Get our free book (in Spanish or English) on rainwater now - To Catch the Rain.
Quality Control (Practical Action Technical Brief)
Quality control (QC) is not an optional extra in food processing; neither is it something done only by large manufacturers. It is an essential component of any food processing business. The purposes of quality control are:
• To protect the customers from dangers (eg contaminated foods) and ensure that they get the weight and quality of food that they pay for.
• To protect the business from cheating by suppliers, damage to equipment (eg stones in raw materials) and false accusations by middlemen, customers or suppliers.
• To be sure that food laws operating in a country are complied with.
Quality control need not be time consuming or expensive, and the results of quality control tests should help save money in the long run. In general, quality control procedures should be as simple as possible and only give the required amount of information. Too little information means the test has not done its job; too much information and management decisions may be delayed or confused.
Quality control is used to predict and control the quality of processed foods. It is no use producing a food, testing it to find the quality, and then trying to find a buyer for that particular batch of food. Quality control is used to predict the quality of the processed food and then control the process so that the expected quality is achieved for every batch. This means that quality specifications must be written and agreed with suppliers or sellers, and control points must be identified in the process.
The quality of foods or ingredients can be measured in different ways but one popular method is to describe 'quality attributes', as in Table 1. A specification can then be written and agreed with the supplier or seller, which lists the quality attributes that are required in a food. An example of a quality specification for tomatoes to be used for processing into paste is shown in Table 1.
|Colour||Orange/red||More than 10% green|
|Damage splitting insect mould||Less than 5% Less than 5% None||More than 5% More than 5% Any evidence of mould|
|Hardness||Soft to over-soft||More than 10% hard|
Table 1: Quality attributes for tomatoes used for tomato paste.
A number of points arise from such a specification:
• A representative sample of the food must be tested to make sure the whole batch meets the specification. (For small batches it might be possible to examine every item.) The size of sample needed for testing can be calculated, but this is fairly complex, and usually unnecessary for a small- scale business.
• The percentage of substandard items which cause a batch to fail the test can be increased or decreased depending on how reliable the supplier is, or how important the particular attribute is to the seller/manufacturer.
• Some attributes may need to be tested with equipment in order to avoid arguments over interpretation. In Figure 1, for example, the hardness could be tested with a simple 'penetrometer' to define what is 'hard' and what is 'soft'.
Quality attribute Example
The size and shape of the tomatoes is not important because they are to be crushed to a pulp. In other examples (such as fruit for bottling) the size might be important. The ripeness and flavour of the tomatoes - assessed by colour and hardness -, and damage caused by poor storage and handling, are very important: the specification concentrates on these. Each specification takes account of the intended use of the products and the most likely important faults that could be expected.
|Quantitative||Required sugar content of fruit (eg 15%)|
|Harmful substances||Aflatoxin in groundnuts|
|Microbiological||Number of bacteria in a food|
|Nutritive value||Vitamin content of a food|
|Additives||Artificial flavours, thickeners etc|
|Colour||Ripeness of fruit|
|Size, shape (appearance)||Size of chopped food, particle size of flour|
|Thickness or texture||Juice consistency, toughness of meat|
|Taste||Saltiness, sweetness, sourness and bitterness|
|Flavour||Characteristic flavour of tomato|
In every food process there are particular stages which affect the quality of the final product. For example, the amount of heating given to pasteurise juices affects their colour, flavour and storage life; in sausage making, the amount and type of grinding affects the texture of the meat. Such stages are identified as control points, and quality control checks are made at these points in order to control the process.
Manufacturers therefore need first to identify the control points in their process - using outside technical assistance if necessary - and then to set up a specification for operators to use. For example, in jam making, the amount of pectin, fruit and sugar should be carefully controlled: therefore, the weighing of ingredients is a control point, as the weights of each ingredient must be specified and carefully weighed out.
In the same way, other control points would be: the acidity of the jam, the sugar content after boiling and the temperature of filling. The mix should be checked for correct acidity, the sugar content checked during boiling (using a thermometer or refract meter), and the temperature checked before filling (using a thermometer).
Checks at control points can therefore be used to control the process and to ensure that each batch of product is of similar quality.
References and further reading
• Food Processing Equipment Design Technical Brief Practical Action
• Food Processing Building Design Technical Brief Practical Action
• Food Poisoning & Its Prevention Technical Brief Practical Action
• Quality Assurance for Small-scale Rural Food Industries: FAO Agricultural Series Bulletin 117, P. Fellows, B. Axtell, M. Dillon. Midway Technology Ltd, Northampton, United Kingdom Food and Agriculture Organization of the United Nations, Rome, 1995 http://www.fao.org/docrep/V5380E/V5380E00.htm
• Quality Assurance/Control in Food Processing. Contained in: Food Fortification - Technology and Quality Control. (FAO Food and Nutrition Paper - 60) http://www.fao.org/docrep/w2840e/w2840e00.htm#Contents
• Fruit and vegetable processing: Chapter 10 - Quality control/quality assurance and international trade; good manufacturing practices (gmp); hygiene requirements; hazard analysis and critical control points (haccp) http://www.fao.org/docrep/v5030e/V5030E0t.htm
• Quality and process control in the food industry Pearl Adu-Amankwa. Food Research Institute, P.O. Box M.20, Accra. Published in The Ghana Engineer, May 1999 http://home.att.net/~africantech/GhIE/QPCFood.htm
• Agreement on the Application of Sanitary and Phytosanitary Measures (SPS) and Agreement on Technical Barriers to Trade (TBT). Module 7 - National Food Control Systems: Components and Operation. Food Quality and Standards Service. Food and Nutrition Division, FAO. http://www.fao.org/docrep/003/x7354e/x7354e07.htm
• Food Hygiene Training: A Guide to its Responsible Management Institute of Food Science and Technology 1992
• Making Safe Food: A guide to Safe Food Handling and Packaging for Small-scale Producers ITDG Publishing 1998
• Starting a Small Food Processing Enterprise ITDG Publishing 1996
Useful organisations and contacts Food and Agriculture Organization of the United Nations, Rome, Italy Website: http://www.fao.org/
Viale delle Terme di Caracalla 00153 Rome, Italy Tel: +39-06-57051 Fax: +39-06-57053152 Email: FAO-HQ@fao.org Media Relations Tel: +39-06-57053625 Fax: +39-06-57053699
This document was produced by Barrie Axtell (2003) and updated by Tony Swetman (2008) for Practical Action.
Practical Action The Schumacher Centre for Technology and Development Bourton-on-Dunsmore Rugby, Warwickshire, CV23 9QZ United Kingdom
Tel: +44 (0)1926 634400 Fax: +44 (0)1926 634401
E-mail: email@example.com Website: http://www.practicalaction.org/