A Few Questions About "Browning" of Fruits

What is “browning” and how does it happen in fruits?

Enzymic browning occurs in fruits and vegetables from bruising, peeling or cutting. The flesh that is exposed can turn yellowy-brown, all the way to black, this pigment change can occur quite fast and is unappealing to consumers. Browning of fruits occurs due to naturally occuring phenolic compounds being oxidised by enzymes that would normally not directly be exposed to oxygen, the enzymically oxidised flesh then produces a change in colouration due to Quinone compounds (Brown & Hall, 2008). A study in 2018 (Deng, Yang, Capanoglu, Cao & Xiao, 2018) showed that atmospheres with low O2 pressures had less enzymic browning occur than those with higher O2 environments. This indicates that the presence of oxygen with the enzyme, are key factors of browning. Browning in fruits is due an imbalance of oxidative and reductive processes because of the exposure of oxygen to open wounds.

Is there a difference in browning between the slice and the wedge fruit pieces and why?

There is a difference between wedged and sliced pieces of fruit. The wedges samples would have a lower surface area to volume ratio compared to the slices of fruit. That being the case although they are different cuts, the results show very similar trends. Most cuts got duller after the 120 minutes and more yellow in colouration than the 0 minute control.

Is there a difference in between apples, ripe and unripe banana and why?

Ripe bananas contain around 1% starch but when over ripened they contain none, unripe bananas have a higher percentage of starch as it has not yet been converted into sugars. Making unripened bananas very starchy and not sweet (Marriott, Robinson & Karikari, 1981). Apples however are not completely composed of starch; the carbohydrates that compose apples create rigid structures that help retain the shape of the fruit, water goes in and out of cells of the apple and gives it a juicy texture (Quadram Institute, 2018).

Does Citric Acid affect the browning and explain why?

In table 1 citric acid did have an affect on the products, not all the same however. The apple pieces were both quite similar in terms of brightness when compared to the original control readings, it did get slightly darker with more of a yellowish appearance. Even though both apple samples did this, the citric acid apples showed less change than the apples that had nothing applied. The citric acid on both ripe and unripe banana wedges seemed to have been significantlly worse that without the acid in terms of lightness and darkness. As previously stated in question 1, browning occurs when to naturally occuring phenolic compounds being oxidised by enzymes that would normally not directly be exposed to oxygen, making enzymes an essential role in browning. If the environment was to change pH to where the enzyme would not be able to tolerate/ function, meaning that the citric acid is at a low enough concentration where there is loss of enzyme activity( McCORD& Kilara, 1983).