Week 9: Fruit

Varieties and what distinguishes them, where each is stored and why, how to choose well at the market, ripening treated as a schedulable process, and the fat, protein and calorie content of five fruits common to this course.

19 April 2027

Open the slides

Week 2 separated produce into ethylene producers and ethylene-sensitive produce and stored them apart on that basis. This week returns to the same chemistry from the other side: most of the fruit responsible for that ethylene, examined for what it is doing and when.

Varieties and what distinguishes them#

Fruit divides into two ripening behaviours, and the difference matters more than the difference between any two species. Climacteric fruit — apples, bananas, avocados, peaches and others — keeps producing ethylene and respiring faster after it is picked, which is why it continues to ripen off the plant. Non-climacteric fruit — citrus, grapes, cherries, berries — does not get that second wind: once picked, it is as ripe as it will ever be.

Storage: where, and why#

The climacteric/non-climacteric split, not species, decides where a fruit belongs. Bananas, citrus, mangoes, melons, papaya and pineapple are harmed rather than helped by cold — refrigeration slows or blocks the ripening these fruits still have left to do, so they keep to the counter. Stone fruit, kiwi and avocado ripen on the counter first, then move to the refrigerator once ready. Berries, cherries and grapes are non-climacteric and were as good as they will get at harvest, so refrigeration from the start only slows their decline.

Choosing well at the market#

Ripeness at the point of sale is read fruit by fruit rather than by one rule: firm and unbruised for an apple, fragrant and heavy for its size for citrus, yielding to gentle pressure for an avocado or a papaya.

Ripening as a schedulable process#

Because a climacteric fruit keeps producing the hormone that ripens it after harvest, buying one underripe is not a compromise — it is a way of deciding, rather than discovering, when it will be ready. A non-climacteric fruit offers no such choice: it must be bought at the ripeness it will be eaten at, because none is coming later.

Apple, banana, orange, strawberry and mango: fat, protein and calories per 100 g#

The invent-a-recipe assessment (week 6) asks for a nutritional composition traceable to a named food-composition database; fruit is a common component of that composition and deserves the same treatment as this course has already given vegetables and meat. Figures are per 100 g raw, from USDA FoodData Central, for the five fruits this week’s tutorial exercise draws on: the climacteric fruits here — apple, banana, mango — and the two non-climacteric fruits — orange and strawberry.

The calorie spread across the five tracks sugar content more than anything else discussed this week; none of the five is a meaningful source of fat or protein, which is worth stating so a recipe’s protein total is not accidentally attributed to its fruit component. This week’s tutorial exercise uses the macro calculator on all five of these figures, drawn directly from FoodData Central.

Afterwards#

The connection to week 2 is direct: an ethylene producer stored loose in the same drawer as an ethylene-sensitive vegetable was the problem then; the same gas, examined here as the thing that makes a piece of fruit worth buying early rather than late, is the same chemistry looked at from the other side of the exchange.

Outline#

• varieties: climacteric versus non-climacteric, and why the split matters
• storage: where each group belongs, and why cold helps some and harms others
• choosing well at market, fruit by fruit
• ripening as a process that can be scheduled rather than waited on
• fat, protein and calorie content per 100 g for apple, banana, orange, strawberry and mango, sourced to USDA FoodData Central