In the banana, I agree that less saturation would help, but more contrast isn't necessarily needed. The banana cools down to green in the shadow, which is to be expected with a blue ambient atmosphere, but if the surface it's resting on is warm, this will have an effect.
I do have to commend you for trying to objectively portray the fruit. Although you might otherwise find yourself coerced into painting what you think you know is there, painting what you think you see will go towards your autonomy in making the right color selections.
Technique-wise, the apples are too convoluted, and although you might be portraying the texture with your brushwork, applying the texture as a superficial detail might have been more appropriate. Also, the white highlight looks to cool as it gets diffused.
Good on you, and let's see more. | 
