Effect of different cooking methods on structure and quality of industrially frozen carrots

Abstract

The effect of boiling, steaming and microwaving on microstructure, texture and colour of raw and industrially frozen carrots was investigated. The raw carrots, after cooking, showed dehydrated and separated cells with swollen walls. The carrots subjected to blanching, freezing and followed by frozen storage exhibited marked tissue damages indicating deep oriented fissures. Cooking caused cellular dehydration and separation in the tissue, with the same intensity between raw and frozen carrots and independently from the cooking treatment applied. Among different cooking methods, microwaving showed better retention of the initial texture and colour quality for both raw and frozen carrots. On the other hand, the steamed carrots revealed the highest degree of softening and colour differences from the control for both raw and frozen carrots, despite the worst tissue conditions were observed for the boiled carrots.

Application and optimisation of air–steam cooking on selected vegetables: impact on physical and antioxidant properties

“…The reduction of b *, in comparison to the raw sample, was more visible for the longer cooking times. The decrease of L * indicates darkening, while the reduction of both a* and b * indicates a general colour loss, as already reported for cooked carrots . These observations may be related to a decrease and/or isomerisation of α ‐ and β ‐carotene, the orange pigments of which the pumpkin is rich, as previously reported by other authors …”

“…The cutting test revealed a significant decrease of the shearing force (F s ) in comparison to the raw samples for both vegetables under all the cooking conditions. The obtained results may be related to the tissue damages caused by heating, as already reported by several authors 5,7 who observed the softening of vegetables when subjected to different cooking techniques. Such damages were described as cell plasmolysis and cell separation and have been attributed to the breakage of chemical bonds between the pectic components of middle lamellae, and the hydrolysis of some other components of the cell wall (i.e.…”

“…When the same vegetables were vacuum‐packaged (sous‐vide), a further improved retention of phytochemicals and antioxidant properties was showed. Other authors found a better texture retention in microwave cooked carrot discs in comparison to the boiled and steamed samples, with boiling the cooking practice that mostly affected the microstructure. On the other hand, other authors found that steaming was the method that less affected the polyphenol concentration and the antioxidant capacity of a wide range of vegetables, whereas microwaving was the worst method.…”

“…In most cases, cooking is used as an indispensable prerequisite to obtaining more digestible, safe and convenience food products. Moreover, cooking can profoundly affect the organoleptic and nutritional value of vegetables …”

“…Moreover, cooking can profoundly affect the organoleptic and nutritional value of vegetables. 4,5 The effect of different cooking techniques on organoleptic and nutritional (evaluated in terms of phytochemicals) quality of fresh vegetables has been investigated in several recent studies. [6][7][8] However, contrasting results have been reported due to the process conditions and the type of samples.…”