Agricultural processing can be defined as an activity performed to maintain or improve the quality or to change the form or characteristics of the agricultural product. Processing operations are undertaken to add value to agricultural materials after their production.
The main purpose of agricultural processing is to minimize the qualitative and quantitative deterioration of the material after harvest.
High post-harvest food losses, arising largely from limited food preservation capacity, are a major factor constraining food and nutrition security in the developing countries of West Africa, where seasonal food shortages and nutritional deficiency diseases remain significant concerns.
Simple, low-cost, traditional food processing techniques form the foundation of small-scale food processing enterprises crucial for rural development in West Africa. It is estimated that about 50% of perishable food commodities, including fruits, vegetables, roots, and tubers, and about 30% of food grains, including maize, sorghum, millet, rice, and cowpeas, are lost after harvest in West Africa.
Ineffective or inappropriate food processing technologies, careless harvesting, inefficient post-harvest handling practices, poor roads, dilapidated rail systems, poor market practices, and inadequate or lack of storage facilities, packing houses, and market infrastructures contribute to high post-harvest food losses in West African countries.
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Fundamentals and Principles of Crop Products Processing
A. Reasons for Food Processing
1. To improve digestibility, making it easier for the body to break down the food while in the stomach.
2. To improve sanitary quality, making it safer to eat by killing harmful microorganisms.
3. To create desirable flavors that are pleasant to the taste.
4. To preserve food, allowing it to be kept over time, saving time and energy.
B. Principles of Agricultural Processing
Food processing includes food preparation (which makes food items ready for immediate consumption) and food preservation (which preserves food items for future use). Food processing may sometimes result in the loss of certain desirable food qualities.
Food preservation can be either short or long term. Short-term preservation is applicable to horticultural commodities that are consumed relatively soon after harvest. For these, the best preservation techniques involve keeping the product alive and respiring.
Short-term preservation does not destroy microorganisms or enzymes; deteriorative reactions, therefore, proceed, often at a faster rate due to the stresses imparted during harvesting and handling operations.
Long-term preservation encompasses the inactivation or control of microorganisms and enzymes and the reduction or elimination of chemical reactions that cause food deterioration. Microorganisms may be controlled through heat, cold, dehydration, acid, sugar, salt, smoke, atmospheric composition, and radiation.
Mild heat treatments in the range of 82°C to 93°C are commonly used to kill bacteria in low-acid foods. However, to ensure spore destruction, temperatures of 121°C wet heat for 15 minutes or longer are required.
Refrigeration and freezing slow microbial growth and may kill a small fraction of microorganisms present in or on a fruit or vegetable, but they do not kill all bacteria.
If all of the water in a product exists in a solid state, the growth of microorganisms will be prevented, but growth would resume at the same rate, or perhaps more rapidly, when thawed. Dehydration removes water required for growth from microbial cells and preserves horticultural crops against microbial deterioration.
Similarly, sugar and salt act as preservatives by causing osmotic dehydration of microbial cells and their eventual death.
Control of moisture or relative humidity (RH) in the storage environment is a crucial factor in maintaining the desired life of horticultural crops while preventing the preservation of microorganisms.
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Types of Agricultural Processing
Agricultural processing can be defined as an activity performed to maintain or improve the quality or to change the form or characteristics of the agricultural product. Processing operations are undertaken to add value to agricultural materials after their production.
The main purpose of agricultural processing is to minimize the qualitative and quantitative deterioration of materials after harvest. Different types of food processing can be categorized into:
1. Primary processing: Purification of raw materials by removing foreign matter, immature grains, and making the raw material eligible for further processing by grading into different lots or converting raw materials into forms suitable for secondary processing.
2. Secondary processing: Processing of primary processed raw materials into products suitable for food use or consumption after cooking, roasting, frying, etc.
3. Tertiary processing: Conversion of secondarily processed materials into ready-to-eat forms.
Food items are marketed in various forms, such as raw, primarily processed, secondarily processed, and tertiary processed. Farmers generally prefer to sell their agricultural produce immediately after harvest, setting it aside for their consumption and seed purposes.
The food processing sector has gained importance due to consumers’ preference for ready-to-cook (RTC) and ready-to-eat (RTE) foods, in addition to the increased demand for snack foods and beverages.
Fundamentals and Principles of Crop Products Storage
Grain Storage Principles
1. Conditions of the Grains:
i. Only clean, unbroken kernels should be selected for storage.
ii. The grain should be dry.
iii. The grain should be cool when placed into storage.
2. Climatic Conditions: Grain stores best in dry and cool weather. Unfortunately, the weather is not always dry and cool. During the rainy season, even well-dried grain can become wet again if exposed to very wet air or rain.
As grain must be stored throughout various weather conditions, the chosen storage method must protect the grain from the worst weather.
3. Store Conditions: A grain store must perform one task: to protect the grain from its natural enemies (molds and fungi, insects, rats, birds, and other animals). For this, the grain store should have the following properties:
i. The store must be dry.
ii. The store should be cool.
iii. The store should block out the sun.
iv. The store should be clean.
v. The store should have no holes or cracks in the roof, walls, or floor.
vi. The store may require insecticide treatment.
4. Store Location: Grain stores should be situated away from potential sources of infestation and from growing crops. Grain and tuber moths are good flyers, and adults from infested stores often infest crops in the field. Separating stores from fields helps reduce the risk of attack.
Dos and Don’ts for Storage of Fresh Produce
1. Do’s:
i. Store only high-quality produce, free from damage, decay, and at proper maturity (not overripe or under-mature).
ii. Follow recommendations for proper temperature, relative humidity, and ventilation for the commodities.
iii. Store boxes on perforated wooden racks designed for air movement.
iv. Provide adequate ventilation in the storage room by maintaining space between stack lines.
v. Monitor the temperature in the storage room with thermometers placed at various locations.
vi. Protect storage rooms from rodents by keeping the outdoor area clean, free from trash, and weeds.
vii. Handle produce gently and always store produce of the best quality.
2. Don’ts:
i. Never store carrots with apples, as apples release ethylene gas, which makes carrots bitter due to the formation of iso-coumarin.
ii. Avoid lower than recommended temperatures in storage, as many commodities are susceptible to freezing or chilling injuries.
iii. Do not overload storage rooms or stack boxes tightly, as this will hinder air movement.
iv. Avoid storing onions or garlic in high-humidity environments.
v. Control the insect, pest, and rodent population inside the store.
vi. Check produce regularly for damage due to insects, pests, water loss, ripening, or shriveling.
It is advisable not to store different crops together in one cold storage room. However, this is often difficult to maintain and, in some cases, unavoidable, especially at distribution or retail levels.
A common practice is to set cold chambers at an average of 2–5°C and 90–95% relative humidity, irrespective of specific requirements.
Frequent opening and closing of cold chambers for product loading and unloading causes temperature increases and a decrease in relative humidity. Therefore, it is recommended to have specific chambers for different crops.
Agricultural processing can be defined as an activity performed to maintain or improve the quality or to change the form or characteristics of agricultural products.
Processing operations are aimed at adding value to agricultural materials after their production. The storage requirements for a variety of crops are diverse, from simple storage needs for cereals to more complex needs for fresh fruits, vegetables, and root crops, which require careful handling to ensure proper storage.
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