Freezing is the process of ice crystallization from supercooled water. Ice crystal morphology plays an important role in the textural and physical properties of frozen and frozen-thawed foods and in processes such as freeze drying, freeze concentration, and freeze texturization. Size and location of ice crystals are key in the quality of thawed tissue products. In ice cream, smaller ice crystals are preferred because large crystals results in an icy texture. In freeze drying, ice morphology influences the rate of sublimation and several morphological characteristics of the freeze-dried matrix as well as the biological activity of components (e.g., in pharmaceuticals). In freeze concentration, ice morphology influences the efficiency of separation of ice crystals from the concentrated solution. The cooling rate has been the most common variable controlling ice morphology in frozen and partly frozen systems. However, several new approaches show promise in controlling nucleation (consequently, ice morphology), among them are the use of ice nucleation agents, antifreeze proteins, ultrasound, and high pressure. This paper summarizes the fundamentals of freezing, methods of observation and measurement of ice morphology, and the role of ice morphology in technological applications.

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The effect of osmotic dehydration (OD) at atmospheric pressure and vacuum impregnation (VI) treatments on some physiochemical parameters of papaya (a w , pH, color, firmness, and microstructure) was analyzed. Osmotic treatments were carried out on papaya with 55°Brix and 65°Brix sucrose solutions at 30°C. VI with 65°Brix osmotic solution was the most effective in reducing a w due to the highest sucrose gain during osmotic treatment. Color differences were associated to loss of clarity in line with transparency gain. Scanning electron microscopy observations show that osmotic dehydration caused shape changes and size reduction of papaya cells; also differences in microstructural features were observed between OD-treated and VI-treated samples. Moreover, the largest firmness observed in VI samples compared with OD treatments was associated with the thickness of the middle lamella between cells, which was greater in VI than OD treatments. Improvement in texture and palatability of papaya was obtained with VI rather than OD treatment compared with fresh papaya.

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This study aimed to evaluate the potential of centrifugal block cryoconcentration (CBCC) at three cycles applied to fresh calafate juice. The fresh juice and cryoconcentrate at each cycle were stored for five weeks at 4 °C and quality attributes were analyzed every 7 days. CBCC had significant effects in the calafate juice, since in the last cycle, the cryoconcentrate reached a high value of total soluble solids (TSS, ≈42 °Brix), with final attractive color, and an increase of approximately 2.5, 5.2, 5.1, 4.0 and 5.3 times in relation to the fresh juice values, for total bioactive compounds (TBC), 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), ferric reducing antioxidant power (FRAP) and oxygen radical absorbance capacity (ORAC), respectively. However, at 35 days under storage, these values decreased by 5%, 13%, 15%, 19%, 24% and 27%, for TSS, TBC, DPPH, ABTS, FRAP and ORAC, respectively. Additionally, until the day 14, the panelists indicated a good acceptability of the reconstituted cryoconcentrate. Therefore, CBCC can be considered a novel and viable technology for the preservation of quality attributes from fresh calafate juice with interesting food applications of the cryoconcentrates due to their high stability during storage time in comparison to the fresh juice.