Effect of Osmo- and Convective Dehydrofreezing on Energy Efficiency and Some Physicochemical Properties of Frozen Red Pepper
Year 2022,
Volume: 20 Issue: 2, 103 - 113, 27.07.2022
Handan Başünal Gülmez
Ayhan Topuz
Abstract
The effect of osmotic and convective drying treatments on main physicochemical properties of frozen sliced red peppers was investigated. Sliced red peppers were dried partially using either osmotic dehydration or convective hot air drying before freezing in an air blast freezer at constant air velocity (2 m/s) and temperature (-25°C). The center temperature of osmo- and convective dehydrofrozen peppers reached -25°C in about 105 min, while it took 270 min for control samples. Frozen samples were stored at -18±2°C for 60 days, and the color, texture, ascorbic acid, enzyme activities, antioxidant activity (DPPH and ORAC) and total carotenoid content of samples were monitored during storage. Results showed that skin puncture values of samples decreased by storage time. The ascorbic acid content of sliced red pepper decreased by both treatments and storage time. The antioxidant activity values of control samples were higher than those of convective dehydrofrozen and osmo-dehydrofrozen samples. Both partial drying treatments reduced carotenoid loss significantly. The losses in total carotenoid contents were 58.0, 47.5 and 46.9% at the end of the storage period in control, osmo-dehydrofrozen and convective dehydrofrozen peppers, respectively. Significantly lower energy was used in osmotic dehydration compared to convective drying since no heating required for osmotic dehydration. Moreover, pre-drying of sliced red pepper required one-third of lower energy for freezing compared to direct freezing. This study showed that osmo-dehydrofreezing can be an economical method for sliced red peppers production.
Supporting Institution
The Scientific Research Projects Coordination Unit of Akdeniz University & The Scientific and Technological Research Council of Turkey (TUBITAK) (General Domestic PhD Scholarship Program) for support graduate education.
Project Number
FYL-2015-616
Thanks
The authors would like to thank The Scientific Research Projects Coordination Unit of Akdeniz University (Antalya, Turkey) for financial support (Project Number: FYL-2015-616). In addition, they would like to thank The Scientific and Technological Research Council of Turkey (TUBITAK) (General Domestic PhD Scholarship Program) for support graduate education.
References
- [1] Andrews, J. (1999). The Pepper Trail. The University of North Texas Press, Texas. 258 s.
- [2] Tregunno, N., Goff, H. (1996). Osmodehydrofreezing of apples: structural and textural effects. Food Research International, 29(5), 471-479.
- [3] Talens, P., Escriche, I., Martınez-Navarrete, N., Chiralt, A. (2003). Influence of osmotic dehydration and freezing on the volatile profile of kiwi fruit. Food Research International, 36(6), 635-642.
- [4] Chiralt, A., Martinez-Navarrete, N., Martinez-Monzó, J., Talens, P., Moraga, G., Ayala, A., Fito, P. (2001). Changes in mechanical properties throughout osmotic processes: Cryoprotectant effect. Journal of food Engineering, 49(2), 129-135.
- [5] Schudel, S., Prawiranto, K., Defraeye, T. (2021). Comparison of freezing and convective dehydrofreezing of vegetables for reducing cell damage. Journal of Food Engineering, 293, 110376.
- [6] Raoult-Wack, A., Lenart, A., Guilbert, S., Mujumdar, A. (1992). Recent advances in dewatering through immersion in concentrated solutions (‘Osmotic dehydration ‘), Elsevier Science Amsterdam,.
- [7] Eroglu, E., Yildiz, H. (2010). Recent developments in osmotic dehydration. Akademik Gıda, 8(6), 24-28.
- [8] Ponting, J., Watters, G., Forrey, R., Jackson, R., Stanley, W. (1966). Osmotic dehydration of fruits. Food Technology, 20(10), 125-128.
- [9] Lazarides, H.N., Mavroudis, N.E. (1996). Kinetics of osmotic dehydration of a highly shrinking vegetable tissue in a salt-free medium. Journal of food Engineering, 30(1), 61-74.
- [10] Rastogi, N., Eshtiaghi, M., Knorr, D. (1999). Accelerated mass transfer during osmotic dehydration of high intensity electrical field pulse pretreated carrots. Journal of food science, 64(6), 1020-1023.
- [11] Ade-Omowaye, B., Taiwo, K., Eshtiaghi, N., Angersbach, A., Knorr, D. (2003). Comparative evaluation of the effects of pulsed electric field and freezing on cell membrane permeabilisation and mass transfer during dehydration of red bell peppers. Innovative Food Science & Emerging Technologies, 4(2), 177-188.
- [12] Goula, A.M., Lazarides, H.N. (2012). Modeling of mass and heat transfer during combined processes of osmotic dehydration and freezing (osmo-dehydro-freezing). Chemical Engineering Science, 82, 52-61.
- [13] Torreggiani, D. (1995). Technological aspects of osmotic dehydration in foods. Technomic Publisher, Lanchester, PA, 281-304.
- [14] Robbers, M., Singh, R., Cunha, L.M. (1997). Osmotic‐convective dehydrofreezing process for drying kiwifruit. Journal of food science, 62(5), 1039-1042.
- [15] Conway, J., Castaigne, F., Picard, G., Vovan, X. (1983). Mass transfer considerations in the osmotic dehydration of apples. Canadian Institute of Food Science and Technology Journal, 16(1), 25-29.
- [16] Forni, E., Torreggiani, D., Crivelli, G., Maestrelli, A., Bertolo, G., Santelli, F. 1987. Influence of osmosis time on the quality of dehydrofrozen kiwi fruit. I International Symposium on Kiwifruit 282, pp. 425-434.
- [17] Huxsoll, C. (1982). Reducing the refrigeration load by partial concentration of foods prior to freezing. Food Technology, 5, 98-102.
- [18] Lazarides, H.N., Mavroudis, N.E. (1995). Freeze/thaw effects on mass transfer rates during osmotic dehydration. Journal of food science, 60(4), 826-828.
- [19] Giannakourou, M.C., Dermesonlouoglou, E.K., Taoukis, P.S. (2020). Osmodehydrofreezing: An integrated process for food preservation during frozen storage. Foods, 9(8), 1042.
- [20] Dermesonlouoglou, E., Zachariou, I., Andreou, V., Taoukis, P.S. (2018). Quality assessment and shelf life modeling of pulsed electric field pretreated osmodehydrofrozen kiwifruit slices. International Journal of Food Studies, 7(1).
- [21] Xin, Y., Zhang, M., Adhikari, B. (2014). Freezing characteristics and storage stability of broccoli (Brassica oleracea L. var. botrytis L.) under osmodehydrofreezing and ultrasound-assisted osmodehydrofreezing treatments. Food and bioprocess technology, 7(6), 1736-1744.
- [22] Topuz, A. (2008). A novel approach for color degradation kinetics of paprika as a function of water activity. LWT-food science and technology, 41(9), 1672-1677.
- [23] Vega-Gálvez, A., Di Scala, K., Rodríguez, K., Lemus-Mondaca, R., Miranda, M., López, J., Perez-Won, M. (2009). Effect of air-drying temperature on physico-chemical properties, antioxidant capacity, colour and total phenolic content of red pepper (Capsicum annuum, L. var. Hungarian). Food Chemistry, 117(4), 647-653.
- [24] Asami, D.K., Hong, Y.-J., Barrett, D.M., Mitchell, A.E. (2003). Comparison of the total phenolic and ascorbic acid content of freeze-dried and air-dried marionberry, strawberry, and corn grown using conventional, organic, and sustainable agricultural practices. Journal of Agricultural and Food Chemistry, 51(5), 1237-1241.
- [25] Žilić, S., Serpen, A., Akıllıoğlu, G., Janković, M., Gökmen, V. (2012). Distributions of phenolic compounds, yellow pigments and oxidative enzymes in wheat grains and their relation to antioxidant capacity of bran and debranned flour. Journal of cereal science, 56(3), 652-658.
- [26] Jarén-Galán, M., Mínguez-Mosquera, M.I. (1999). Effect of pepper lipoxygenase activity and its linked reactions on pigments of the pepper fruit. Journal of Agricultural and Food Chemistry, 47(11), 4532-4536.
- [27] Arslan, D., Özcan, M. (2011). Dehydration of red bell-pepper (Capsicum annuum L.): Change in drying behavior, colour and antioxidant content. Food and bioproducts processing, 89(4), 504-513.
- [28] Zhang, D., Hamauzu, Y. (2003). Phenolic compounds, ascorbic acid, carotenoids and antioxidant properties of green, red and yellow bell peppers. J. Food Agric. Environ, 1(2), 22-27.
- [29] Fernández-León, M., Fernández-León, A., Lozano, M., Ayuso, M., González-Gómez, D. (2013). Altered commercial controlled atmosphere storage conditions for ‘Parhenon’broccoli plants (Brassica oleracea L. var. italica). Influence on the outer quality parameters and on the health-promoting compounds. LWT-food science and technology, 50(2), 665-672.
- [30] Ena, A., Pintucci, C., Carlozzi, P. (2012). The recovery of polyphenols from olive mill waste using two adsorbing vegetable matrices. Journal of biotechnology, 157(4), 573-577.
- [31] Chuah, A.M., Lee, Y.-C., Yamaguchi, T., Takamura, H., Yin, L.-J., Matoba, T. (2008). Effect of cooking on the antioxidant properties of coloured peppers. Food Chemistry, 111(1), 20-28.
- [32] Motevali, A., Minaei, S., Khoshtagaza, M.H. (2011). Evaluation of energy consumption in different drying methods. Energy conversion and management, 52(2), 1192-1199.
- [33] Kuljanin, T., Mišljenović, N., Koprivica, G., Lević, L., Jevrić, L., Pejić, D. (2011). Energy and material balance of the osmotic dehydration with evaporation and osmotic solution recirculation. Journal on Processing and Energy in Agriculture, 15(4), 235-238.
- [34] Sahin, S., Sumnu, S.G. (2006). Thermal properties of foods, Springer, New York
- [35] Siebel, J. (1892). Specific heat of various products. Ice & Refrig., 2, 256.
- [36] Tumer, E., Tulek, Y. (2021). Effects of dehydrofreezing conditions on carrot β-carotene and kinetics of β-carotene change in dehydrofrozen carrots during storage. Food Science and Technology, 42, https://doi.org/10.1590/fst.70220
- [37] Ade-Omowaye, B., Rastogi, N., Angersbach, A., Knorr, D. (2002). Osmotic dehydration of bell peppers: influence of high intensity electric field pulses and elevated temperature treatment. Journal of food Engineering, 54(1), 35-43.
- [38] Vial, C., Guilbert, S., Cuq, J. (1991). Osmotic dehydration of kiwi fruits: influence of process variables on the color and ascorbic acid content. Sciences des aliments, 11(1), 63-84.
- [39] Kim, B.-Y., Lee, K.-H. (2009). Effect of freezing on the physicochemical properties of semi-dried red pepper. Korean Journal of Food Preservation, 16(3), 362-370.
- [40] Ramallo, L., Mascheroni, R. (2010). Dehydrofreezing of pineapple. Journal of Food Engineering, 99(3), 269-275.
- [41] Inyang, U., Ike, C. (1998). Effect of blanching, dehydration method and temperature on the ascorbic acid, colour, sliminess and other constituents of okra fruit. International journal of food sciences and nutrition, 49(2), 125-130.
- [42] Lemus-Mondaca, R., Miranda, M., Grau, A.A., Briones, V., Villalobos, R., Vega-Gálvez, A. (2009). Effect of osmotic pretreatment on hot air drying kinetics and quality of Chilean papaya (Carica pubescens). Drying Technology, 27(10), 1105-1115.
- [43] Piga, A., Pinna, I., Özer, K.B., Agabbio, M., Aksoy, U. (2004). Hot air dehydration of figs (Ficus carica L.): drying kinetics and quality loss. International journal of food science & technology, 39(7), 793-799.
- [44] Vega-Gálvez, A., Lemus-Mondaca, R., Bilbao-Sáinz, C., Fito, P., Andrés, A. (2008). Effect of air drying temperature on the quality of rehydrated dried red bell pepper (var. Lamuyo). Journal of food Engineering, 85(1): 42-50.
- [45] Martínez, S., López, M., González-Raurich, M., Bernardo Alvarez, A. (2005). The effects of ripening stage and processing systems on vitamin C content in sweet peppers (Capsicum annuum L.). International journal of food sciences and nutrition, 56(1), 45-51.
- [46] Oruna-Concha, M., Gonzalez-Castro, M., Lopez-Hernandez, J., Simal-Lozano, J. (1998). Monitoring of the vitamin C content of frozen green beans and Padrón peppers by HPLC. Journal of the Science of Food and Agriculture, 76(3):,477-480.
- [47] Bahçeci, K.S., Serpen, A., Gökmen, V., Acar, J. (2005). Study of lipoxygenase and peroxidase as indicator enzymes in green beans: change of enzyme activity, ascorbic acid and chlorophylls during frozen storage. Journal of food Engineering, 66(2), 187-192.
- [48] Kanner, J., Mendel, H., Budowski, P. (1977). Carotene oxidizing factors in red pepper fruits (Capsicum annuum L.): peroxidase activity. Journal of food science, 42(6), 1549-1551.
Osmotik ve Konvektif Kurutma Sonrası Dondurma İşleminin Enerji Verimliliğine ve Kırmızıbiberin Bazı Fizikokimyasal Özellikleri Üzerine Etkisi
Year 2022,
Volume: 20 Issue: 2, 103 - 113, 27.07.2022
Handan Başünal Gülmez
Ayhan Topuz
Abstract
Ozmotik ve konvektif kurutma işlemlerinin kısmen kurutularak dondurulmuş kırmızıbiber dilimlerinin başlıca fizikokimyasal özelliklerine etkisi araştırılmıştır. Dilimlenmiş kırmızıbiberler, ozmotik dehidrasyon veya konvektif sıcak havayla kurutma sonrasında sabit hava hızında (2 m/s) ve sıcaklıkta (-25°C) bir dondurucuda dondurulmuştur. Dondurma işleminde kısmen kurutularak dondurulmuş biberlerin merkez sıcaklığı yaklaşık 105 dakikada -25°C'ye ulaşırken, kontrol örnekleri bu sıcaklığa 270 dakikada ulaşmıştır. Dondurulmuş örnekler 60 gün süreyle -18±2°C'de depolanmış olup, bu süreçte örneklerin renk, yapı, askorbik asit, enzim aktiviteleri, antioksidan aktivite (DPPH ve ORAC) ve toplam karotenoid içeriği takip edilmiştir. Yapı analiz sonuçları örneklerin kabuk delinme değerlerinin depolama süresi ile azaldığını göstermiştir. Dilimlenmiş kırmızıbiberin askorbik asit içeriği hem uygulamalar ile hem de depolama süresi ile azalmıştır. Kontrol örneklerinin antioksidan aktivite değerleri, osmo- ve konvektif kurutma ile kısmen kurutulduktan sonra dondurulmuş örneklerden daha yüksek bulunmuştur. Her iki kısmi kurutma işlemi de karotenoid kaybını önemli ölçüde azaltmıştır. Kontrol örneği ile osmo- ve konvektif kurutma işlemleriyle kısmen kurutulduktan sonra dondurulmuş kırmızıbiberlerde depolama süresinin sonunda toplam karotenoid kayıpları sırasıyla %58.0, 47.5 ve 46.9 olarak tespit edilmiştir. Ozmotik dehidrasyon işleminde ısıtma gerekmediğinden, konvektif kurutmaya kıyasla daha düşük enerji girdisi hesaplanmıştır. Ayrıca dilimlenmiş kırmızıbiberin kısmi kurutma sonrası dondurma işleminde, doğrudan dondurmaya kıyasla üçte bir oranında daha düşük enerji kullanılmıştır. Bu çalışma, dilimlenmiş kırmızıbiber üretiminde ozmotik dehidrasyonla kısmi kurutma sonrası dondurma işleminin ekonomik bir yöntem olabileceğini göstermiştir.
Project Number
FYL-2015-616
References
- [1] Andrews, J. (1999). The Pepper Trail. The University of North Texas Press, Texas. 258 s.
- [2] Tregunno, N., Goff, H. (1996). Osmodehydrofreezing of apples: structural and textural effects. Food Research International, 29(5), 471-479.
- [3] Talens, P., Escriche, I., Martınez-Navarrete, N., Chiralt, A. (2003). Influence of osmotic dehydration and freezing on the volatile profile of kiwi fruit. Food Research International, 36(6), 635-642.
- [4] Chiralt, A., Martinez-Navarrete, N., Martinez-Monzó, J., Talens, P., Moraga, G., Ayala, A., Fito, P. (2001). Changes in mechanical properties throughout osmotic processes: Cryoprotectant effect. Journal of food Engineering, 49(2), 129-135.
- [5] Schudel, S., Prawiranto, K., Defraeye, T. (2021). Comparison of freezing and convective dehydrofreezing of vegetables for reducing cell damage. Journal of Food Engineering, 293, 110376.
- [6] Raoult-Wack, A., Lenart, A., Guilbert, S., Mujumdar, A. (1992). Recent advances in dewatering through immersion in concentrated solutions (‘Osmotic dehydration ‘), Elsevier Science Amsterdam,.
- [7] Eroglu, E., Yildiz, H. (2010). Recent developments in osmotic dehydration. Akademik Gıda, 8(6), 24-28.
- [8] Ponting, J., Watters, G., Forrey, R., Jackson, R., Stanley, W. (1966). Osmotic dehydration of fruits. Food Technology, 20(10), 125-128.
- [9] Lazarides, H.N., Mavroudis, N.E. (1996). Kinetics of osmotic dehydration of a highly shrinking vegetable tissue in a salt-free medium. Journal of food Engineering, 30(1), 61-74.
- [10] Rastogi, N., Eshtiaghi, M., Knorr, D. (1999). Accelerated mass transfer during osmotic dehydration of high intensity electrical field pulse pretreated carrots. Journal of food science, 64(6), 1020-1023.
- [11] Ade-Omowaye, B., Taiwo, K., Eshtiaghi, N., Angersbach, A., Knorr, D. (2003). Comparative evaluation of the effects of pulsed electric field and freezing on cell membrane permeabilisation and mass transfer during dehydration of red bell peppers. Innovative Food Science & Emerging Technologies, 4(2), 177-188.
- [12] Goula, A.M., Lazarides, H.N. (2012). Modeling of mass and heat transfer during combined processes of osmotic dehydration and freezing (osmo-dehydro-freezing). Chemical Engineering Science, 82, 52-61.
- [13] Torreggiani, D. (1995). Technological aspects of osmotic dehydration in foods. Technomic Publisher, Lanchester, PA, 281-304.
- [14] Robbers, M., Singh, R., Cunha, L.M. (1997). Osmotic‐convective dehydrofreezing process for drying kiwifruit. Journal of food science, 62(5), 1039-1042.
- [15] Conway, J., Castaigne, F., Picard, G., Vovan, X. (1983). Mass transfer considerations in the osmotic dehydration of apples. Canadian Institute of Food Science and Technology Journal, 16(1), 25-29.
- [16] Forni, E., Torreggiani, D., Crivelli, G., Maestrelli, A., Bertolo, G., Santelli, F. 1987. Influence of osmosis time on the quality of dehydrofrozen kiwi fruit. I International Symposium on Kiwifruit 282, pp. 425-434.
- [17] Huxsoll, C. (1982). Reducing the refrigeration load by partial concentration of foods prior to freezing. Food Technology, 5, 98-102.
- [18] Lazarides, H.N., Mavroudis, N.E. (1995). Freeze/thaw effects on mass transfer rates during osmotic dehydration. Journal of food science, 60(4), 826-828.
- [19] Giannakourou, M.C., Dermesonlouoglou, E.K., Taoukis, P.S. (2020). Osmodehydrofreezing: An integrated process for food preservation during frozen storage. Foods, 9(8), 1042.
- [20] Dermesonlouoglou, E., Zachariou, I., Andreou, V., Taoukis, P.S. (2018). Quality assessment and shelf life modeling of pulsed electric field pretreated osmodehydrofrozen kiwifruit slices. International Journal of Food Studies, 7(1).
- [21] Xin, Y., Zhang, M., Adhikari, B. (2014). Freezing characteristics and storage stability of broccoli (Brassica oleracea L. var. botrytis L.) under osmodehydrofreezing and ultrasound-assisted osmodehydrofreezing treatments. Food and bioprocess technology, 7(6), 1736-1744.
- [22] Topuz, A. (2008). A novel approach for color degradation kinetics of paprika as a function of water activity. LWT-food science and technology, 41(9), 1672-1677.
- [23] Vega-Gálvez, A., Di Scala, K., Rodríguez, K., Lemus-Mondaca, R., Miranda, M., López, J., Perez-Won, M. (2009). Effect of air-drying temperature on physico-chemical properties, antioxidant capacity, colour and total phenolic content of red pepper (Capsicum annuum, L. var. Hungarian). Food Chemistry, 117(4), 647-653.
- [24] Asami, D.K., Hong, Y.-J., Barrett, D.M., Mitchell, A.E. (2003). Comparison of the total phenolic and ascorbic acid content of freeze-dried and air-dried marionberry, strawberry, and corn grown using conventional, organic, and sustainable agricultural practices. Journal of Agricultural and Food Chemistry, 51(5), 1237-1241.
- [25] Žilić, S., Serpen, A., Akıllıoğlu, G., Janković, M., Gökmen, V. (2012). Distributions of phenolic compounds, yellow pigments and oxidative enzymes in wheat grains and their relation to antioxidant capacity of bran and debranned flour. Journal of cereal science, 56(3), 652-658.
- [26] Jarén-Galán, M., Mínguez-Mosquera, M.I. (1999). Effect of pepper lipoxygenase activity and its linked reactions on pigments of the pepper fruit. Journal of Agricultural and Food Chemistry, 47(11), 4532-4536.
- [27] Arslan, D., Özcan, M. (2011). Dehydration of red bell-pepper (Capsicum annuum L.): Change in drying behavior, colour and antioxidant content. Food and bioproducts processing, 89(4), 504-513.
- [28] Zhang, D., Hamauzu, Y. (2003). Phenolic compounds, ascorbic acid, carotenoids and antioxidant properties of green, red and yellow bell peppers. J. Food Agric. Environ, 1(2), 22-27.
- [29] Fernández-León, M., Fernández-León, A., Lozano, M., Ayuso, M., González-Gómez, D. (2013). Altered commercial controlled atmosphere storage conditions for ‘Parhenon’broccoli plants (Brassica oleracea L. var. italica). Influence on the outer quality parameters and on the health-promoting compounds. LWT-food science and technology, 50(2), 665-672.
- [30] Ena, A., Pintucci, C., Carlozzi, P. (2012). The recovery of polyphenols from olive mill waste using two adsorbing vegetable matrices. Journal of biotechnology, 157(4), 573-577.
- [31] Chuah, A.M., Lee, Y.-C., Yamaguchi, T., Takamura, H., Yin, L.-J., Matoba, T. (2008). Effect of cooking on the antioxidant properties of coloured peppers. Food Chemistry, 111(1), 20-28.
- [32] Motevali, A., Minaei, S., Khoshtagaza, M.H. (2011). Evaluation of energy consumption in different drying methods. Energy conversion and management, 52(2), 1192-1199.
- [33] Kuljanin, T., Mišljenović, N., Koprivica, G., Lević, L., Jevrić, L., Pejić, D. (2011). Energy and material balance of the osmotic dehydration with evaporation and osmotic solution recirculation. Journal on Processing and Energy in Agriculture, 15(4), 235-238.
- [34] Sahin, S., Sumnu, S.G. (2006). Thermal properties of foods, Springer, New York
- [35] Siebel, J. (1892). Specific heat of various products. Ice & Refrig., 2, 256.
- [36] Tumer, E., Tulek, Y. (2021). Effects of dehydrofreezing conditions on carrot β-carotene and kinetics of β-carotene change in dehydrofrozen carrots during storage. Food Science and Technology, 42, https://doi.org/10.1590/fst.70220
- [37] Ade-Omowaye, B., Rastogi, N., Angersbach, A., Knorr, D. (2002). Osmotic dehydration of bell peppers: influence of high intensity electric field pulses and elevated temperature treatment. Journal of food Engineering, 54(1), 35-43.
- [38] Vial, C., Guilbert, S., Cuq, J. (1991). Osmotic dehydration of kiwi fruits: influence of process variables on the color and ascorbic acid content. Sciences des aliments, 11(1), 63-84.
- [39] Kim, B.-Y., Lee, K.-H. (2009). Effect of freezing on the physicochemical properties of semi-dried red pepper. Korean Journal of Food Preservation, 16(3), 362-370.
- [40] Ramallo, L., Mascheroni, R. (2010). Dehydrofreezing of pineapple. Journal of Food Engineering, 99(3), 269-275.
- [41] Inyang, U., Ike, C. (1998). Effect of blanching, dehydration method and temperature on the ascorbic acid, colour, sliminess and other constituents of okra fruit. International journal of food sciences and nutrition, 49(2), 125-130.
- [42] Lemus-Mondaca, R., Miranda, M., Grau, A.A., Briones, V., Villalobos, R., Vega-Gálvez, A. (2009). Effect of osmotic pretreatment on hot air drying kinetics and quality of Chilean papaya (Carica pubescens). Drying Technology, 27(10), 1105-1115.
- [43] Piga, A., Pinna, I., Özer, K.B., Agabbio, M., Aksoy, U. (2004). Hot air dehydration of figs (Ficus carica L.): drying kinetics and quality loss. International journal of food science & technology, 39(7), 793-799.
- [44] Vega-Gálvez, A., Lemus-Mondaca, R., Bilbao-Sáinz, C., Fito, P., Andrés, A. (2008). Effect of air drying temperature on the quality of rehydrated dried red bell pepper (var. Lamuyo). Journal of food Engineering, 85(1): 42-50.
- [45] Martínez, S., López, M., González-Raurich, M., Bernardo Alvarez, A. (2005). The effects of ripening stage and processing systems on vitamin C content in sweet peppers (Capsicum annuum L.). International journal of food sciences and nutrition, 56(1), 45-51.
- [46] Oruna-Concha, M., Gonzalez-Castro, M., Lopez-Hernandez, J., Simal-Lozano, J. (1998). Monitoring of the vitamin C content of frozen green beans and Padrón peppers by HPLC. Journal of the Science of Food and Agriculture, 76(3):,477-480.
- [47] Bahçeci, K.S., Serpen, A., Gökmen, V., Acar, J. (2005). Study of lipoxygenase and peroxidase as indicator enzymes in green beans: change of enzyme activity, ascorbic acid and chlorophylls during frozen storage. Journal of food Engineering, 66(2), 187-192.
- [48] Kanner, J., Mendel, H., Budowski, P. (1977). Carotene oxidizing factors in red pepper fruits (Capsicum annuum L.): peroxidase activity. Journal of food science, 42(6), 1549-1551.