Fruit waste materials

The biopolymers in fruit waste can be used to create flexible, translucent, leather-like materials. Below two mango recipies, one including starch. Try variations using overripe pear, fig etcetera.

Overripe Mango Leather #1

  • 1 Overripe mango - with skin get these as waste from the market, they can have dents and bruises it doesn't matter. We will dehydrate the mango until it becomes leather-like.
  • Potato starch - 1 tbsp (10 g) functions as the polymeer (makes the mango puree harder)
  • White vinegar - 1 tbsp (8 gr) vinegar is almost always added to starch-based biopolymers to change the molecular structure of the starch, making it stronger and more workable
  • Salt - 5 gr as a preservative and stabilizer.
  • Vegetable oil - 1 tbsp as a release agent for the mould.
    Method
    1. 1.
      Preparation
      • Cut the mango into smaller pieces and puree it in a blender or with a mixer.
      • Optional: Prepare the mold by applying some oil
      • Dissolve the starch in a dash of water until liquid
    2. 2.
      Mixing the ingredients and activating the starch
      • put the mango puree in the pot with the salt and vinegar
      • heat it at a low heat while stirring, you don't want it to boil and stick to the pot, but you want to kill any bacteria in there and dissipate some water.
      • dissipate some of the excess water if it is very liquid but keep a low heat and stir.
      • add the starch mixture and continue to stir for at least a minute until it transforms into a thick paste. If the paste is too liquid it will shrink a lot during the dehydration process and your leather sheet will tear.
    3. 3.
      Casting and dehydrating in the oven
      • Pour the paste onto the surface or mould and spread it out evenly, knock it on a hard surface gently to even it out more.
      • Heat the oven to 50 degrees Celcius on the fan setting and put the paste into the oven for at least 16 hours (you can spread it out over a few days with airdrying in between). If your oven allows it without turning itself off: keep the door slightly open with a cloth to let the moisture escape).
      • Carefully peel thea leather off the tray, flip it, and check if the bottom has fully dried. If not, put back in the oven with the moist side up for another few hours.
      • Optional: you can airdry the leather as well, but there is some more risk of molding. Don't dry it in direct sunlight.
    4. 4.
      Air drying
      • when the leather is dry to the touch (it will be a bit darker of color now), let it airdry in a well-ventilated space for another 5-7 days.
      • alternate drying and pressing under a stack of heavy books or dry on a roster with weight on top for further drying while keeping it flat.

Overripe Mango Leather #2

Ingredients

  • 2 Overripe mangoes - with skin get these as waste from the market, they can have dents and bruises it doesn't matter.
  • 1 lemon
  • Beeswax: 20g
  • Cinnamon: 1 teaspoon

Method

  1. 1.
    Preparation
    • Cut the mango into smaller pieces and puree it in a blender or with a mixer
    • Cut the beeswax in smaller pieces
  2. 2.
    Mixing the ingredients
    • put the mango puree in the pot with the lemon and wax
    • heat it at a low heat while stirring, you don't want it to boil and stick to the pot, but you want to kill any bacteria in there and dissipate some water.
    • dissipate some of the excess water if it is very liquid but keep a low heat and stir. -after 20 minutes the mixture should be thick but liquid enough to cast on a flat surface
  3. 3.
    Casting and dehydrating in the oven
    • Pour the paste onto the surface or mould and spread it out evenly, knock it on a hard surface gently to even it out more.
    • Heat the oven to 50 degrees Celcius on the fan setting and put the paste into the oven for at least 16 hours (you can spread it out over a few days with air drying in between). If your oven allows it without turning itself off: keep the door slightly open with a cloth to let the moisture escape).
    • After one day out the oven, carefully peel the leather off the tray, flip it, and check if the bottom has fully dried. If not, put back in the oven with the moist side up for another few hours.
  4. 4.
    Air drying
    • when the leather is dry to the touch (it will be a bit darker of color now), let it air dry in a well-ventilated space for another 5-7 days.
    • alternate drying and pressing under a stack of heavy books or dry on a roster with weight on top for further drying while keeping it flat.

Drying/curing/growth process

  • Mold depth: 3 mm (using acrylic borders)
  • Shrinkage thickness: 50 %
  • Shrinkage width/length: 5%
Shrinkage and deformation control
Letting it dry up to 7 days to get to the final form. Mango leather tends to dry at a different pace every time, depending on the amount of juice and amount of dissipating. This is a slow process. Trying to demould too quickly will damage the leather.

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