Carrots freeze-drying

Preparation of the alcohol insoluble solids (AIS) The content of the can was drained and the carrot cubes were immediately frozen in hquid nitrogen, freeze-dried and milled. Carrot powder (ca. 10 g) was mixed with 200 ml 80% ethanol previously heated to 60°C. After filtration the residue was extracted with ethanol until the filtrate was colorless (5 times) and gave negative reaction with phenol-sulfuric acid test (Dubois et al., 1956). 

Lutein Freeze-dried carrot pulp powder (25°C) 5.4x10 Tang and Chen (2000)... 

Particle size. For the extraction of carotenoids from freeze-dried carrot using SC-CO2, the studies of Goto and others (1994) and Sun and Temelli (2006) show that a higher extraction yield was obtained with small carrot particles. In the study of Sun and Temelli (2006), the total carotenoid yield increased from 1,110 to 1,370 and 1,504 pg/g dry carrot with particle sizes of 1-2 mm to 0.5-1 mm and 0.3-0.5 mm, respectively. 

Flow rate and extraction time. Dynamic techniques for the extraction of carotenoids with SC-CO2 use flow rates that vary from 0.5 to 15 mL/min (measured at extraction temperature and pressure) with different effects depending on the matrix (Rozzi and others 2002 Subra and others 1998 Saldana and others 2006). Subra and others (1998) extracted (3-carotene from 1 to 2.5 g freeze-dried carrots and studied the effect of flow rates (0.4 and 1.2 liter/min) they obtained higher yields of (3-carotene at a flow rate of 1.2 liter/min. Sun and Temelli (2006) also evaluated the effect of flow rate (0.5 and 1.0 liter/min) on the extraction of (3-carotene with SC-CO2 + canola oil. The total carotenoids yield increased with flow rate, ranging from 934.8 to 1,973.6 pg/g dry carrot at C02 flow rates from 0.5 to 2 liter/min (measured at STP), respectively (Sun and Temelli, 2006). However, the lycopene yield decreased from 38.8% to 8% as flow rate was increased from 2.5 to 15 mL/min (measured at extraction temperature and pressure) (Rozzi and others 2002). 

For the constant-temperature heating experiments different product water contents were obtained by storage of freeze-dried carrots over saturated salt solutions (17). 

The influence of the carrot variety on Maillard reaction Samples of six freeze-dried carrot varieties were equilibrated at room temperature to a water activity of 0.33 (J 7), corresponding to an average water content of 6.3 % (related to wet matter). Then the samples were heated to 55 °C for 30 h and the concentrations of Amadori compounds as well as the corresponding sensory changes were determined. The results are listed in Table IV. The amount of Amadori compounds formed by the heating process seems to be correlated... 

The storage of freeze-dried carrots for 24 months in sealed cans under air and N2 and in glass containers under vacuum at room temperature was studied by Gegow [4.29]. Fifteen quality parameters were evaluated and found to be comparable to those of frozen carrots. The carotenes were only reasonably preserved under vacuum. 

As and DMA were found to be the main species in rice-based and mixed rice/formula cereals, although traces of MM A were also detected. Inorganic As was present in freeze-dried sweet potatoes, carrots, green beans, and peaches. MM A and DMA were not detected in these samples [29]. 

The methanol-to-water ratio in the extraction mixture is usually determined on the basis of the water content of the sample. Methanol alone is generally used if fresh, untreated samples are dealt with, because the natural water content (reaching even 90 percent m/m) in practice adds to methanol [109, 110] however, in some studies, nonaqueous methanol has used been also for freeze-dried samples [26, 111, 112]. The methanol-to-water ratio mostly chosen is around 1 1 v/v (40 60, 50 50, 60 40). However, also the 10 90 ratio is also used [100], not to mention cases where the full mixture scale from 0 to 100 percent methanol has been exploited [113, 114]. The study by Helgesen and Larsen [115], where a 10 percent (v/v) methanol mixture was used for the extraction of As species from carrots because of its antibacterial effect, is noteworthy. 

Extraction of Polysaccharides from Carrot OHM. CWM (25 g) was extracted three times by stirring in water (1 L) for 2 h at 80°. After each extraction Che suspension was centrifuged and Che combined supernatant liquids were freeze-dried Co give polysaccharide fraction A (0.5 g). 

Reyes, A., Vega, R.V., and Bruna, R.D., Effect of operating conditions in atmospheric freeze drying of carrot particles in a pulsed fluidized bed. Drying TechnoL, 28,1185-1192,2010. 

Fat-soluble vitamins are expected to degrade by the oxidation mechanism. The degradation is superimposed by direct thermal reactions during drying of the food products. This is evidenced by comparing air drying and freeze drying of carrots (Table 24.8). 

Atmospheric freeze-drying of several foods, including mushrooms and carrots, was investigated in a fluidized bed of finely divided adsorbent that combined adsorption and fluidization, achieving improved heat and mass transfer and shorter drying time than vacuum drying [50,51]. Products could be dried economically using very simple equipment. 

The study of the rehydration ratios of forced air-dried compressed carrots after partially freeze-drying to different moisture levels showed the drying treatment significantly affected rehydration ratios in all cases [66]. The sample that was freeze-dried to 50% moisture, compressed, and then air-dried had the highest ratio and was the quickest to rehydrate. In comparison, the totally freeze-dried and hot air-dried compressed carrots showed much lower values of rehydration ratios. These observations were supported by scanning electron microscopy (SEM), which showed collapse of cellular structure and tissue coagulation to act as a barrier for rehydration. 

Carotenoids in freeze-dried carrots were relatively more stable in the range of 0.32-0.57a [71]. The maximum stability was near 0.43a (corresponding to an equilibrium moisture content of 8.8%-10%). Increase in the rate of carotenoid destruction was greater at lower than at higher... 

E.R. Shadle, E.E. Bums, and L.J. Talley, Forced air drying of partially freeze dried compressed carrot bars, J. Food Sci., 48(1) 193 (1983). 

Lin TM, Durance TD, Seaman CH. Characterization of vacuum microwave, air and freeze dried carrot slices. Food Research International 31(2) 111-117, 1998. 

Tajiri, T., Matsumoto, K. and Hara, K. (1976). Storage stability of freeze-dried carrots. III. The content of carotene as affected by the addition of cysteine hydrochloride at various temperatures. J. Japan. Soc. Hort. Sci.. 45, 81-88. 

---