The overall quality of a product is judged by a number of parameters, Perishable products can be defined by their stable quality features and by those that change. For instance, for fruit the parameters are size, ripeness and fullness. For salmon fillets, visible features such as the pinkness of the flesh, the absence of blood spots, the texture and the absence of gapping in the flesh are important, Other parameters can be considered; for example, the surface dryness of soft fruits can influence the probability of mould growth.

Defining information such as the weight of the unit and the number, size and grade of the items is stamped on the outer packing, and these features do not change. If the date of production is included on the packaging it implies that the goods are perishable and that some of the quality features change with time.

Good quality is judged by freshness, expected appearance, smell and texture. Since these features change with time, the maintenance of good quality depends on retarding this natural progression as much as possible. The range of changes varies among products: in fats unacceptable flavour changes occur because of oxidation; in fruits ripening causes changes in colour, texture and sweetness; in head-on, shell-on prawns blackening can occur; in meat the slow activity of enzymes causes texture changes; in produce held at temperatures above -10°C microorganisms can begin to grow and cause change and quality loss; in grains and other dry products absorbed moisture can allow mould to grow. Microorganisms affect many products and may cause soft rots. Fresh vegetables naturally dehydrate (wilt), and the loss of crispness is a loss of quality,

Stages in a complex journey - Diverses étapes d’un trajet complexe - Etapas de un viaje de ida y vuelta

Quality loss

Quality loss is judged in terms of demonstrable and inferred defects. Some faults are indisputable even to the untutored eye, By sorting, the proportion of food damaged can be assessed and the defective product may still be acceptable to a section of the market. Quality loss is also judged by interpretation of signs that indicate that the product was handled less than optimally, If the temperature recorder of the container of cargo shows deviations from the requested temperature it is inferred that the product is damaged, and the cargo is examined for visible defects.

Physical changes may indicate how the product was handled en route. For example, frozen products may show ice formation which indicates that temperature fluctuations in refrigerated storage have occurred, causing water to sublime from the product and then to recondense inside the packet, This leads to dehydration of the product, known as freezer burn, Severe temperature abuse may be evident through signs of thawing and refreezing, seen when, for example, individually quick-frozen items stick together.

To avoid poor practices and give guidance for improvement, FAO and the World Health Organization (WHO) have developed a series of guidelines and codes of practice both to protect the quality of products and to ensure that temperature control can be maintained and appropriately monitored (Codex Alimentarius Commission, 1993,1994), The Codex Alimentarius Commission and the European Economic Community (EEC) (now the European Community (EC)) have published examples of the controls required and recommended sampling methods (Codex Alimentarius Commission, 1994; Commission of the European Communities, 1992a, 1992b).

When does quality loss arise?

Any perishable product has a finite life span under given conditions which is divisible into two stages (Figure 3), During the period of apparent quality stability, from X to A, the quality is in fact reduced to a point (A) where there are noticeable changes in one or more of the quality parameters. During the second stage, from A to B, the changes continue, eventually rendering the product unacceptable at B.

Real and apparent quality loss with time - Perte de qualité réelle et apparente au fil du temps - Pérdida de calidad real y aparente con el tiempo

Problems may arise under three circumstances:

• when the product is transported very near the end of period X-A;

• when the rate of quality loss is accelerated, that is the slope of X-A (which is primarily temperature dependent) is steepened and the product moves more rapidly from period X-A into period A-B;

• when a product is already in period A-B when the journey begins.

While quality loss occurs naturally, the time it takes for a perishable product to become unacceptable depends on handling, storage and temperature experience, Ideally a product should arrive and be distributed completely within period X-A, Even under optimal conditions, time is not on the side of perishable products, and they are more likely to arrive in an acceptable condition if only a short time within this period has elapsed prior to dispatch.

Need for quality definitions

In a contract between a seller and a buyer each has to know the quantity, price, availability and quality of the product that is changing hands, Does the supplier guarantee shipment of goods that leave the factory at a certain quality? Does the buyer expect that those goods will be identical in terms of quality on arrival? Does the buyer inform the seller of the acceptance criteria and build in some tolerance for quality loss with time? Does the carrier, working between the buyer and the seller, have an interest in knowing what the quality is?

In some countries the export quality of certain goods is controlled, particularly if the country wishes to emphasize an image of quality in selling, For some goods an accompanying health certificate or phytosanitary certificate may be required to control the transmission of disease to human beings, animals or crops. Some countries have instituted systems of quality management in particular sectors of the food industry (Garrett and Hudak-Roos, 1992; White and Noseworthy, 1992; Lima dos Santos, 1992), generally drawing on internationally recognized standards of good management practice such as ISO 9002 (International Organization for Standardization, 1994), Such cross-industry systems are intended to raise and ensure the quality of the products.

Suppliers can often use quality control and quality assurance methods, such as those developed for seafoods by FAO (1994), to ensure that goods meet a definable standard, The factory should be able to certify the quality of each consignment; however, the terms may be limited, covering only certain parameters and omitting those that are perceived as crucial at the time of receipt.

Certainly the standards for all principal foods described in the Codex Alimentarius provide a fundamental basis for mutually understood product descriptions. The standards define limits for composition and contaminants and in some cases list the tolerances for defects (Codex Alimentarius Commission, 1990).

When the sellers and buyers are known and the goods travel familiar routes, the opaqueness of quality definition on paper may seem unimportant. However, with goods travelling greater distances and being bought by large, powerful, possibly multinational interests, the nature of trade is changing, The personal element may be diminishing, and the formal description of goods is becoming more essential. Many goods are sold through markets, and at the time of production the buyer may be unknown.

Where the goods to be purchased are of the highest quality and command the highest price, the seller and the buyer may work together (Spriegel, 1993). In fact, good manufacturing practice (GMP) would demand the development of a manual for use between them which would provide details of many features and which might use photographic data to define some parameters. However, if a declared definition of the product’s quality is lacking, situations arise when the receiver’s perception of tolerable quality loss differs from that of the sender.

Between the seller and the buyer is the carrier. Worldwide, the costs and availability of transportation as well as levels of assurance of quality maintenance vary (Gill and Phillips, 1993), Some but not all transporters develop considerable expertise in the carriage of products. If product quality loss occurs in consignments, determination of when loss has occurred is crucial in dispute settlement. Thus, expertise and good management practices at all stages are vital.