Evaluation of freezing pre-treatments for the lyophilisation of apple

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Abstract

The effect of freezing rate on the quality of dried Jonagold and Idared (Malus domestica Borkh.) was studied. Apple slices underwent various pre-treatments, i.e. freezing in household freezer (freezing speed/rate: 0,5◦C/min), contact plate freezing (2◦C/min) and vacuumfreezing (3◦C/min). The quality of the freeze-dried product was then evaluated in terms of water activity (aw), hardness, color and rehydration. The texture and color experiments were carried out with texture analyser and colorimeter. The aw of apple slices was measured by aw apparatus. It was found that drying time was influenced by freezing rate. The freezing in household freezer (slow freezing rate) significantly reduces the duration of the freeze-drying process and consequently the process costs. The slow freezing rate allows the growth of large ice crystals at the beginning of the freeze-drying process; this fact should consequently lead to larger pores and injured cell walls and thus to shorter freeze-drying time. Quality of the freezing in household freezer product was assessed as higher than the quality of the other freezing pre-treated material. Slow freezing rate resulted softer texture and higher rehydration capacity than that of other pre-treated samples. In all cases, slow freezing speed lead to lower final moisture content, total color difference and water activity. Freeze-dried samples prepared with higher freezing rates (3◦C/min) were the most white in color because small pores, originated by sublimation of small ice crystals formed by fast freezing.

[1] Antal, T.: A fagyaszt´as, mint el˝okezel´es hat´asa a szublim´aci´os sz´ar´ıt´as m˝uk¨od´esi idej´ere ´es a v´egterm´ek min˝os´eg´ere. ´Elelmiszer Tudom´any Technol ´ogia, 67 (2013/4).

[2] Araki, T., Sagara, Y., Abdullah, K., Tambunan, A. H.: Transport properties of cellular food materials undergoing freeze-drying. Drying Technology, 19 (2001), 297-312.

[3] Beaudry, C., Raghavan, G. S. V., Ratti, C., Rennie, T. J.: Effect of four drying methods on the quality of osmotically dehydrated cranberries. Drying Technology, 22 (2004/3), 521-539.

[4] Ceballos, A. M., Giraldo, G. I., Orrego, C. E.: Effect of freezing rate on quality parameters of freeze dried soursop fruit pulp. Journal of Food Engineering, 111 (2012), 360-365.

[5] Doymaz, I.: An experimental study on drying of green apples. Drying Technology, 27 (2009), 478-485.

[6] Doymaz, I.: Effect of citric acid and blanching pre-treatments on drying and rehydration of Amasya red apples. Food and Bioproducts Processing, 88 (2010), 124-132.

[7] Eshtiaghi, M. N., Stute, R., Knorr, D.: High-pressure and freezing pretreatment effects on drying, rehydration, texture and color of green beans, carrots and potatoes. Journal of Food Science, 59 (1994), 1168-1170.

[8] Feng, H., Tang, J.: Microwave finish drying of diced apples in a spouted bed. Journal of Food Science, 63 (1998), 679-683.

[9] Ghio, S., Barresi, A. A., Rovero, G.: A comparison of evaporate and conventional freezing prior to freeze-drying of fruits and vegetables. Institution of Chemical Engineering, 78 (2000), 187-192.

[10] Jackel, T., Dautel, K., Ternes, W.: Preserving functional properties of hen’s egg yolk during freeze-drying. Journal of Food Engineering, 87 (2008), 522-526.

[11] McLaughlin, C. P., Magee, T. R. A.: The determination of sorption isotherm and isosteric heats of sorption for potatoes. Journal of Food Engineering, 35 (1998), 267-280.

[12] Nail, S., Gatlin, L.: Freeze drying: Principle and practice. In Avis, A. - Liebermann, A. - Lachann, I. (Ed.): Pharmaceutical dosage forms, Vol. 2. Marcel Dekker Inc., New York, 1993, 163-333.

[13] Pikal, M. J.: Freeze drying. In Swarbick, J. (Ed.): Encyclopedia of Pharmaceutical Technology. Informa Healthcare, New York, 2007, 1807-1832.

[14] Reyes, A., Bubnovich, V., Bustos, R., V´asquez, M., Vega, R., Scheuermann, E.: Comparative study of different process conditions of freeze drying of ’Murtilla’ berry. Drying Technology, 28 (2010), 1416-1425.

[15] Rovero, G., Ghio, S., Barresi, A. A.: Development of a prototype capacitive balance for freeze-drying studies. Chemical Engineering Science, 56 (2001/11), 3575-3584.

[16] Tregunno, N. B., Goff, H. D.: Osmodehydrofreezing of apples: Structural and textural effects. Food Research International, 29 (1996), 471-479.

[17] Wang, Y., Zhang, M., Mujumdar, A. S., Mothibe, K. J.: Experimental investigation and mechanism analysis on microwave freeze drying of stem lettuce cubes in a circular conduit. Drying Technology, 30 (2012), 1377-1386.

Acta Universitatis Sapientiae, Agriculture and Environment

The Journal of "Sapientia" Hungarian University of Transylvania

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