The colours of my apple sauces

My apple sauces made with unpeeled organic garden apples are healthy and nutritious… and it shows!

 

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In 2012, I asked myself: if I cook apple sauce without peeling the apples, will the skins colour it? I had already noticed the slightly pink colour of an apple sauce I made with unpeeled red-orange apples given by one of our London neighbours. I took the question further: how would the colours compare if I made several apple sauces at the same time with apples of different colours?

I decided I would cook three apple sauces and then compare the results. I bought three different types of standard commercial apples in a local supermarket: green Granny Smith and two other varieties of a deep ruby red and an intense yellow.

Les pommes du commerce achetées pour mon expérience 2012.

The commercial apples bought for my 2012 experiment. Photo October 2012, London, UK.

I made the apple sauces as follows. After cleaning the apples in water, I removed the stem and the calix (the rest of the flower at the bottom of the apple) with the tip of a knife, cut into pieces and stewed for ten to fifteen minutes from boiling point in a saucepan with some water. The peels and seeds were then separated in a food mill with a fine grid so that we ended up with a soft puree ready to eat after cooling.

Moulin à légumes

Food mill, with a mid-size grid. Photo 7 November 2020, Sussex, UK.

I probably added some sugar to the saucepan, around 100g per kilo of fruit, as I used to at the time. I must say that in France, apple sauce, which we call compote, is mostly eaten as a dessert. I mention the sugar because it makes the colour of a jam brighter and more transparent. The difference is easily noticeable when we compare for instance a traditional British strawberry jam to one reduced in sugar. I hadn’t added the sugar to the sauces to that aim, however it might have made them more aesthetically pleasing to the eye.

I found the result convincing: the colours were quite distinctive. Only the Granny Smith had significantly changed colours, the compote turning yellowy through cooking, losing the original bright spring green colour of the apples’ skin. It still looked greenish next to the others.

Trois couleurs de compote de pomme

The yellow, red and green apples became yellow, red and greenish apple sauces. Photo October 2012, London, UK.

2020 experiment

My 2012 London experiment was conclusive. The skins of the apples coloured the sieved apple sauces and the contrast in colours was even more obvious when the sauces were looked at next to each other.

I repeated the experiment this autumn, this time in Cantal, France, with fully organic garden apples.

As in 2012, I looked for green, red and yellow apples. Choosing the yellow ones was easy. I used apples from our orchard which I knew would make a very yellow and tasty apple sauce. There was no need to add sugar. I didn’t add any to the apple sauces this time.

We don’t have apples of a deep ruby red. However, one of our trees, probably of the Reine des reinettes cultivar, produces red-orange apples when fully ripe. I selected those, grown in direct sunlight, of a bright red over around three quarters of their skin. Would the apple sauce be pink? The pink turned out to be more intense than I expected.

As for the green apples, we don’t have any in our orchard. I used apples we picked a fortnight earlier in a conservation orchard of heritage varieties, in which the apples grow, as in ours, without any other human intervention than some maintenance pruning.

Les pommes de jardin non traitées utilisées en 2020.

Fully organic garden apples were used in 2020. Photo 24 October 2020, Cantal, France.

Unsurprisingly, the same causes produced the same effects. The apple skins significantly coloured the apple sauces. The spring green turned greenish, even slightly brown this time. I could have obtained a colour closer to the original in this third sauce. Adding some lemon juice in the pan and reducing cooking time would have enabled me to keep a bit more of the green.

The colours of the three apple sauces

The colours of my 2020 apple sauces.

Aesthetics and nutrition

In 2012, my interest was purely aesthetic. I replicated the experiment in 2020 with a different mindset. I thought that not only the apple sauces could be attractive and pleasant to the eye, but also that their colours could convey a meaningful message, that of a nourishing product. I have long heard that apple skins are full of nutrients. I asked myself: if the apple skins colour the sauces, don’t they also make them more nutritious?

The research articles I found enabled me to validate this hypothesis. Not only the apple skins are rich in healthy nutrients, but also part of these nutrients pass into the apple sauce when it is made without peeling the apples. Several studies have come to this conclusion, including one carried out in 2014 by INRAE, the French National Research Institute for Agriculture, Food and Environment1 in collaboration with the University of Avignon2.

‘Polyphenols and carotenoids are among the most ubiquitous secondary metabolites in fruit and vegetables’ (Renard et al, 2014, p 126). According to the authors, many studies have highlighted the health benefits of these micro-nutrients (p 127). They focused on apples as a case study, mentioning they are rich in polyphenols, with higher concentrations in the skin than in the flesh (pp 130-131).

The Harvard T.H. Chan School of Public Health have mentioned the presence of pectin in apples, a soluble fiber, and listed its health benefits. They also said that ‘Fresh, whole apples offer the most nutrients. Discarding the skin removes much of the fiber and the majority of flavonoids.’3 (flavonoids are a type of polyphenols). Finally, regarding vitamins, minerals and other micro-nutrients, Interfel, the French professional body for the fresh fruit and vegetable sector, inform consumers that apples are relatively low in calories but their skin contain a lot of vitamins and minerals. They advise to wash the raw apples under water and to munch on them unpeeled.4

This is true not only for raw apples, but also for cooked ones. When processing fruit using heat, ‘The more detrimental steps are actually those that involve physical actions to separate peels from flesh (screening, peeling), because of higher concentrations of secondary metabolites in the epidermis’ (Renard et al, p 125). The study focused on polyphenols and carotenoids. Muriel Colin-Henrion’s research proved that it is also true for pectin. She wrote in the conclusion of her thesis on apples that cooking the fruit uncored and unpeeled is essential to keeping part of its components of nutritional interest in the final product (Colin-Henrion, 2008, p 251).

“CQFD!” (QED, quod erat demonstrandum), I told myself like a mathematician pleased that his theory was proven right. It seemed obvious to me that an apple sauce made with sun-ripened garden apples is more nourishing when it has been made with the apples unpeeled. I now have scientific evidence to support my claim.

We could take the analysis further and look at the preservation of vitamins during cooking. While seeking for scientific evidence of this, I will direct the reader to the numerous publications of nutritional advice that can be found in the French press. They indicate that stewing the fruits in their water preserves a good part of their vitamins. This is what I did in my 2012 and 2020 experiments, cooking the apples for a short time (10 to 15 minutes) and covering the saucepan with a lid to avoid evaporation.

We could also look more closely at the connection between colour and nutrition. We know for instance that the pink colour of an apple sauce or juice signals the presence of anthocyanins, one of the categories of polyphenols good for health. This correlation between colour and nutrition has been mentioned in several studies, in particular an article from the University of Pennsylvania on apples with a red skin5 and the INRAE / University of Avignon study (Renard et al, 2014, p 126 and p 130).

However, we need to avoid jumping to conclusions. For instance, an apple sauce being pink doesn’t mean that it is more nourishing than a standard one. Because the skin contains more nutrients than the flesh, an apple sauce made with peeled red-fleshed apples (yes, red-fleshed apples do exist6) may be pink, however it will be less nutritious than an apple sauce of a standard pale-yellow colour made with unpeeled apples. Therefore we cannot conclude that colour is always a reliable indicator of a highly nutritious apple sauce.

My apple sauces don’t have this problem : I don’t peel the apples when I cook them. Therefore they benefit from the diversity of nutrients of the apples’ skin, which also give them their nice colour. Moreover, in 2020, I used fully organic apples, sunbathed and harvested when ripe in the countryside of Cantal, France. I think I can say that these apple sauces are particularly healthy and nourishing, and that it shows!

 

Bibliography

Colin-Henrion, M. (2008). De la pomme à la pomme transformée : impact du procédé sur deux composés d’intérêt nutritionnel. Caractérisation physique et sensorielle des produits transformés. domain_other. Université d’Angers, 2008. Français. fftel-00351179f
https://tel.archives-ouvertes.fr/tel-00351179/document (in French, accessed 12 January 2021).

Renard, C., Caris-Veyrat, C., Dufour, C., Le Bourvellec-Samour, C. (2014). Le devenir des polyphénols et caroténoïdes dans les fruits et légumes traités thermiquement. Innovations Agronomiques, INRA, 2014, 42, pp.125-137. hal-02629481
https://hal.inrae.fr/hal-02629481/document (in French, abstract in English, accessed 12 January 2021).

Internet sources

  1. https://www.inrae.fr/en/about-us (accessed 12 January 2021)
  2. https://www6.paca.inrae.fr/sqpov_eng/Home/EDITO (accessed 12 January 2021)
  3. https://www.hsph.harvard.edu/nutritionsource/food-features/apples/ (accessed 12 January 2021).
  4. https://www.lesfruitsetlegumesfrais.com/fruits-legumes/fruits-a-pepins/pomme/nutritions-et-bienfaits (in French, accessed 12 January 2021).
  5. https://extension.psu.edu/fruit-color-promoting-red-color-development-in-apple (accessed 12 January 2021)
  6. https://www.sciencedirect.com/science/article/pii/S1756464614002047 (accessed 12 January 2021).

 

 

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