Preservation of Fruits and Vegetables GIRDHARI LAL, G.S. SIDDAPPA and
G.L. TANDON Central Food Technological Research Institute, Mysore
Rewritten by
GS. SIDDAPPA Formerly Chairman, International Food Technology Training Centre Ex-Senior Scientific Officer, Division of Fruit Technology Central Food Technological Research Institute, Mysore
HIW3Mtr ICAR
Published by
Directorate of Knowledge Management in Agriculture Indian Council of Agricultural Research New Delhi
First Published Second Edition (Revised and expanded) First Reprint of Second Edition Second Reprint of Second Edition Third Reprint of Second Edition Fourth Reprint of Second Edition Fifth Reprint of Second Edition Sixth Reprint of Second Edition
January 1960 August 1986 June 1998 February 2009 May 2010 February 2011 January 2013
October 2013
Project Director (DKMA) : Dr Rameshwar Singh
Incharge (English Editorial Unit) : Dr Arana T Kumar
Chief Production Officer : Dr V K Bharti Officer ( Production) : Kul Bhushan Gupta
Technical
All rights reserved Š 2013, Indian Council of Agricultural Research, New Delhi
ISBN : 978-81-7164-090-4
Price : ? 300
Published by Dr Rameshwar Singh, Project Director, Directorate of Knowledge Management in Agriculture, Indian Council of Agricultural Research, Krishi Anusandhan Bhavan-I, Pusa, New Delhi 110 012 and printed at M/s Chandu Press, D-97, Shakarpur, Delhi 110 092.
CONTENTS FOREWORD PREFACE ACKNOWLEDGEMENT 1.
PRINCIPLES OF PRESERVATION Canning and bottling fruits and vegetables. Principles of Food Processing
2.
COMMERCIAL CANNING Investment. Factory Site. Factory Building. Water Supply and Drainage. Machinery and Equipment. Canning Process. Sorting and Grading. Washing. Peeling. Coring and Pitting. Lye Peeling. Blanching. Can Filling. Processing Heat Penetration in Cans. Processing Methods. Effect of Altitude ©n Processing Time. Effect of Altitude on Processing Pres¬ sure and Temperature. Effect of Acidity on Sterilization. Effect of Processing on Strain in Can. Cooling. Testing for Defects. Labelling, Sorting and Packing
3.
CONTAINERS FOR PACKING Tin and Glass Containers. Tin Containers. Tin Plates, Lacquering. Manufacture of Cans. Testing of Cans. Mech¬ anical Defects. Size of Cans
4. SYRUPS AND BRINES FOR CANNING Sugar Syrups. Preparation. Testing Syrup Strength. Tem¬ perature Corrections. Syrup Calculations
5.
CANNING FRUITS Apple. Apricot. Banana. Black berries. Cherries. Fig. Grape fruit. Greengage. Guava, Jack-fruit. Litchi. Loquat. Mango. Orange. Papaya. Peach. Pear. Pineapple.Tlum. Berry fruits. Miscellaneous Minor Fruits. Processing Minor and Lesser Known Fruits
6. CANNING VEGETABLES Asparagus. Beans. Beetroot. Cabbage. Carrot. Cauliflower. Gram. Mushroom. Okra (Lady’s- finger). Peas. Potato. Tomato. Turnip. Other vegetables. Parwal. Spinach. Karela. Tinda. Ivy-gourd. Curried Vegetables
xii 7.
CONTENTS
SPOILAGE IN CANNED FOODS Discolouration of Fruit Products. Metallic Contamination.
83
Colouring Matter in Fruits and Vegetables. Discolouration
in Canned Food Products. Corrosion and Perforation of Tin Plate. Spoilage by Micro-organisms. Spoilage by fungi. Storage Life of Canned Products. Hydrogen Swells and Perforations
8.
FRUIT JUICES. SQUASHES AND CORDIALS Equipment for Fruit Juices. Double Operation. Presses. Pulping Equipment. Deaerater and Flash Pasteuriser. Fruit Beverages. Preparation and Preservation. Straining. Filteration and Clarification. Preservation of Fruit Juices. Preservation by Addition of Sugar. Preservation by Freez¬ ing. Preservation by Drying. Preservation by Carbonation. Preservation by Filtration. Other Methods of Preservation
93
9.
FRUIT BEVERAGES Squashes and Cardials. Juices. Syrups. Carbonated Bevera¬ ges. Fruit Juice Concentrates. Fruit Juice Powders
124
10.
FERMENTED BEVERAGES Grape Wine. Fermentation. Champagne. Port. Muskat.
152
Tokay. Sherry. Cider. Perry. Orange Wine. Berry Wines
11.
JAMS, JELLIES AND MARMALADES
156
Jams. Fresh Fruits. Frozen Fruits. Fruits Preserved by Heat Treatment. Sulphitation for Storing. Storage. Jellies. Fruit for Jelly. Extraction of Pectin. Theory of Jelly Formation. Strength of Pectin Jellies. Packing. Some Typical Jams and Jellies. Marmalades. Jam marmalade 12.
PRESERVES, CANDIED AND CRYSTALLISED
19S
FRUITS Preliminary Processing. Candied, Glaced and Crystallized Fruits. Crystallized Fruit. Improved Equipment for Manu¬ facture of Preserves. Some Common Preserves. Other Preserves and Candied Fruits
13.
TOMATO PRODUCTS Toma.o Juice Tomato Puree. Tomato paste. Tomato Cocktail. Tomato Ketchup. Chilli Sauce. Tomato Sauce Tomato Soup. Microbiology
214
CONTENTS
14. CHUTNEYS, SAUCES AND PICKLES
xtii
235
Chutneys. Thin Sauces. Thick Sauces. Soups and Other Mixes. Pickles. Pickling Process. Keeping Quality. Causes of Spoilage. Various Pickles. Oil Pickles. Other Pickles
15.
VINEGAR
270
Types. Method of Preparation. Raw Material, Processing and Fermentation. Preparation of Vinegar. Post-ProducÂŹ tion Processes. Checking Spoilage. General
16.
DRYING OF FRUITS AND VEGETABLES Sun-drying. Mechanical Dehydration. Process Variations. Processes for Vegetables. Other Methods of Dehydration. Packing and Storage
283
17. BY-PRODUCTS Utilizing Waste Material. Citrus By-products. Citrus Oils
308
18.
MANUFACTURE OF PECTIN Pectin from Apples. Pectin from Citrus Fruits. From Other Materials. Pectin Preparation. Uses of Pectin
320
19.
WATER FOR CANNERY Qualities of Water. Purification of Water. Analysis of Water. Major Mineral Constituents. Bacteriological Examination. Results of Analysis of Water. Chlorination
329
of Water
20
FOOD COLOURS Certified Colours. Banned Colours.
349
21.
VITAMINS
361
Processing
22.
PROCESSING AND PRESERVATION FOR A SMALL SCALE INDUSTRY Products for Small Scale Manufacture. Equipment. Medium and Large Sized Multi-Commodity Processing
365
23.
REFRIGERATED STORAGE
368
xiv
CONTENTS
24.
PROCESS TIME FOR CANNED VEGETABLES AND NON-ACID FOODS Graphical Method. General Method. Equal-Time Interval Procedure. General Considerations. Determining ‘F’ value from Death-rate Data
APPENDICES I Reference Tables II Fruit Products Order 1955 (As amended up to 19-1-1963) III Specifications and Packaging of Some Special Products
373
386 403 448
Orange Juice Concentrate
IV
Some amendments to the P. F. A. Act and Rules
451
V
Limits for Use of Preservatives
453
Conversion Data Imperial to Metric conversions
455
BIBLIOGRAPHY
458
INDEX
482
VI
CHAPTER 1
PRINCIPLES OF PRESERVATION EVER since man gave up his arboreal habits and settled down to a pastoral life, his efforts have been directed towards gathering and storing foods, when they are in plenty, to meet his needs during the days of scarcity. This became more and more imperative as he made rapid strides towards a higher social status and civilization. In the case of foodgrains, nature helped him in reducing their moisture content to a level when they could be stored carefully without much deterioration. In the cold regions, the low temperatures prevailing there helped to prolong the keeping quality of perishable foods such as meat and fish. In the hot regions, the sun helped to dry put perishable foods like fruits, vegetables, meat, fish, etc., so that the dried material could be kept longer. In some cases, salting as in the case of fish and some of the vegetables, and natural fermentation as in the case of wines, ciders, vinegar, etc., extended to man the availability of a few of his important foods. In the majority of cases, heat or cold was the principal agent employed to preserve many of his foods. Even today the same principle is employed for preservation of perishable foods, although the technical advances in its application have been most amazing. The ‘biltong’ of South Africa, which is a form of sun dried meat is a typical early example of its class of preserved foods. Dried fruits and fermented beverages have been known to man from time immemorial. Pickles of vegetables and fruits, and of fish, also have been popular for hundreds of years. Many of these techniques of preservation of foods have, however, in recent times, been placed on a scientific basis, with the" result that today food preservation industry is perhaps the largest industry in the world. The modern methods of food preservation in general and of fruit and vegetable preservation in particular may be broadly classified as follows : L Physical Methods (a) By removal of heat (preservation by cold)
(b) By addition of heat (thermal processing)
i. ii. iii. iv. i. ii.
Refrigeration Freezing preservation Dehydro freezing preservation
Carbonation Stationary pasteurization Agitating pasteurization/sterilizaÂŹ
tion
2
PRESERVATION OF FRUITS AND VEGETABLES
(c) By removal of water (evaporation or dehydration)
(d) By irradiation
iii. Flash pasteurization/HTST processing etc. i. Sun-drying ii. Dehydration iii. Low temperature evaporation or concentration iv. Freeze-drying v. Accelerated freeze-drying vi. Foam-mat drying vii. Puff drying, etc. Dosing with U.V. or ionizing radiation etc.
II. Chemical Methods (a) By addition of acid such as vinegar or .lactic acid (b) By salting or brining
Pickled vegetables, fish, and meat Vegetable/fruit pickles, salted fish, etc.
salt-cured meat and pork etc.
(c) By addition of sugar and heating (d) By addition of chemical preservatives
Fruit preserves, jams, jellies, marmalades, etc. i. Using water soluble salts of sulphur dioxide, benzoic acid, sorbic acid and a few like hydrogen peroxide, etc. which are permitted as harmless in foods. ii. .By means of substances of bacterial origin such as tylosin, resin, etc. which are permitted to a limited ex¬ tent, in some cases as harm¬ less additives.
III. By Fermentation Alcoholic and acetous fer¬ mentation as in the case of fruit wines, apple cider, fruit, vinegar, etc.
PRINCIPLES OF PRESERVATION
fV. By Other Methods
3
A judicious combination of one or more of the methods mentioned above for synergisÂŹ tic preservation. Although all the main classes of preservation have been employed in varying extents in the case of a variety of fruits and vegetables, some of them are of particular significance now in view of their economic imÂŹ portance. They are efficient, comparatively simple in operation, have universal application and as such have attained commercial importance. [ Some of the more important applications of the different methods are mentioned briefly in the following section. More detailed applications of such methods will be described in the subsequent chapters. Preservation by addition of heat in various ways is perhaps the earliest and the most common method of preservationĂż It is generally known as preservation by canning or heat processing in hermetically sealed containers made of tin plate or glass, or more recently of heat-resistant plastic materials. Both solid and liquid foods are preserved on a very large scale by this method. Next in importance is the drying or dehydration method. Sun-drying is extensively employed in many parts of the world to dry a variety of fruits and vegetables and sometimes fish and meat. Dehydration or artificial drying of fruits and vegetables is extensively employed, and many improvements have been introduced to obtain dried products of excellent quality. Low temperature drying, freeze-drying, accelerated freeze-drying foam-mat drying, etc. are refinements in the technique of dehydration. Freeze preservation, which is an extension of the well-known method of increasing the storage life of fresh fruits and vegetables, and similar other fresh food-stuffs, is extensively employed more in the case of fish and meat, although it is being employed to a limited extent in the case of some fruits and vegetables such as peach, pear, peas, beans, etc. With the introduction of deep-freeze cabinets at home and facility for transport in the frozen state and the resulting convenience to the housewife, this method of preservation is likely to develop rapidly in the near future, especially in the more advanced countries, with a highly sophisticated way of living It cannot, however, completely substitute or replace the conventional canning of foods which, in spite of its drawbacks, continues to hold the field on account of its numerous advantages and conveniences. Preservation by addition of sugar and application of heat is a highly important method in the case of fruits which are utilized in a very large quantities to make jams, jellies, marmalades and preserves. This method is simple, cheap and easy to adopt, and hence its universal popularity. The use of chemical additives, which are permitted as harmless, within limits is fairly widespread in the case of a variety of squashes,
4
PRESERVATION OF FRUITS AND VEGETABLES
cordials and other beverages. At present, only sulphur dioxide and its salts and benzoic acid and some of its ester derivatives are permitted in foods. Sorbic acid or sorbates are also permitted only in some cases. Product of bacterial origin such as nisin, tylosin, etc. are still in the screenÂŹ ing stage. A large number of other chemicals such as formaldehydes, bromo-acetic acid, salicylic acid, etc., which were once used as preservaÂŹ tives, have now been prohibited in foods on account of their harmful
nature. Preservation by fermentation is a very ancient and well-known method. Yeast-fermented fruit wines, which contain ethyl alcohol as a hatural preservative, have been prepared and used for hundreds of years. Such alcoholic liquids undergo further acetic acid fermentation into vinegar, which is an acidulant and is widely employed in pickling. Other wellknown fruit wipes besides grapewine are apple cider, berry wines, etc. Preservation by salting or brining of vegetables such as cucumber, cabbage, bamboo shoots etc., and of unripe fruits such as those of mango, lime, lemon, etc,, is very common in many parts of the world where Indian pickles are well known. Sometimes, pickled vegetables, onion etc., are preserved in clear vinegar to get products having attractive appearance. Such vinegar pickles are highly prized in western countries. Preservation of fruits and vegetables by application of U.V. and ionizing radiation is of recent origin. There is considerable interest in this technique, especially in view of the fact that cheap sources of irraÂŹ diation have become freely available as a result of development of atomic energy installations in some parts of the world. Although, the results appear to be promising, it will take quite sometime before it could be guaranteed as completely harmless and free from any health hazard. There is, however, a great deal of interest at present in the subject. In the present book, emphasis has been placed on those methods and techniques of preservation of fruits and vegetables which have wider application and greater impact on the economic' feasibility and large-scale development of the fruit and vegetable preservation industry. The scope for application of the newer and less known methods of preservation has also been highlighted, wherever they appear to be promising. CANNING AND BOTTLING FRUITS AND VEGETABLES
It is a common experience that fruits, vegetables, meats, and many other articles of food spoil rapidly unless specially cared for. Various methods for preserving these, such as pickling in salt or vinegar, drying, smoking, preserving in sugar or honey etc., i have been developed since time immemorial. Canning is, however, comparatively a modern technique. It developed under the stress of war conditions towards the close of the 18th century. During Napoleonic wars, the French Govern-
PRINCIPLES OF PRESERVATION
5
merit announced a prize of 12,000 Francs for the discovery of a satisfactory
method of preservation so that food could be transported to the fighting forces over long distances without spoiling. In 1810 Nicholas Appert, a Paris confectioner and distiller invented a process for preserving foods in glass containers, took out a patent for his process, and won the prize. He also published a book “The Art of Preserving Animal and Vege¬ table Substances for Many Years”, which is the first known work on modern canning. In honour of its discovering canning is still known as ‘Appertizing’. Appert packed his food in glass containers, added sufficient water to cover the food, placed the corks loosely on top and heated the containers in a water-bath to obtain a temperature of 87°C to 100°C at the centre of the containers. The containers were sealed fairly air-tight by driving in the corks. By this method, he succeeded in preserving several kinds of foods. He ascribed this preserving action to the exclusion of outside air. Gay-Lussac, who studied Appert’s process at the instance of the French Government, concluded that spoilage in foods was essentially a process of oxidation which could be prevented by the exclusion of air from the container. This hypothesis was universally accepted till the time of Louis Pasteur who provided correct explanation of the change through his dis¬ covery of microbes, round about 1860. By his experiments on heat treat¬ ment, he proved that micro-organisms are the real cause of spoilage and that by destroying these, foods can be preserved in suitabje containers. He introduced the word ‘Pasteurization’, which means heat-treatment of food at a sufficiently high temperature to kill the majority, though not all, of the micro-organisms, such as bacteria, moulds and yeasts present in food, water and air and by preventing their access to the food inside the container by sealing it hermetically. In England, Thomas Saddington, who had picked up the general principles of the method of Appert while travelling in France was the first to describe the method of canning of foods in 1807. According to Bitting, Peter Durand (another Englishman) obtained in 1810 the first British Patent on canning of foods in tin containers. Canning of fruits on a commercial scale was introduced in the United States of America in 1817 by William Underwood the founder of the present William Underwood Company of Boston, Mass., who had learnt the technique in London. The Civil War in America and later the Boer War and the Great European War of 1914, with their enormous require¬ ments .of preserved foods, gave a great impetus to the canning industry. The Second World War provided a further fillip and the canning industry witnessed unprecedented development in both technique and scope. At present, the variety and range of canned foods is enormous. Over 350
—
6
PRESERVATION OF FRUITS AND VEGETABLES
different kinds of canned foods are to be found nowadays. The total pack of the major producing countries of the world, even as far back as 1935, has been estimated at 6.5 million tonnes. According to the Canning Trade Almanac 1954, in the U.S.A. alone in 1952, the total production of canned fruit and vegetable products of all categories was of the order of 7 million tonnes. This has further increased tremendously in recent years in the U.S.A. as well as in other major producing countries. Newer techniques and newer products have been introduced. PRINCIPLES OF FOOD PROCESSING
The fundamental principle of preserving foods by heat is known as heat in varying ‘Processing’. It consists basically in the application degrees to the food in closed containers, for a sufficiently long time to sterilize the contents before these are hermetically sealed. The method of processing varies from food to food. In the early days of canning, the ‘open-bath’ processing in boiling water was the one commonly used. This was also the method adopted by Appert. By this method, fruits which were naturally acidic, and more acid vegetables like rhubarb and tomato, could be satisfactorily pre¬ served as most of the spoilage organisms present in them were easily destroyed at the temperature of boiling water. Non-acid vegetables how¬ ever, required processing at higher temperature to get rid of the more resistant organisms present in them. In earlier times, prolonged pro¬ cessing in boiling water for 5 to 6 hours, or heating the canned food for short periods on 3 to 4 successive days to sterilize the product completely, was adopted in the case of non-acid vegetables. This was, however, cumbersome. In 1861, Issac Winslow used calcium chloride in the openbath to raise the temperature as high as 121°C. Calcium chloride, how¬ ever, discoloured the tin can and made it look unattractive. In 1873, a pressure cooker or retort, in which steam is let into a closed vessel under pressure, was invented by A. L. Shriver, a canner of Baltimore. This was a big step forward in the technique. Several improvements have since been introduced in this highly useful equipment. Pressure cookers are now available in various designs and capacities to suit different require¬ ments. Some of them can operate continuously for processing foods under pressure. The original sample ‘open-bath’ method also has been improved greatly. The continuous-type open cooker is a notable addition. In earlier days the cooker consisted of a long iron or wooden tank, sometimes as long as 30 metres containing boiling water through which sealed cans were moved in crates suspended from a moving over-head conveyor. These being bulky and inconvenient, continuous agitating sterilizers were
PRINCIPLES OF PRESERVATION
7
introduced. In these, the sealed cans were conveyed on a continuous belt passing through a closed steam chamber with a device to constantly roll and agitate the cans. Bitting estimates that in these sterilizers the pro¬ cessing time is reduced by as much as 75 per cent. These sterilizers are in common use in many of the modem canneries. A recent innovation is the introduction of the spin-pasteurizer in which the cans rotate on their own axis during pasteurization as well as subsequent cooling. This type of pasteurizer, first developed in Australia, has been found highly useful in the canning of pulpy and viscous materials such as passion fruit pulp, which have a mild flavour easily affected by strong heating for even short periods. The rock-and-roll type of pasteurization in an open cooker has been found satisfactory in the case of canned orange segments, which have a delicate flavour easily adversely effected by longer heating as in conventional stationary processing technique. Hydrostatic cooker where the can travels through a column of water is a more recent introduction to processing techniques. In the case of spin-processing of even viscous materials, the time can be very short. For instance spin-processing is possible for fruit pulp like mango pulp, tomato paste, fruit purees, concentrates, syrups, canned fruits, juices and ready-to-serve beverages (Pruthi, 1962). It has also been reported (Pruthi, 1963) that in case of passion fruit juice employing a rotation of 150 rpm, atmospheric steam at 96°C to 97°C and the time of spin heating for safe canning can be as low as one minute, the time of spin-cooling being 1£ minutes, at 150 rpm under sprays of water at the rate of 45 litres per minute. There is much scope for extending this type of processing to a variety of other heat-sensitive viscous products like custard apple pulp, mango pulp etc.
CHAPTER 2
COMMERCIAL CANNING BEFORE dealing with the various processes involved in the canning of fruits and vegetables on a commercial scale, it is necessary to consider certain important factors such as investment, site, building, water supply, staff, labour, etc. which are essential for the successful running of a large-scale cannery.
Investment The capital outlay includes investment on land, factory building and machinery. The running or operational expenses include the cost of raw material, labour, processing, storage, transport, and distribution. As a first step, the entrepreneur should plan carefully the type and size of proÂŹ duction which would be most advantageous. He should then decide about the plant and other requirements. Factory Site
In selecting site for the factory, the following points should be conÂŹ
sidered carefully :
1. Adequate quantities of the right type of fruits and vegetables should be readily available in the locality, because fruits and vegetables are highly perishable and deteriorate in long distance transport. 2. There should exist proper transport facilities for the movement of raw materials and finished products. 3. The environment should be clean and free from debris, dust etc., as far as possible. The site should be at a considerable distance from other industrial factories spreading soot, smoke, and disagreeable odours, which would affect adversely the quality of the canned product. There should also be facilities for disposal of the cannery wastes. 4. There should be scope for future orderly expansion of the factory. Factory Building
The factory building may be single-storeyed or multi-storeyed. Where the plant is a comparatively small one and works for short periods during the year* a single-storeyed building of light construction will do. In the case of larger plants, that have to run almost throughout the year, multi-storeyed construction is desirable as it would facilitate and cheapen the movement of raw as well as finished products. Flooring should be firm and of good cement to withstand the constant use of water and the
9
COMMERCIAL CASING
movement of heavy-wheeled trucks. A slope of about one quarter of an inch per foot is necessary for proper drainage. All doors, windows and ventilators should be provided with fine wire-gauze to prevent entrance of flies, wasps and other insects. The roof of the building should be high and well ventilated to provide outlet for vapours and steam. The windows should have large glass panes, and part of the roof should be of ground glass to permit a gentle light inside. There should be provision for effiÂŹ cient artificial lighting as the cannery will have to work at night quite often. A sufficient number of dressing and toilet rooms should be provided separately for men and women workers in the factory premises. The workers should be taught the importance of personal hygiene. These are important considerations for handling food-stuff's for human consumption.
I 3| 5
JUICE
STORE
LABELLING AND PACK ING
ROLLER ROOM
GWD'
CELLARY
-S-
i3
LABORATORY
OFFICE
P
CANNING LINE
3lllCE PLANT
J
SUGAR STO ROOM
OIL EXTRACTION ROOM
STORE ROOM
FRUIT RECEIVING AND WASHING
Fig. 1. Plan of a fruit preservation factory
Water Supply and Drainage There should be abundant supply of potable water. Large quantities of water are required for cleaning fruits and vegetables, making syrup and brine, washing floors and machinery, etc. The water system should work at sufficiently high pressure so that supplies can be made at different points in the cannery without a break. The water should not be alkaline or very hard, and should be free from organic matter. Presence of iron and sulphur compounds in it renders it unsuitable for making syrups or brines. Saltish water should be avoided as it would affect the
10
PRESERVATION OF FRUITS AND VEGETABLES
taste of the products. If supplies of the desired quality are not available it would be necessary to instal a water softening plant. Further, the boiler feed water requires ion-exchange treatment to bring it to the desired pH and freed from scale-forming ions,
"Ij
!|EMsÿECsANt MÿAND SEAMER
a HO
£
! i IP 1$| j £
KJING
CAN STORES
AND
BODY
REFORMER FLANGER
.
COOKING TANK i(4) COOLING TANK
I
ITsEAMER~"
CONTINUOUS WATER EXHAUSTER JACKETED
.
KETTLES ,
Fig. 2.
jI
{MEtrai# - j_ (3)
"[!!
PROCESSING""S" RUPERÿ
(1!
I
CANNING LINE
1m33
rr~j
F UIT PAC
' FILLED
Njrxia
(2) RETORT
SYRUP MIXING TANK
BOILER ROOM FUEL STORE
Layout of a canning line
Labour
AH the workers in the factory, whether employed on regular basis or recruited during rush periods, should have clean clothes and aprons to ensure hygienic conditions. They should be medically examined at regular intervals as a precaution against infectious diseases. An efficient system of chemical and microbiological control at various stages of the manu¬ facturing process should be maintained to guard against the risk of con¬ tamination and food-poisoning. There should be a trained chemist with assistants to supervise the work and to ensure the desired standard of production MACHINERY AND EQUIPMENT
Great care is needed in the selection of machinery and other equip¬ ments. Different types of units are in use, but every manufacturer will have to determine his own requirements. However, as a rough guide, layout plant of a small fruit preservation factory with a canning line having output of about 2,000 A 2£ cans per day and a juice plant with a capacity of about 1,000 bottles are given in Figs. 1, 2 and 3.
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