M. Nourmohamadpor Omran 1, M. Kh. Pirouzifard 1, P. Aryaey 2, and M. Hasan Nejad 3 ABSTRACT INTRODUCTION

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1 J. Agr. Sci. Tech. (213) Vol. 15: centration of Sour Cherry an Orange Juices with Novel Clarification Metho; Comparison of Concentration with Freeze Concentration in liqui Foos M. Nourmohamapor Omran 1, M. Kh. Pirouzifar 1, P. Aryaey 2, an M. Hasan Neja 3 ABSTRACT Sour cherry an orange juice were successfully cryoconcentrate. Novel clarification (Electro-Flotation an Ultra-Filtration) improve cryconcentration efficiency. EF-UF clarifie sour cherry an orange juices were cryoconcentrate in three stages up to 34.52±.14, 44.42±.19, 52.44±.13 an 28.43±.16, 4.51±.15, an 45.42±.19 Brix at - 1 C respectively. Duncan ' s multiple range test was use to compare mean values of various parameters. At similar total soluble soli, cryoconcentrate samples showe significantly (P<.5) higher retention of aroma number, ascorbic aci, an TAA compare to those thermally concentrate. concentration inuce formation of hyroxymethylfurfural more than cryoconcentration process use for concentration of orange juice. Keywors : Aroma number, Ascorbic aci, Electro-flotation, Hyroxylmethylfurfural, Total antioxiant activity. INTRODUCTION Prouction of fruit juice concentrate is base on ifferent technologies that inclue thermal concentration, membrane concentration, an cryoconcentration. Fruit juices are important sources of nutrients an energy, an play an important part in human nutrition. Also, it has been observe that consumption of fruit juices can prevent certain iseases such as cancer an cario-vascular iseases as fruit juices are rich in antioxiant vitamins incluing vitamin C an E, phenolic compouns, an carotene (Block et al., 21; Burns et al., 23; Garner et al., 2; John et al., 22; McCall an Frei, 1999). Thus, thermal concentration is not a suitable metho prophylactic an nutraceutical components of fruit juices are aversely affecte. centration is a promising metho in fruit juice concentration in which water is remove as ice an not vapor. It can be an alternative to thermal concentration, but the achievable concentration is lower (about 4 g TSS 1 g -1 ) than values obtaine by thermal concentration (6 g TSS 1 g -1 ) (Aier an e Halleux, 28). Cherry an apricot juices were successfully cryoconcentrate to 45 an 35 g TSS 1 g -1, respectively (Aier an e Halleux, 28). Clarification can remove suspene solis an colloial materials of the single strength fruit juice an improve the efficiency of cryoconcentration. Juice clarification is a typical step where ultra-filtration process has for fruit juice concentration, because 1 Department of Foo Science an Technology, Faculty of Agriculture, Urmia University, Urmia, West Azarbaijan, Islamic Republic of Iran. Corresponing author; mehran_normohamapor@yahoo.com 2 Deprtment of Foo Science an Technology, Ayatollah Amoli Branch, Islamic Aza University, Amol, Islamic Republic of Iran. 3 Babol Aab Fruit Juice Factory, Fruit Juice Analytical an Experimental Center, Shahi Salehi Street, Eastern Bane Pey, Babol, Mazanaran, Islamic Republic of Iran. 941

2 Nourmohamapor Omran et al. been successfully utilize for ifferent fruit juices (Cassano et al., 23; Cassano an Drioli, 26 ; Cassano et al., 27 ; He, Ji, an Li, 27). Electro-flotation is a convenient pre-clarification process for fruit juices. It is a soli/liqui separation process that is significantly base on the suspension of particles by gas bubbles generate at the surface of electroes, which are immerse in the fruit juice by the application of a current (Burns et al., 1997). Apple juice was successfully clarifie by electro-flotation an enzymatic treatment better than traitional clarification process (Araya-Farias et al., 28). The objective of this stuy was to assess the effect of integrate clarification process (electro-flotation an ultra-filtration) on the efficiency of cryoconcentration technology for obtaining higher total soluble solis with better nutritional properties. MATERIALS AND METHODS Preparation of Fruit Juices Orange an sour cherry fruits were purchase from a local market in Amol an washe with tap water in orer to remove foreign material from the skin. Then, the juice was extracte by FMC juice extractors with a 2-mm-iameter perforate plate an place in a tank. Extracte juices were 1 an 12 L from 12 an 16 kg sour cherry an orange fruits, respectively. 4 gr kg -1 Na 2 So 3 was ae to single strength juice to avoi browning reactions. Preparation of fruits juices is shown in Figure 1. Electro-flotation Unit An electro-flotation cell was mae for pre-clarification of fruit juices. The flotation cell was square (2 cm by 22 cm tall) an mae of Plexiglas (figure is not shown). A sampling valve was fixe 11 cm above the cell bottom. The cathoe was a stainless steel screen (wire iameter of 2 mm), an was positione horizontally on top of graphite ros forming the anoe. The istance between the two electroes was 1 mm. The anoe was fixe at 1.2 cm above the cell bottom. The anoe's area was 144 cm 2 an the current ensity was calculate by using this area. Electrical wires were attache to the electroes with conuctive resin an then connecte to an external power supply. Electro-flotation cell was mae by a esign suggeste by Araya-Ferias et al. (28). UF Process Orange an sour cherry juices were clarifie by ultra-filtration. The plant, with a 3 l fee tank was equippe with a Kock tubular membrane moule. Its specifications were: type series-cor HFM-251, PVDF, nominal molecular weight cut-off 15 k Da, surface membrane area.23 m 2, average iameter of pores 59 A, pressure operating range bar, temperature operating range ( 55 C ) an ph operating range of Ultra-filtration unit was supplie by Gela foo factory (proucing white Iranian cheese by UF). centration Process Fruit juices clarifie by electro-flotation an ultra-filtration were introuce into a cylinrical container an put in the freezer with circulation of icy air at -1±1 C. A thermocouple was inserte in the center of the cyliner to recor the final temperature of the frozen juices. Thawing proceure was carrie out at room temperature by means of simple gravitational thawing. Fruit juice samples (1 L) were cryoconcentrate. The frozen juices were kept at room temperature uner positive pressure to avoi probable contamination ue to bacterial growth. A little part of the sample was kept for experiment an the remaining was use as fee solution for the secon step of cryoconcentration. Concentrate fruit juices obtaine in the secon step were use as 942

3 centration of Orange an Sour Cherry Juice Figure 1. Processing flow chart of clarifie sour cherry an orange juices into concentrate ones. fee solution for the thir step of cryoconcentration process. After each step, the juices were store for analysis at 1- C in a ark glass bottle. Concentration A three-stage column evaporator (Type PAF 53 S, Zürich an Switezerlan) concentrate orange an sour cherry juices at 7-9 C applying vacuum of 45 mbar an a fee rate of 7 L h -1. Concentrate fruit juices were kept refrigerate at 2 C for further analysis. Sample Analyses Total soluble soli measurement was carrie out using han refractometers (Atago Co., Lt., Tokyo, Japan) with scale range of - 32, 28-62, an 58-9 Brix. For sample analyses, concentrate fruit juices were ilute to single strength fruit juice by istille water. Vitamin C was analyze by oxi-reuction reaction using 2,6- ichlorophenol inophenol for concentrate orange juice. Measurement of ascorbic aci was not applicable by oxireuction reaction for concentrate sour cherry juice ue to coincience of pink color (termination of titration) with the color of sour cherry juice. We use spectrophotometer metho (Pepkowitz, 1943; Robinson an Stotz, 1945) for etermination of ascorbic aci in concentrate sour cherry juice. The measurements were performe by a spectrophotometer at wavelength of 5 nm against xylene. Aroma number was etermine by the metho reporte by Kovalenko (1997). Hyroxymethylfurfural (HMF) was etermine by a metho propose by IFFJP (1984). This metho is base on HMF reaction with barbituric aci an p- toluiin, forming a re compoun. This reaction ha a maximum rate at 3-4 minutes an afterwars, Hyroxymethylfurfural (HMF) content of samples were measure at 55 nm absorbance by spectrophotometer. Total 943

4 Nourmohamapor Omran et al. antioxiant activity (TAA) was etermine by the improve version of 2,2 azinobis iammonium salt assay in which the raical cation is generate by reaction with potassium persulphate before aition of antioxiant that was reporte by Re (1999). Forty-five ml of sample (clarifie an non-clarifie) was prepare to etermine suspene soli content in relation to total juice (w/w %) by centrifuging at 2 rpm (g= 67.27) for 2 minutes. The weight of the settle solis was etermine after removing the supernatant. Statistical Analysis Measurements were replicate (n= 3) for each parameter an reporte as mean value ± stanar error. Statistics was performe on a completely ranomize esign with the analysis of variance (ANOVA) proceure in SAS software. Duncan ' s multiple range test (P<.5) was use to etect ifferences among mean values of various parameters. RESULTS AND DISCUSSION Effect of Electroflotation on UF Analytical measurements on fresh sour cherry an orange juices an in samples coming from ultra-filtration an integrate electro-flotation an ultra-filtration are shown in Table 1. Permeate fluxes of orange juice an sour cherry juices were an L m -2 h -1 uring ultra-filtration process, respectively. Orange an sour cherry juices permeate flux increase from an to an L m -2 h -1, respectively, which were pre-clarifie by electroflotation before UF. As a technological point of view, electro-flotation process increase permeate fluxes by 9.9 an 9.99 L m -2 h -1 for orange juice an sour cherry juice, respectively. As a conclusion, ultra-filtration efficiency increase by pretreatment of fruit juices with electro-flotation. However, the practicality an cost effectiveness of using electroflotationultrafiltration process may be questione. Soli content in flocculation as a function of electroflotation of sour cherry an orange juice is shown in Figure 2. No suspene solis in fruit juices coming from integrate electro-flotation an ultra-filtration were etecte in our experiment. Ultra-filtration was use to remove suspene solis in fruit juices so as to obtain concentrate fruit juices with higher total soluble soli uring cryoconcentration. centration of Samples Clarifie orange an sour cherry juices submitte to electro-flotation an ultra- Table 1. Analytical measurements uring ultra-filtration of electroflotate sour cherry an orange juice an enzymatically treate single strength sour cherry an orange juice. Samples TSS a (Brix) Suspene solis(w/w%) Ascorbic aci (mg l -1 ) TAA b (mm trolox) Sour cherry 14.2± ± ± ±.44 UF permeate 14.17± ± ± ±.11 (sour cherry) UF retentate 15.8±1.4 48± ± ±.24 (sour cherry) Orange 1.24± ± ± ±.76 UF permeate 1.11±.7.97 ± ± ±.84 (orange) UF retentate 11.14±.88 53± ± ±1.4 (orange) UF permeate (EF -orange) 1.7±.91 ND c 34.2± ±1.12 a Total soluble soli; b Total antioxiant activity; c Not etecte, Electro-flotation. 944

5 centration of Orange an Sour Cherry Juice Table 2. Total soluble soli of orange an sour cherry juice uring cryoconcentration a. NO 1 NO 2 NO 3 NO 1 NO 2 NO 3 EF-UF sour cherry juice -1 C -2 C 34.52±.14 e 34.42±.15 e 44.42±.19 c 44.32±.33 c 52.44±.13 a 51.5±.36 a EF-UF orange juice 28.43±.16 g 4.51±.15 c 45.42±.19 a 27.55±.13 h 4.54±.18 c 44.63±.13 b EN-UF sour cherry juice -1 C -2 C 33.1±.32 f 32.23±.7 f 41.8± ± ±.2 b ±.33 b EN-UF orange juice 26.9±.22 i 38.63±.18 e 39.86± ±.2 i 35.8±.14 f 38.75±.22 e a NO 1, 2, 3 are representative of cryoconcentration levels. Mean values of Brix with ifferent letter are significantly ifferent (P<.5) by Duncan's multiple range test. EF-UF an EN-UF are representative of Electroflotation-Ultrafiltration an Enzymatic-Ultrafiltration treatment respectively. filtration (EF-UF) were cryoconcentrate to higher total soluble solis rather than fruit juices which were only clarifie by ultrafiltration an enzymatic treatment. The cryoconcentration process took nearly 1 hours. In our experiment, cryoconcentration of integrate clarifie fruit juices (EF-UF) increase efficiency of this process so that higher total soluble solis were obtaine. Final total soluble solis of fruit juices obtaine uring cryoconcentration are shown in Table 2. All of the main effects, as well as the associate interactions, were significant at the P<.5 level for Brix (f= 2, 59; F= 8,45.588), temperature (f= 1, 59; F= ), metho (f= 1, 59; F= ), temperature metho (f= 1, 59; F= ), temperature Brix (f= 2, 59; F= ), an metho Brix (f= 2, 59; F= ) in cryoconcentration of orange juice. All of the Flocculation flocculation ( (gr) ) Humi humi floc floc Sour Cherry Dry ry floc Orange Figure 2. Humi an ry flocculation as efficiency of electro flotation in removing of suspene solis from single strength sour cherry an orange juice uring electro-flotation. main effects, as well as the associate interactions, were significant at the P<.5 level for Brix (f= 2, 59; F= 2, ), metho (f= 1, 59,;F= ), temperature metho (f = 1, 59; F= ), temperature Brix (f= 2, 59; F= ), an metho Brix (f = 2, 59; F= ) in cryoconcentration of sour cherry juice; but, there was no significant ifference between ifferent temperatures (f= 1, 59; F=.7939 ). Mechanism of centration Metho Water molecules exist in two forms in foostuff: free water an boune water. In low temperature of cryoconcentration, free water is easily frozen an can be remove from fee solution being concentrate. However, boune water oes not freeze an this phenomenon causes lower total soluble soli in cryoconcentrate fruit juices compare to thermal concentration (Aier an e Halleux, 28). Water in the form of boun water can bin to any molecule that has -OH or -NH 2 groups, thereby reucing their mobility (because water molecules surroun them). Consequently, the tenency of these molecules to form crystals ecreases an they can resist freezing at low temperatures. After thawing, this boune water changes into liqui an ecrease the total soluble soli of the juices. Suspene solis incluing pectin, protein, an tannin can surroun water molecules an increase percentage of boune 945

6 Nourmohamapor Omran et al. water. Clarification removes suspene solis of fruit juices. Integrate electro-flotation an ultra-filtration (EF UF) was more effective in removing suspene solis compare to enzymatic an ultra-filtration process. Accoring to Table 1, after ultra-filtration, suspene solis measure.97,.82 an (w/w %) for enzymatic clarifie orange an sour cherry juices an UF-EF clarifie orange an sour cherry, respectively. It means that the UF-EF treatment coul completely remove suspene solis of fruit juices an this le to higher efficiency of cryoconcentration by obtaining higher total soluble soli. Mechanism of Electro-flotation The higher total soluble soli uring cryoconcentration of EF-UF clarifie fruit juices is ue to better removal of suspene solis. In our experiment, fruit juices treate with pectinase enzyme an gelatin were submitte to electro-flotation at 3 C. Polyphenol oxiase enzyme is active in single strength fruit juices in this range of temperature. In the presence of oxygen prouce at the surface of electroes, polyphenol oxias enzyme oxiizes tannin more effectively, proucing oliyomers which are not soluble in fruit juices an can be Vitamin C-Orange brought at the surface by the gas bubbles. This phenomenon was reporte by Mayer an Harel (1979). This oligomer not only can be brought to the surface of the liqui but can also absorb better other colloial matters such as proteins an pectin. As a conclusion, combination of electro-flotation an ultrafiltration processes clarifie juices an eliminate suspene solis better than ultrafiltration process alone, an le to obtaining higher total soluble soli uring cryoconcentration. Effect of Process on Vitamin C an Aroma Number Ascorbic aci content of orange juice concentrate by cryoconcentration (- 1±1 C) an thermal concentration at 27.55±.13, 4.54±.18, 44.63±.13 Brix was ±.17, 34.52±.24, ±.23 an 29.5±.23, ±.21, ±.26 mg l -1, respectively (Figure 3a). All of the main effects as well as the associate interactions were significant at the P<.5 level for Brix (f= 2, 23; F= 7,9.6439), type of concentration process (f = 1, 23; F= 493, ) an Brix type of concentration process (f= 2, 23; F= 81, ). Accoring to Figure 3b, Vitamin C-Sour Vitamin Vit. C C ( mgl (mgl -1-1 ) ) c b a 9 e 6 f 3 e f NO1 1 NO2 2 NO3 3 NO1 1 NO2 2 NO3 3 Process process level Process process level level (a) (b) Figure 3. Ascorbic aci content in concentrate orange juice uring cryoconcentration an thermal concentration. Means with ifferent letter are significantly ifferent (P<.5) by Duncan's multiple range test. NO 1, NO 2, NO 3 are steps of concentration prouce by cryoconcentration at 1 C an thermal concentration process. (Orange juice: 28.43±.16, 4.51±.15, 45.42±.19 Brix an Sour cherry juice: 34.52±.14, 44.42±.19, 52.44±.13 Brix). Vitamin Vit. C ( mgl C (mgl -1 ) -1 ) c b a 946

7 centration of Orange an Sour Cherry Juice vitamin C content of sour cherry juices concentrate at 34.42±.15, 44.32±.33, 51.5±.36 Brix by cryoconcentration (- 1±1 C) an thermal concentration was 1.75±.14, 11.5±.25, 12.56±.23 an, 6.62±.34, 4.5±.23, 3.52±.24 mg l -1, respectively. All of the main effects as well as the associate interactions were significant at the P<.5 level for Brix (f= 2, 23; F= 4.867), type of concentration process (f= 1, 23; F= 1, ), an Brix type of concentration process (f= 2, 23; F= ). The significant ecrease in vitamin C content of the samples concentrate by thermal concentration is ue to sensitivity of ascorbic aci to heat. Our results were in agreement with Qiu et al. (1998) who reporte loss of vitamin C was 7-15% uring heat pasteurization of orange juice, while this loss was less than the other non-thermal treatments (5%) such as pulse electric fiel. Aroma number was better retaine in cryoconcentrate fruit juices than thermally concentrate ones (Figure 4-a&b). All of the main effects as well as the associate interactions were significant at the P<.5 level for the type of concentration process (f= 1, 23; F= 4, ) an type of concentration process Brix (f= 2, 23; F= ) for aroma number of concentrate orange juice, but there was no significant ifference Aroma number A n c An-Sour Cherry b e a f between Brix (f= 2, 23; F=.199). All of the main effects, as well as the associate interactions, were significant at the P<.5 level for Brix (f = 2, 23; F= ), type of concentration process (f= 1, 23; F= 2, ) an Brix type of concentration process (f= 2, 23; F= ) for aroma number of the concentrate sour cherry juice. An-Orange An-Orang NO1 1 NO2 2 NO3 3 NO1 1 NO2 2 NO3 3 Process process level level process level Process level (a) (b) Figure 4. Aroma number (An) in concentrate orange an sour cherry juice uring thermal concentration an cryoconcentration process. Mean values with ifferent letter are significantly ifferent (P<.5) by Duncan's multiple range test. NO 1, NO 2, NO 3 are steps of concentration which are prouce by cryoconcentration at 1 C an thermal concentration process. (Orange juice: 28.43±.16, 4.51±.15, 45.42±.19 Brix an Sour cherry juice: 34.52±.14, 44.42±.19, 52.44±.13 Brix). Aroma number A n Hyroxymethylfurfural Content of Orange Sample (HMF) No significant HMF increase was observe uring cryoconcentration of orange juice (Figure 5). ly concentrate orange juice ha higher HMF content than cryoconcentrate orange juice. However, HMF content was lower than critical limit (< 2 mg l -1 ) in thermally concentrate orange juice. The Association of the Inustry of Juices an Nectars from Fruits an Vegetables of the European Economic Community (AIJN, 1996) has inclue the amount of HMF among the absolute parameters of quality (< 2 mg l -1 ) in the coe of practice for the evaluation of fruits an vegetables juices. Accoring to results, cryoconcentration i not lea to egraation of ascorbic aci to intermeiate reactive proucts ue to low temperature c b e a f 947

8 Nourmohamapor Omran et al. HMF (mgl -1 ) HMF NO1 NO2 NO3 NO 1 NO 2 NO Process level Figure 5. Hyroxymethylfurfural formation (HMF) in concentrate orange juice uring cryoconcentration an thermal concentration process. NO 1, NO 2, NO 3 are steps of concentration which are prouce by cryoconcentration at 1 C an thermal concentration process. (Orange juice: 28.43±.16, 4.51±.15, 45.42±.19 Brix an Sour cherry juice: 34.52±.14, 44.42±.19, 52.44±.13 Brix). applie uring concentration. It has been reporte that several reactive proucts of ecomposition occur via the egraation of vitamin C (Eskin, 199; Hulein et al., 1971) an these compouns may combine with amino acis an result in the formation of brown pigments (Clegg, 1964; Larisch et al., 1998). Total Antioxiant Activity of Orange an Sour cherry Samples Total antioxiant activity (TAA) of cryoconcentrate sour cherry an orange juice i not ecrease significantly (Figure 6), whereas TAA of thermally concentrate sour cherry an orange juices significantly ecrease. All of the main effects as well as associate interactions were significant at the P<.5 level for Brix (f= 2, 23; F= 1.465), type of concentration process (f= 1, 23; F= 2, ), an Brix type of concentration process (f= 2, 23; F= 67.57) in total antioxiant activity of concentrate orange juice. All of the main effects as well as the associate interactions were significant at the P<.5 level for Brix (f= 2, 23; F= ), type of concentration process (f= 1, 23; F= 1, ), an Brix type of TAA (m M trolox) TAA (m M trolox) a a a b TAA- Orange NO1 NO2 NO3 NO 1 NO 2 NO 3 a ab b c TAA- Sour Cherry c Process level NO1 NO2 NO3 NO 1 NO 2 3 Figure 6. Total antioxiant activity (TAA) in concentrate orange an sour cherry uring cryoconcentration an thermal concentration process. Means with the same letter are not significantly ifferent (P<.5) by Duncan's multiple range tests. NO 1, NO 2, NO 3 are similar Brix of concentrate prouce by cryoconcentration at 1 C an thermal concentration process. (Orange juice: 28.43±.16, 4.51±.15, 45.42±.19 Brix an Sour cherry juice: 34.52±.14, 44.42±.19, 52.44±.13 Brix). Process level concentration process (f= 2, 23; F= ) in total antioxiant activity of concentrate sour cherry juice. Results obtaine from comparison of the mean values by Duncan ' s multiple range test showe that cryoconcentrate orange an sour cherry juices ha significantly (P<.5) higher total antioxiant activity than those thermally concentrate. CONCLUSIONS Juices clarifie by electro-flotation an ultra-filtration were better cryoconcentrate 948

9 centration of Orange an Sour Cherry Juice than those clarifie by enzymatic process an ultra-filtration process. Efficiency of cryoconcentration was improve ue to obtaining higher total soluble soli (TSS) in orange an sour cherry juices. Ascorbic aci, aroma number, an total antioxiant activity retention were better preserve in concentrates prouce by cryoconcentration compare to concentrates prouce by thermal concentration. Besies, hyroxymethyfurfural content of thermally concentrate sample (orange juice) was significantly more than cryoconcentrate sample. To our knowlege, we are the first group investigating effect of improve clarification process on efficiency of cryoconcentration process for obtaining concentrate fruit juices with higher total soluble solis. REFERENCES 1. Aier, M. an e Halleux, D. 28. Prouction of Concentrate Cherry an Apricot Juices by centrate Technology. LWT, 17: Araya-Farias, M., Monor, M., Lamarche, F., Tajchakavit, S. an Makhlouf, J. 28. Clarification of Apple Juice by Electroflotation. Innov. Foo. Sci & Emer. Tech., 34: Bailey, A. F. G., Barbe, A. M., Hogan, P. A., Johnson, R. A. an Sheng, J. 2. The Effect of Ultra-filtration on the Subsequent Concentration of Grape Juice by Osmotic Distillation. J. Mem. Sci., 164: Block, G., Norkus, E., Hues, M., Manel, S. an Helzlsouer, K. 21. Which Plasma Antioxiants are Most Relate to Fruit an Vegetable Consumption? Ame. J. Epi., 154: Burns, J., Fras, P. D. an Bramley, P. M. 23. Ientification an Quantification of Carotenois, Tocopherols an Chlorophylls in Commonly Consume Fruits an Vegetables. Phytochem., 62: Burns, S. E., Yiacoumi, S. an Tsouris, C Microbubble Generation for Environmental an Inustrial Separations. Separ. Purif. Tech., 11: Cassano, A., Drioli, E., Galaverna, G., Marchelli, R., Di Silvestro, G. an Cagnasso, P. 23. Clarification an Concentration of Citrus an Carrot Juices by Integrate Membrane Processes. J. Foo Eng., 57: Cassano, A. an Drioli, E. 26. Concentration of Clarifie Kiwifruit Juice by Osmotic Distillation. J. Foo. Eng., 79: Cassano, A., Marchio, M. an Driolli, E. 27. Clarification of Bloo Orange by Ultrafiltration: Analyses of Operating Parameters, Membrane Fouling an Juice Quality. Desal., 212: Clegg, K. M Non-enzymatic Browning of Lemon Juice. J. Sci. Foo Agric., 15: Eskin, N. A. M Biochemistry of Foo Processing: Browning Reactions in Foos. In: "Biochemistry of Foos". Secon Eition, Acaemic Press, Lonon, PP Garner, P. T., White, T. A. C., McPhail, D. B. an Duthie, G. G. 2. The Relative Contributions of Vitamin C, Carotenois an Phenolics to the Antioxiant Potential of Fruit Juices. Foo Chem., 68: John, J, H., Zieblan, S., Yukin, P., Roe, L. S. an Neil, H, A, W. 22. Effects of Fruit an Vegetable Consumption on Plasma Antioxiant Concentrations an Bloo Pressure: A Ranomize Controlle Trial. The Lancet, 359: He, Y., Ji, Z. an Li, S. 27. Effective Clarification of Apple Juice Using Membrane Filtration without Enzyme an Pasteurization Pretreatment. Separ. Purif. Tech., 57: Hulein, F. E., Coggiola, I. M., Sihu, G. S. an Kennett, B. H The Anaerobic Decomposition of Ascorbic Aci in the ph Range of Foos an in More Aci Solutions. J. Foo Agric., 22: Keeney, M. an Bassette, R Determination of Intermeiate Compouns in the Dairy Stages of Browning Reaction in Milk Proucts. J. Dairy Sci., 43: Kovalenko, E Prouction of Fruit Juices by Freeze Concentration Technology. MSc. Thesis, Oessa State Acaemy of Foo Technologies, PP Larisch, B., Groβ, U. an Pischetsrieer, M On the Reaction of L-ascorbic Aci with Propylamine uner Various Conitions: Quantification of the Main Proucts by HPLC/DAD. Zeitscrift fur Lebensmittel- 949

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