Meat Science II – SS3 Livestock Farming Lesson Note (Second Term)

Meat processing and preservation are the ways of keeping meat safe to eat for weeks or months after slaughter.

Behavioural objectives

By the end of the lesson, students should be able to:

1. state three reasons for processing and preserving meat;
2. describe the common methods of meat preservation;
3. describe kilishi, suya and sausages as meat products in Nigeria;
4. explain the uses of vacuum packaging, plastic wraps and canning;
5. state the danger zone for bacterial growth and the signs of spoiled meat.

Why do we process and preserve meat?

We process and preserve meat to stop spoilage, keep it for later and add value to it.

• Saving for later: keeps meat safe to eat weeks or months after slaughter.
• Adding flavour: gives products such as suya, kilishi and sausages.
• Making money: a pack of spiced, dried meat often sells for more than a raw chunk of beef.
• Reducing waste: meat that is not sold fresh can be dried, smoked or frozen instead of thrown away.

Why does fresh meat spoil?

Fresh meat spoils because enzymes, bacteria and moulds break it down soon after slaughter.

• Enzymes: natural substances in the meat that start to break down the tissue.
• Bacteria: tiny germs that multiply on the meat and cause bad smell and slime.
• Moulds: fungi that grow on meat kept in damp conditions.
• Warmth and moisture: they help germs grow faster.

• Without any treatment, fresh meat spoils in a day or two in a warm place.
• Preservation makes the meat an unfriendly place for bacteria.
• It does this by removing water, changing the temperature or adding preservatives such as salt.

What are the common methods of meat preservation?

There are four common methods of meat preservation: low temperature, heat treatment, drying and curing.

Low temperature (cold)

• Chilling: keeping meat in a fridge at 0°C to 4°C. This slows down bacteria for a few days.
• Freezing: keeping meat at -18°C or below. The water in the meat turns to ice, so bacteria cannot grow.

Heat treatment (thermal)

• Cooking: heat kills most bacteria, but cooked meat spoils again if left in a warm place.
• Canning: meat is heated at high temperature inside a sealed can to kill spoilage germs.

Dehydration (drying)

Drying removes water from meat, and bacteria cannot grow without water.

• Sun drying: the traditional way to make meat strips last.
• Smoking: meat is dried by heat and smoke from wood. The smoke forms a dry layer on the surface, helps keep germs out and adds flavour.

Curing (salting)

Curing is the preservation of meat with salt, sometimes with spices or nitrates.

• Salt: draws water out of the meat so bacteria cannot grow.
• Nitrates: help keep the meat pink and fresh-looking.
• Spices: add flavour.

How do the preservation methods compare?

The table shows how each method works and gives an example.

What are the popular meat products in Nigeria?

Three popular processed meat products in Nigeria are kilishi, suya and sausages.

What is kilishi?

Kilishi is a spiced, dried meat snack from northern Nigeria, similar to beef jerky.

1. Meat is sliced very thin.
2. The slices are dipped in a spicy peanut paste (labu).
3. The slices are sun-dried.
4. The dried meat is lightly roasted.

What is suya?

Suya is spiced meat grilled over an open fire.

• Spices: ginger and pepper add flavour and help the meat keep for a short time.
• Heat: grilling cooks the meat and dries its surface.
• Storage: suya is best eaten fresh and does not keep as long as kilishi.

What are sausages?

Sausages are ground meat mixed with fat and spices and packed into a casing.

1. The meat is ground up.
2. Fat and spices are mixed in.
3. The mixture is stuffed into a casing, usually made from cleaned intestines.
4. The sausages are cooked or smoked, then kept cold.

Why is meat packaged?

Packaging protects meat from dirt, flies and air, and it also makes the meat look good in the shop.

• Vacuum packaging: all the air is sucked out of a plastic bag before sealing. Without oxygen, most spoilage bacteria cannot grow.
• Plastic wraps: used for short-term sales in supermarkets. They keep dust off but do not stop spoilage for long.
• Canning: the most secure packaging. It protects the meat from air, light and insects for a very long time.

Steps in canning meat

1. Clean the meat and cut it into pieces.
2. Pack the meat into clean cans.
3. Seal the cans tightly.
4. Heat the sealed cans at high temperature to kill germs.
5. Cool the cans and store them in a cool, dry place.

What is the danger zone for meat?

The danger zone is the temperature range between 5°C and 60°C, where bacteria grow quickly.

• A normal room in Nigeria is inside this range.
• Meat should never stay in the danger zone for more than 2 hours.
• Keep raw meat cold and cook it until it is hot all through.

What are the signs of spoiled meat?

Spoiled meat has a bad smell, a slimy feel and a changed colour.

• Smell: a sour or rotten odour.
• Touch: the meat feels slimy or sticky.
• Colour: beef turns green or grey. A little browning can be caused by air alone.
• Mould: fuzzy growth on the surface.

Class discussion and practical exercise

1. The suya test: why do suya sellers wrap their meat in old newspapers or aluminium foil? Which one is more hygienic and why?
2. Observation: visit a supermarket and look at the meat section. Compare a tray of fresh beef with a vacuum-sealed pack of sausages. Which one has a longer expiry date?

Evaluation

1. State three reasons for processing and preserving meat.
2. Explain how chilling differs from freezing.
3. Describe how kilishi is made.
4. Why does vacuum packaging slow down spoilage?
5. What is the danger zone, and how long should meat stay in it at most?

Assignment

Project idea: if you wanted to start a business selling “gourmet kilishi”, state three things you could do to make your packaging more professional than the ones sold on the street. Use the packaging ideas in this lesson.