From field to harvest to processing
Food doesn’t go straight from the field to your plate. What happens to our food to prepare it for processing, and how is it processed before it ends up in the supermarket?
Many consumers expect to be able to buy a wide variety of fruits and vegetables all year round, such as strawberries in winter. However, many crops are seasonal, and their availability is also affected by factors such as weather conditions. This means growers and food processors have to plan carefully to make sure they’re able to meet consumer demand for a continuous supply of high-quality food.
The timing of the harvest is important. If fruits and vegetables are harvested when they’re too ripe, they will spoil or damage easily. If they’re harvested too early, yields will be lower and the produce could be lacking in flavour and colour or even inedible. Growers need to be able to predict when their crops will reach the perfect stage of maturity. This can be done by monitoring the surrounding temperature, as this is an important factor determining when crops reach maturity, or controlling the temperature of crops in greenhouses.
Once crops are harvested, they’re often delivered to a food processing plant – although some crops don’t make it this far due to quality issues and are thrown away or turned into animal feed. Today, the sorting and packing of products is mostly done by machines. In the See Also section you’ll find some links to videos showing what this looks like.
What qualities do growers and food processors look for in crops?
- Size and shape: will it be easy to handle?
- Colour: will it look appealing?
- Texture: will it be able to withstand processes such as cleaning?
- Functional properties, such as protein levels in wheat: what should it be used to make (bread, cakes, noodles)?
These qualities determine whether crops are rejected or accepted and which processes they go through. Fresh, ripe fruit might undergo minimal processing. Fruit that’s less suitable to be eaten fresh, such as a harder variety of peach, can better withstand intense processing such as freezing, drying or canning.
Travel and storage
The harvested produce usually needs to travel and be kept in storage. Food processors control temperature, humidity and light levels to prevent food from spoiling during transport and storage. Some fruits are harvested before they’re ripe but continue ripening in storage, while others stop ripening after the harvest. Cereals such as wheat are dried before storage, but still need to be protected from mould and pests like insects and rodents.
It’s important to wash food products to remove contaminants, which might be harmful to humans. Common contaminants include leaves, twigs, sand, soil, insects, fungi, pesticides, fertilisers and microorganisms – not things you’d want to eat! Cleaning can be done using water, air, or even magnets to remove metal particles. Fruits and vegetables with rough skin are harder to wash and so the process needs to be more rigorous.
Fruit and vegetables are often trimmed, sliced or peeled before they’re packaged to make them more convenient for consumers. Since these processes are usually done by machines rather than by hand, fruit and vegetables that are unevenly sized or shaped are harder to process and might be rejected.
Are pre-cut vegetables worth buying, or is it better to cut them yourself? In the See Also section we’ve included an article discussing this.
Consumers want their food to look and taste fresh, and judge factors like colour and texture when choosing what to buy. However, fruit and vegetables begin to spoil after the harvest due to several processes, including enzyme action which causes oxidation and leads to browning. This happens even quicker when foods are peeled or chopped. To delay food spoiling, food processors often use preservative treatments such as sulfites added to peeled potatoes, fruit juices and dried fruits and vegetables.
These are just a few of the processes crops undergo. Some are to extend shelf-life and reduce waste, some to improve appearance, some for convenience and some to make food safer. While some people are wary of processed food, others value the convenience, safety and freshness processing brings.
- What are the positives and negatives of seasonal food products being available to buy all year round?
- What qualities do you look for when choosing which fruit and vegetables to buy?
- What are your views on post-harvest processing?
- Do you trust the processes your food goes through before you buy it in the supermarket? Why, or why not?
© University of Cambridge