Kai Lab: Food Technology

You need: chopping board on a damp cloth · small serrated knife · banana, cucumber, carrot · apron

1. Put a damp cloth under the board so it can't slide.
2. Bridge: make an arch with your thumb and fingers over the food, and cut down through the gap.
3. Claw: curl your fingertips under, knuckles forward, and slice beside your knuckles.
4. Start with a banana, then cucumber, then carrot.
5. Carry a knife pointing down beside your leg, and never try to catch a falling knife.

How you'll know: You can slice a carrot into even rounds with your fingertips tucked away the whole time.

Safety: Adult demonstration first; about one adult to eight students; knives stay on the board; report any cut straight away.

Go further: Time yourself slicing ten even rounds, then try to beat it without losing the claw.

You need: one apple · lemon juice · salt water · plain water · four labelled saucers · timer

1. Cut the apple into eight equal slices (bridge grip).
2. Dip two slices in lemon juice, two in salt water, two in plain water, and leave two plain.
3. Photograph them at 0, 10, 30 and 60 minutes.
4. Rank them from least to most brown.

How you'll know: You can explain that cutting lets air reach chemicals in the fruit, and acid slows the browning reaction.

Safety: Check for fruit allergies; tasting only if your teacher allows it.

Go further: Try pineapple juice or honey water. Is it the acid, or something else?

You need: apples or feijoas · kitchen scale · baking paper and oven tray or a dehydrator · oven gloves

1. Slice the fruit thinly and evenly (about 3 mm).
2. Weigh the slices together and record the fresh weight.
3. Dry at a low temperature (about 60 to 70°C) for several hours, with an adult managing the oven.
4. Weigh again when leathery and dry.
5. Water lost (%) = (fresh weight − dry weight) ÷ fresh weight × 100.

How you'll know: You can say what percentage of the fruit was water, and explain why dry food keeps longer.

Safety: Only adults put trays in and out of the oven; use oven gloves; let trays cool before touching.

Go further: Compare thick and thin slices. Which dries faster, and which tastes better?

You need: clean glass jar with lid · carrot, cucumber or cauliflower · vinegar, water, salt, a little sugar · pH strips (optional)

1. Wash the jar in hot soapy water and let it air dry.
2. Cut vegetables into sticks and pack them in the jar.
3. An adult heats equal parts vinegar and water with a little salt and sugar until dissolved, then pours it over.
4. Cool, put the lid on, label with the date and keep it in the fridge.
5. Taste and test crunch on day 1, 3 and 7.

How you'll know: You can explain that the acid makes it too sour for most harmful bacteria to grow.

Safety: Adults handle hot liquid; fridge pickles stay in the fridge and are eaten within a few weeks.

Go further: Try different vinegar strengths and record crunch and flavour. Which is still safe?

You need: cabbage · kitchen scale · salt · large bowl · clean jar · a small clean weight (a smaller jar of water) · pH strips

1. Shred the cabbage and weigh it. Work out 2% of the weight: that's how much salt to add.
2. Massage the salt in for about ten minutes until juice comes out.
3. Pack it tightly into the jar so the juice covers it, and weigh it down.
4. Cover loosely and keep at room temperature. Look and test pH every day for a week.
5. Record bubbles, smell, colour and pH. When it tastes sour enough, move it to the fridge.

How you'll know: Your pH readings drop over the week as lactic acid bacteria make acid, and you can explain why that keeps other microbes out.

Safety: Keep the cabbage under the brine; throw it out if you see fuzzy, pink or black mould, slime, or it smells rotten. Teacher decides on tasting.

Go further: Find out how rēwena bread's potato 'bug' or kimchi uses fermentation, and compare with your jar.

You need: small samples in cups with three-digit codes · water to rinse · five-face score sheets · allergy list

1. Give each sample a random three-digit code so tasters aren't influenced by names.
2. Serve samples in a different order to each taster.
3. Tasters sip water between samples and score appearance, aroma, taste, texture and overall on a five-face scale.
4. Ask one open question: 'What would make it better?'
5. Put the scores in a table and find the median for each attribute.

How you'll know: Your results show which attribute to improve, and nobody knew which sample was which.

Safety: Check every taster's allergies first; single-use spoons; tasters can say no.

Go further: Draw a sensory profile (spider diagram) of your product and a shop-bought one on the same chart.

You need: six to eight real food packets (clean and empty) · highlighters · allergen list

1. Find the ingredients list. It is written in order of weight, biggest first.
2. Highlight the allergens. In New Zealand they must be named and shown in bold.
3. Find the 'Contains' summary statement and any 'may contain' warning.
4. Check: would this be safe for someone allergic to milk? To sesame? To wheat?

How you'll know: You can find every allergen on a label in under a minute and explain what 'may contain' means.

Go further: Design an allergy-friendly version of your product for someone who can't have one of your ingredients.

You need: kitchen or bathroom scale · buckets · gloves · tally chart

1. Choose one place: the school orchard, a whānau feijoa tree, the canteen or lunchboxes.
2. For five days, collect and weigh the food that would be thrown away.
3. Sort it: could be eaten, could be preserved, only good for compost.
4. Graph the results and work out a week's and a term's total.

How you'll know: You have real numbers for how much food could be saved, and a plan for some of it.

Safety: Gloves for handling waste; wash hands afterwards; don't eat fallen fruit without washing and checking it.

Go further: Scale your numbers up to the whole town using Love Food Hate Waste ideas.