These are flashcards an notes made by students on topics like 'coating', 'hydrophilic' and 'lipid', originating from:

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- Wageningen University
ISBN-13 9990002019708
665 Flashcards & Notes
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Study Cards on coating, hydrophilic, lipid

The water vapour permeability rises very quickly with increasing relative humidity? What are 2 reasons of that?
  • Increasing sorption
  • More moisture in the film, the moisture molecules diffuse much more quickly (plasticising effect of water)
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What is the difference in permeability through a hydrophobic component and a hydrophilic component?
The permeability of water through a hydrophobic component such as lipids, is lower than through a hydrophilic component such as proteins.
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What coating material and what medium would you choose for coating apples to reduce moisture loss?
Dipping or spraying with wax
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What coating material and what medium would you choose for coating 'croutons' that need to stay crispy for some time in hot soup?
Spraying with a molten fat
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What coating material and what medium would you choose for a ready-made sandwich with jam, to be sold at petrol stations?
Mechanical application of butter or peanut butter, probably even by hand
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What coating material and what medium would you choose for coating a pellet to reduce dust formation during handling?
To evacuate the pellets, then immerse them in an oil, and then releasing the vacuum. The oil penetrates into the pores. So, the barrier is not just a film on top of the pellet, but is also plugging the pores.
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One of the ways to obtain high-quality dried fruit is to first coat them, and then immerse them for some time in a bath having a very low water activity - this is called osmotic drying. The fruit loses a significant part of its initial weight during the process. The advantage of using a coating is that components other than water cannot pass the coating easily and are retained better in the fruit. This leads to a better end product quality. What type of coating should be used for this process?
You are looking for a barrier through which water passes but flavour molecules cannot pass.
Proteins and carbohydrates are hydrophilic (lipids not) and thus allow passage of water. Here you should keep in mind that the coating does not dissolve in the water bath. So a cross-linked protein layer may be possible, or an insoluble film of carbohydrates with proteins.
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You have developed a new type of corn flakes with which you can make a unique health claim. Unfortunately, you found that when immersed in milk, they almost immediately become soft. Therefore, you want to treat these corn flakes with a coating, such that they will not become soft in at least 5 minutes after immersion in milk. You want to apply a polysaccharides coating with a certain permeability. What mechanism of film formation and what type of application method would you recommend for this coating on this product?
The best application method is spraying the polysaccharide solution onto the cornflakes during rotation in a drum. The solvent will need to evaporate from the sprayed solution during a heating step after which the polysaccharides will remain on the flakes.
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Which type of film does not allow the passage of flavour molecules?
  • Lipid films
  • Protein films
  • Carbohydrate films
  • Composites
Protein or carbohydrate films. A glassy type of material will not allow the passage of large flavour molecules.

Lipid films --> The flavour is relatively non-polar, which means that a lipid may not be a good choice. It will absorb the flavour and readily transfer it to the air.
Composites --> The granule is very small, so applying a composite film would be difficult, as it is difficult to get these defect-free in thinner films
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