaves, insects and other wastes that could contaminate the final product.

The next stages in processing involve preparing fruits and vegetables by peeling, slicing, pulping or filtering. Quality checks during preparation stages are to ensure that all peel is removed, the yield of useable material is calculated (Section 2.3.3) and that slicing produces uniform sized pieces for products such as: banana chips and shreds for marmalade. Any over-sized pieces should be re-sliced. Fruit pulps are filtered using nylon or muslin bags or special juice filters, when a clear product such as squash, jelly or juice is required. Quality control measures during this part of a process are to ensure that bags are properly washed and boiled for at least 10 minutes before each use and that the juice has the required clarity.

Strict hygiene in the processing room and by operators is needed to reduce the risk of both food spoilage and food poisoning. This must include proper cleaning of knives, drying equipment and processing rooms, washing hands, and removal of waste foods as they are produced (Appendix I).

The correct formulation of a batch of ingredients for subsequent processing is critical to both the quality of the final product and the financial viability of the operation. Good control at this stage enables a uniform product to be made in every batch and saves money by not wasting expensive ingredients. Additionally, any mistakes that are made at this stage cannot be easily corrected later and may result in having to throw away a whole batch.

The staff responsible for batch formulation should therefore be given thorough training and a management system that records batch numbers and amounts and types of ingredients used should be put in place (see also Section 2.9.2). When producing dried fruits the amount of residual sulphur dioxide in a product is controlled by law in many countries and sodium metabisulphite for a sulphite dip or of sulphur for burning in the cabinet should each be carefully measured out.

Equipment required for batch formulations includes good quality scales or calibrated cups, spoons or jugs to measure out ingredients and ensure that the same amount is added in every batch. Sugar concentrations in jams, sauces, syrups etc. can be checked using a refractometer (Figure 12). Although this equipment is relatively expensive, it gives an accurate measurement of sugar concentration which is essential for the correct preservation and anticipated shelf life of many products. The reading is recorded as degrees Brix which corresponds to % sugar. The concentration of sugar in syrups can be measured more cheaply using a hydrometer with a scale reading % sucrose. The syrups should be tested at 20°C, which is the reference temperature for the hydrometer.

Figure 54. - Correct formulation of ingredients is an essential feature of quality control

As the sugar content of jams and fruit cheeses increases, so does the temperature of boiling. The sugar concentration can therefore be estimated by measuring the temperature, using a special thermometer that reads up to 150°C. However, the boiling temperature is also affected by the amount of invert sugar in the mixture and staff should have experience of making the product before using temperature alone to control the process. The boiling point also changes with height above sea level and in mountainous regions, producers should first check the boiling point of water and make the necessary corrections. With experience, staff can also estimate the solids content of preserves by cooling a sample of the boiling mixture and noting the texture to see if a firm gel forms.

In some formulations it is necessary to check the pH of a product or the amount of acid that is present, pH is a scale from acidity (pH 1-6), through neutrality (pH 7) to alkalinity (pH 8-14). It can be measured by dipping a piece of pH paper into a sample of liquid food and comparing the colour change with a chart supplied with the paper. For greater accuracy a pH meter should be used.

It should be noted that pH measurement does not tell you the amount of acid present. This is especially important in pickling, where preservation is achieved by the correct combination of acids, salt and sugar. To measure the amount of acid in a product (such as citric acid or acetic acid), a 10g sample of food is mixed with 90 ml of distilled water and 0.3 ml of indicator solution such as phenolphthalein. This is then titrated with 0.1M sodium hydroxide until the pink colour does not change. The amount of acid is calculated using the formula:

% acid = number of ml of sodium hydroxide x one of the conversion factors below:

acetic acid (vinegar) = 0.060, citric acid = 0.064, tartaric acid = 0.075, lactic acid = 0.090. It is necessary to know type of acid in the food before selecting the conversion factor.

The salt concentration in pickling brines can be measured using a special hydrometer (Figure 55). Although other methods, such a salt refractometer and titration exist, they are too expensive or complex for most small scale processors. A sample of brine at 20°C is filled into a large clear glass or plastic cylinder and the hydrometer is placed into the liquid. When it has stopped moving, the scale is read at the surface of the liquid and the reading is converted to % salt using a conversion table supplied with the hydrometer.

Chutneys and pickles rely for preservation on the correct balance of acids, salt and sugar in the final product and they are often not pasteurised. Strict control over hygiene is essential as insects can contaminate the pickle with large numbers of moulds and yeasts during pickling and these can spoil the product during storage. The pickle should therefore be protected from insects and covered at all times to stop dust and other contamination.

Products such as sauces, preserves, drinks and bottled fruits are each heated during processing and the time and temperature of heating is an important quality check. Over-heating causes lowered quality by loss of texture, colour or flavours, whereas under-heating allows enzymes and contaminating micro-organisms to survive and later spoil a product during storage. It is therefore essential that an adequate temperature and time of heating are carefully controlled and operators are trained to ensure that these conditions are maintained for every batch of product. The equipment required for process control includes a clock, a thermometer and for concentrated products such as jams and fruit cheeses, a refractometer to check the final solids concentration.

The shelf life of dried foods depends mostly on the equilibrium relative humidity of the product under the expected storage conditions (Section 2.2.3). This is usually found by measuring the moisture content of the product as described below, but because the relationship between moisture content and humidity varies with different foods, it is necessary to conduct trials to find the highest moisture content at which the food will be stable. This involves taking samples at different times during drying, packaging them and after storage for three to four weeks, checking them for spoilage. The ones that have not gone mouldy are then checked to find the moisture content and this becomes the target level for subsequent production. During drying, the air temperature and drying time should be carefully controlled to ensure that fruits and vegetables are fully dried to the required moisture content.

Figure 55. - A brine hydrometer

The moisture content can be found by carefully drying a known weight of finely chopped food in an oven at 100°C until it does not lose any more weight. The final weight is noted and the '% solids' is calculated using the following formula:

% moisture content is then 100 - (% solids)

The methods described above for process control are each relatively simple and have sufficient accuracy for routine use. They do not need sophisticated or expensive equipment or high levels of skill and they are sufficiently inexpensive to be used routinely by small scale processors. However, many of the methods are comparative and the results can only be compared with other results obtained by the same method. This is acceptable for routine process control, provided that careful attention is paid to ensuring that exactly the same procedure is followed each time.

The time spent on process control should be greater than that spent on testing the final product, because it is better to have control of the process and prevent mistakes from occurring rather than trying to correct a badly made product (prevention is better than cure). This is the basis of the HACCP approach and quality management systems should reward operators for reporting and/or correcting faults in a process as they occur.

Packaging, storage and distribution

Although fruits and vegetables are stabilised by processing, for many their long term preservation depends on the type of package that is used and the temperature and humidity in which packages are stored. For these reasons, it is important that packaging, distribution and storage are included in a processor's quality assurance schedule. Details of the methods of manufacture of packaging materials and potential faults that should be tested for are included in publications in the Bibliography, and a summary of the main quality assurance checks on packaging materials is given below.

The risk of glass splinters in a product which would cause serious harm to consumers, means that bottles and jars are subjected to more rigorous quality checks than other types of packaging. It is essential that all glass containers are checked to ensure that there are no glass splinters or cracks, bubbles in the glass or strings of glass across the interior. Staff who check bottles or jars should be fully trained in the faults to look for and they should only work at inspection for 30-60 minutes at a time to maintain their concentration.

Because of the way in which they are made, the dimensions of glass jars and bottles are also more variable than other types of packaging. It is therefore important to check that a container has the expected capacity, that the neck is properly formed and will allow the lid to fit and that it stands vertically to prevent it breaking in a capping machine. It is also necessary to check the weights of a number of empty jars or bottles to find the heaviest.

This is then used in checkweighing (the checkweight is the weight of the heaviest container plus the net weight of product). If jars or bottles are re-used, they may have contained poisonous materials such as pesticides. They should be thoroughly washed and inspected by smelling them to ensure that there are no residues.

Figure 56. - Checkweighing scales

Filling products into containers is an important control point in a process because in most countries it is an offence to sell an under-weight product and over-filling means that a producer is giving product away. All products should therefore be carefully filled to ensure that the fill-weight is the same as the net weight described on the label (see Sections 2.4.2 and 2.8.3 for details of labelling requirements). A random sample of packages should be checked to ensure the correct net weight using a checkweighing scale (Figure 56). Other information that should be checked at this stage includes whether the label matches the actual product in a pack, that the sell-by date on the pack is correct and that batch code numbers are correct. All data should be recorded in a Production Logbook (Section 2.9.2).

The capacity of a jar or bottle can be checked by weighing a dried container, filling it with distilled water and re-weighing it. The difference in weight is equivalent to the capacity in ml and should be large enough to contain the net weight declared on the label. When a product is filled, there should be a space between the surface of the product and the underside of the lid. This headspace not only allows a partial vacuum to form when hot-filled products cool, but a consistent level of filling is an attractive marketing factor. A simple gauge for checking that product has been filled to the correct level can be made locally (Figure 57). It is placed on the rim of the jar and the level of product can be read where it touches one of the prongs.

Other routine checks for glass containers are the diameter at the neck and body using go/no-go rings (Figure 58) and that containers are round and not oval. Rings are placed around the neck or body to show whether the neck diameter is too large or too small for the lid, whether the neck is circular, to check the outside diameter of the container and whether it is oval or round.

Figure 57. - Headspace gauge

In plastic bags and films, typical faults include 1) incorrect printing, 2) smelling of the odour of solvents used in their manufacture, 3) layers of film on a roll sticking together, 4) poor seal strength, 5) curl, in which a film curls up rather than laying flat and 6) incorrect thickness (known as 'yield'). The last can be measured by cutting 10 squares of film, each 10 cm by 10 cm and carefully weighing them. The result (in grams/square metre) is then checked against the suppliers' specification.

Value is added to raw materials at each stage of processing and by the time it is packaged it has gained most of its final value. Any losses of packaged product are therefore the most serious, resulting in the greatest loss of money to the processor. Great care should therefore be taken in handling and storing packaged foods and they should be stored in boxes on pallets or shelves to keep them off the floor. The storeroom should be cool and dark with a good ventilation to maintain a flow of air and with protection against insects and rodents. Storerooms for ingredients and packaging materials should have similar protection (also Section 2.5.3)

Quality management systems should also be developed to monitor the types and amounts of products, ingredients and packaging materials that are in the storeroom and the time that they remain in storage. Records should be kept by storekeepers to show which materials are transferred into and out of the storeroom and when they were used (see Section 2.9.2). Similarly, the control of product quality does not finish when the product leaves the processing unit and manufacturers should monitor and control the distribution methods to retailers and discuss with them the best ways of storing and displaying the products.

Figure 58. - Go/no-go rings for measuring glass containers

Hygiene and sanitation

Together, a manager and processing staff should apply the HACCP approach to identify all areas of potential hazard in the production of a food and then develop a cleaning plan and personal hygiene rules that ensure safe preparation of the product. The manager should monitor the plan and make sure that all staff are trained and know their own responsibilities. Similarly, it is important that staff are not penalised for having an infection, otherwise they will hide a problem in order to be paid. If staff report a stomach illness or skin infection, they should be transferred to other jobs that do not put them in direct contact with the product. The manager should also provide proper cleaning materials and equipment and allow adequate time for cleaning machinery and processing areas after production has finished.

Cleaning schedules should be drawn up when specific areas of hazard have been identified in a process or in the building. All areas need attention but some carry a greater risk than others. Each worker should know their cleaning responsibilities within a cleaning plan and the manager should take overall responsibility to ensure that cleaning is done to the correct standard and that a cleaning schedule record is maintained. A summary of the quality assurance procedures for a typical fruit and vegetable process is shown in Table 27 and details for individual product groups are given in the Process Charts in Section 2.2.

Table 27. - Summary of quality assurance procedures for fruit processing


Process Activity

Control Point

Raw material harvest

Liaison with farmers, pick fruit and load it into crates or purchase from markets.

Specifications of fruit quality required. Training of pickers and handlers to minimise damage to fruit. Use of correctly designed boxes. Rejection of damaged or rotten fruit and vegetables.

Raw material transport

Transport in crates to processing unit.

Control of fruit temperature by use of water, shade or covers. Correct stacking and handling to minimise damage. Reduce delays and minimise journey time.

Raw material inspection and preparation

Record amount and quality of fruit received. Sort fruit, wash and peel/slice as required for the specific product.

Setting of acceptable standards for incoming fruit. Training in correct sorting, preparation and recording procedures and management to ensure procedures are implemented. Accurate slicing to required sized pieces. Operator hygiene and plant hygiene. Water chlorination. Regular disposal of waste.

Ingredient formulation/batch preparation

Weigh and mix ingredients.

Training in accurate weighing and keeping records of ingredients used.


Part-processing if fruits are to be stored for later use. Heating, drying, pickling etc. to make the required product.

Preparation of processing schedules and training of operators to ensure: - control of temperature and time of heating or drying, - correct amounts of ingredients added at the correct time in the process. Establish standards for operator hygiene and schedules for cleaning of equipment and processing room.


Fill product into packages, seal and label. Pack into distribution boxes.

Establish specifications for package quality (especially glass containers), labels and fill-weights. Implement inspection, check-weighing and recording procedures

(From: Quality Assurance for Small-Scale Rural Food Industries, courtesy of FAO)

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