2.4 Herb and spice products
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The process flow chart for selected herb and spice products is shown in Fig. 32 (see Figure 32: Process flow diagram for herb and spice processing) and a summary of the main quality assurance procedures for herb and spice processing is shown in Table 9 below. The quality assurance procedures in the table are discussed in more detail in the following chapter.
Table 9: Main quality assurance factors for herb and spice processing
|Non permitted pesticides/ herbicides||Very high, sale may be impossible. Liaison with growers.|
|High levels of permitted pesticides/herbicides.||Very high. Liaison with growers.|
|Infestation||High, fumigation may be required.|
|Foreign matter||Medium. Can be removed. Sorting.|
|Poor microbiological quality.||Medium. Improve harvesting, handling and washing.|
|Mould growth after packaging.||High. Dry to correct moisture content. Improve packaging materials.|
Most dried foods are comparatively low risk products in terms of causing food poisoning as they rely upon drying to a sufficiently low moisture content to prevent the multiplication of micro-organisms. However, herbs and in particular spices, are an exception and commonly contain very high levels of micro-organisms including those that cause food poisoning. In addition, they are commonly subject to contamination with foreign matter.
There are two main reasons for these high contamination levels. First considerable contamination occurs during harvesting, washing and sun drying which takes place 'on farm', often under primitive conditions. Secondly, subsequent processing of herbs and spices is restricted to low temperature drying, grading, cleaning and grinding. They are not heat treated because this would result in loss of flavour and micro-organisms may thus survive processing. Fortunately for the producer, public health risks to the consumer are greatly reduced as herbs and spices are used as minor flavouring ingredients and well cooked in the home.
The quality assurance and control procedures that need to be considered when processing herbs and spices fall into three main areas:
The manufacturer needs to consider each of these aspects in detail and develop a HACCP plan to identify problem areas, potential hazards and to put checks into place at critical points to meet the central objective: that is to supply high quality products to the consumer.
From cultivation to raw material purchase
In most developing countries herbs and spices tend to be grown by smallholders. Their high value means that a good financial return may be obtained for people possessing a small plot of land. This has several immediate implications for the purchaser including:
Quality assurance in raw material supply
Processors thus face a complex range of problems even before the product enters the processing unit and at first sight these appear to be beyond their control. However, as has been stated in other chapters of this book, 'a good product cannot be made from second rate raw materials'. For this reason the greatest gains in finished product quality may be made by carrying out a HACCP analysis that focuses on these pre-purchase areas.
The first step is to understand the supply chain from grower to purchaser and then identify all potential hazards and their severity.
The next step is to consider what can be done to eliminate or minimise these risks. In this context, the most important aspect is the relationship between the growers and the buyer. Each must have confidence in the other. The processor should consider ways in which the grower may be assisted and this will also give greater confidence over the raw material quality. Ways of helping are many and varied but the following examples may guide the reader to develop the correct tactics and systems.
Many smallholders are forced to sell through agents as they are also a source of credit during periods of hardship or when material inputs are required. The entrepreneur may assist in a similar way by offering contracts with phased payments against an agreed quality standard. This may be particularly useful for buying inputs such as herbicides and pesticides. The entrepreneur may purchase these in larger quantities at lower prices and distribute them to growers in the correct amount, depending on the area of the crop to be treated. In this way the buyer has considerable control over both the type and level of chemicals used. In other cases the distribution of selected seed may provide the farmer with higher yields and give the buyer more uniform raw materials.
Investigation and training are also good ways to improve quality. A buyer is often well placed to organise and fund such activities, as the following account from Guatemala in Central America shows: here smallholder members of a co-operative were attempting to supply herbs, which after drying were to be sold to a major multi-national food company which applies very high quality standards. Despite rigorous washing and sanitising, it proved impossible to meet the company's microbiological standards.
A local institution carried out some tests which showed heavy contamination not only on the outer surface of the plants but also internally. It was clear that simple washing would never solve the problem, but the final solution proved to be very simple. First the use of raw manure as a fertilizer was stopped as this was the major source of contamination. Secondly harvesting methods were changed and the cut herbs were placed in clean baskets off the soil instead of being laid on the ground. It had been shown that when a plant is cut, its stem attempts to seal itself by sucking up moisture, which in this case contained microorganisms from the soil. The farmers were trained in the proper management of manure and hygienic harvesting. The problem disappeared and a contract was won.
Farmers may also be trained to construct and use solar dryers that can provide substantially more hygienic drying conditions. A typical low cost dryer constructed from readily available materials is shown in Fig. 33 (see Figure 33: Brace type solar dryer costing about US$ 20 and capable of drying 10 kg of produce per batch). Such training should however stress that the role of the dryer is not to dry more quickly, but to give a better quality product.
Dried spices that are stored on the farm often become rapidly infested with beetles and moths. Growers usually put dried products in dirty gunny sacks which are laid on the floor in a corner of the house. Training in correct storage methods may dramatically reduce infestation levels and buyers may also directly assist the growers by providing heavy-gauge plastic bags or large tins with lids for on-farm storage.
The technique of "sunning" is used to prevent infestation of grains by heating them in the sun and this is also applicable to spices (see publications in Appendix 1).
In many cases growers wash herbs and spices using heavily contaminated water. Training farmers to add a little household bleach to the water will reduce levels of contamination (see Chapter 1.3 and Chapter 3: chlorine measurement).
It may also be better for buyers to avoid purchasing from traders. Larger businesses may find it worthwhile to have a trained employee who is responsible for visiting farmers and purchasing their crops. It is easy to check the quality of a small amount of reasonably uniform material from one grower. However, it is exceedingly difficult to assess the quality of several tons of mixed crops that may have originated from perhaps 100 growers.
To summarise, it is possible for an entrepreneur to improve the quality of incoming herbs and spices by finding ways to have more control over their production, including for example:
Quality assurance and control in the processing plant
It has been repeatedly stressed in this book that high quality finished products can never be made from poor quality raw materials. Although all stages in a process are important, errors in early stages build up, becoming larger problems later, which cannot usually be corrected. Careful attention to the initial stages of a process is therefore very beneficial in maintaining quality.
The first step in the process is to check each batch of incoming raw material and record the results against the name of the supplier in an Incoming Materials Test Book (Fig. 25). Most dry spices and herbs are delivered in gunny sacks and a 'thief sampler' (Figure 34: A thief sampler being used to take representative samples) is useful to remove samples from the centre of the sack for testing.
The most common checks that a small or medium scale producer can carry out on fresh material include the following:
Appearance and presence of contaminants
A sample of the incoming raw material should be spread on a sheet of clean paper and carefully examined for signs of infestation, moulds, foreign matter, rodent hairs, broken seeds etc. In some cases, placing a small sample in water may reveal spices which have been internally attacked by insects as they will tend to float. In other materials the size of pieces may be important and a simple test procedure can be developed to check the range of sizes, by either sieving or weighing a known number of seeds (Chapter 3: sieving tests). A 'filth test' (Chapter 3) can be used to identify insect parts.
Odour and flavour
Small and medium scale producers are not able to chemically analyse the flavour-bearing essential oils in the product. With experience however, abnormalities may be detected by tasting.
In the case of a unit processing dried herbs and spices, a similar examination system to that used for fresh crops is required, together with a determination of moisture content.
The moisture content of dried herbs and spices is very important and if it is too high moulds and yeasts will be able to grow. The grower is always anxious to sell the maximum amount of water! The moisture content may be checked using scales and an oven (see Chapter 3: moisture content measurement, spices).
Control of processing
The processing of herbs and spices usually involves most of the following stages:
The factory may thus require two areas: a wet area and a dry area (Figure 35: Plant layout showing wet and dry areas). The general recommendations on hygienic management of food processing buildings and equipment described in Chapter 1.2 apply to this process.
Washing most commonly takes place when fresh herbs are delivered to the processing unit. Spices are rarely washed, but notable exceptions are nutmegs which are dipped in water to remove unsound nuts or "floaters", and cardamom which may receive a sodium bicarbonate dip to preserve its green colour.
In the case of herbs it is most important to wash them as soon as they arrive in order to remove 'field heat' and thus slow down the growth of micro-organisms. Large amounts of clean chlorinated water are required, using chlorine levels that are higher than those found in tap water. Chlorine levels should be monitored to avoid flavour taints in the finished product and simple test kits are available (Chapter 3: chlorine measurement).
If available, special disinfecting/cleaning agents are superior to chlorinated water. These usually contain chemicals known as quaternary ammonium compounds that have a stronger, longer lasting action than chlorine. They are usually supplied pre-mixed with wetting detergents that produce better washing.
Washing may be achieved at a small scale in large shallow tanks that allow operators to move the produce freely through the water. If concrete tanks are used they should ideally be tiled. Soil and other foreign matter is washed off the raw materials and frequent changes of water are therefore needed. A better method is to continuously circulate water through a filter. Ideally several tanks should be used, the first for removal of heavy soiling and subsequent cleaner tanks for final washing.
At a larger scale continuous washers are more appropriate. Here a moving conveyor picks up the produce and carries it under powerful sprays of water. Recirculation through a filter is normal to reduce water consumption.
Although spices are rarely washed in most processing units, rapid washing and redrying offers the greatest potential to improve quality. Most contamination by micro-organisms and soils on spices such as black pepper, cardamoms and pimento is surface contamination. Washing or spraying for a minute or so with chlorinated water removes most soils and reduces microbial levels. Quick washing only wets the surface and a short re-drying period is all that is required to reduce the moisture to the required level.
Other cleaning methods
Winnowing is carried out to remove stones, chaff, dust, broken seeds, etc. from dry spices. This may be carried out very simply using a winnowing basket and allowing the wind to blow away light material such as dust or chaff. Stones are removed by hand. Such simple methods are only suitable for very small quantities of raw material. Cleaning of leafy herbs has to be done manually and any unsound material or foreign matter removed.
Small enterprises generally use electric powered winnowers which have a variable speed fan and adjustable baffles that separate stones from sound material and light material (chaff, dust). It is recommended that the weight and type of contaminants from each supplier are recorded in the Raw Material Inspection Book so that low quality suppliers may be identified.
Various types of dryers are used for processing herbs and spices, ranging from simple sundrying to gas or kerosene-fired dryers. A common example is shown in Fig. 36 (see Figure 36: Batch tray dryer).
A detailed explanation of such dryers is not possible in this book but useful publications are listed in Appendix 1.
The type of dryer that is used and the way in which it is operated may have a significant influence on the quality of the finished product in the following ways:
Herbs and spices must be dried to a moisture content that is low enough to prevent the growth of micro-organisms such as moulds and bacteria.
After drying, the material should be packed quickly into clean heavy-gauge plastic sacks to avoid any moisture pick-up. Workers should not directly handle the food, but use scoops or clean gloves. Sacks should be labelled and dated and samples should be taken for moisture testing. It is a good idea to retain samples in airtight bottles for future reference.
Dried products must also be stored under proper conditions, off the floor on wooden pallets and away from walls so that the store-room may be kept clean. Herbs may lose their bright colour if exposed to sunlight and over-wrapping with black plastic sheets is recommended. The store should be regularly inspected and cleaned and stock should be used in rotation.
In some cases spices may be sold ground or blended to form a mix such as curry powder. Grinding is normally done using either a hammer mill or a disc mill. Ground spice should be passed through a fine sieve to give a product with a uniform particle size. Finely ground spices absorb water much more quickly than whole spices and it is important that the ground material is quickly packed into airtight containers.
Grinding may give rise to a considerable amount of fine dust which attracts insects. Ideally the mill should be housed in a separate room that can be thoroughly cleaned at the end of the day. A small vacuum cleaner is recommended for cleaning up fine dust as brushing tends to push dust into the air for it to settle elsewhere. Fine spice dust may be an irritant to workers and protective masks and goggles should be provided.
Packaging and storage of finished products
The type of packaging needed for herbs and spices depends on the product, the intended market and the types of climate that the food will be exposed to. A herb or spice that is marketed in a cool dry area may only need simple packaging such as paper. The same product sold in a hot, humid area needs considerable protection against moisture pick-up. Producers may therefore need to decide on different packs for different markets. Selection of packaging requires much thought and attention as it represents the final defence for the product in the chain to the customer. Some useful publications on packaging are listed in Appendix 1.
Most herbs and spices are packed in plastic film as either large bulk bags or small retail packs. The processor may carry out a number of simple checks on films (see Chapter 3: packaging film measurement).
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