browning is the visual sign of spoilage for fruits and vegetables due to chemical reactions.
browning is the visual sign of spoilage for fruits and vegetables due to chemical reactions.
visual signs of spoilage for fruits and vegetables due to chemical reactions?
browning
the mixture of gases selected for a map package depends on the type of product, the packaging materials and the storage temperature. the atmosphere in an ma package consists mainly of adjusted amounts of n, o, and co reduction of o promotes delay in deteriorative reactions in foods such as lipid oxidation, browning reactions and growth of spoilage organisms. low o levels of 3-5% are used to slow down respiration rate in fruits and vegetables. in the case of red meat, however, high levels of o (∼80%) are used to reduce oxidation of myoglobin and maintain an attractive bright red color of the meat. meat color enhancement is not required for pork, poultry and cooked meats; therefore, a higher concentration of co is used to extend the shelf life. levels higher than 10% of co are phytotoxic for fruit and vegetables, so co is maintained below this level. n is mostly used as a filler gas to prevent pack collapse. in addition, it is also used to prevent oxidative rancidity in packaged products such as snack foods by displacing atmospheric air, especially oxygen, therefore extending shelf life. the use of noble gases such as helium (he), argon (ar) and xenon (xe) to replace n as the balancing gas in map can also be used to preserve and extend the shelf life of fresh and minimally processed fruits and vegetables. their beneficial effects are due to their higher solubility and diffusivity in water, making them more effective in displacing o from cellular sites and enzymatic o receptors.
modified atmosphere
freeze drying is a recent dehydration breakthrough-method that is restricted to high-value foods due to the high cost associated with the process. despite its cost, freeze-drying is very effective in retaining the overall quality and nutritional value of the food through a process called sublimation, where water is removed (evaporated) from food in its frozen state without the transition through the liquid state. removing water from food prevents spoilage as it does not give an environment that favors the growth of spoilage-causing microorganisms such as bacteria, mould, and yeast. freeze-drying also reduces the total weight of the food, especially fruit and vegetables that are mostly water, thus making the transportation of these products more efficient. vegetables used in instant soup mixes often undergo freeze-drying that helps them retain their nutritional value, texture, and flavor. furthermore, as the food remains rigid during dehydration, subliming water creates holes where the evaporated ice crystals used to be. this allows freeze-dried foods such as vegetables to retain their shape without shrinkage, and these foods rehydrate completely when water is added to the mix that fills the voids left by the subliming water. due to the reduced water content of the freeze-dried foods that inhibit the growth of microorganisms and prevents enzymatic chemical reactions, these foods are considered shelf-stable and can be kept safe from spoilage for years by preventing the reabsorption of moisture. freeze-dried foods can be stored in room temperature without the need for refrigeration.
instant soup