**3.2 Water permeability and permeate fluxes**

304 Food Industrial Processes – Methods and Equipment

L / h x P Bar Flux L.m .h

The water permeability (L.m2.h) was measured with a chronometer, at 10 minutes intervals. Cleanup procedures (alkaline and chlorine-alkaline) were performed before and after each

Membrane alkaline cleaning was performed by adding 80 mL of a NaOH solution (Tedia, Rio de Janeiro, Brazil) (1N/pH 11) to 10 L of distilled water at 40 ºC, and re-circulating the solution in the system for 30 minutes. The solution was then discarded, using 80 L of distilled water. Chlorine-alkaline-cleaning was performed by using 40 mL of NaOH (1N/pH 11) and 130 mL of NaClO (Tedia, Rio de Janeiro, Brazil) (6% sodium hypochloride) diluted in 10 L of distilled water at 40 ºC, with recirculation in the system for 30 minutes,

The juices were clarified in a PROTOSEP IV system (Koch Membrane Systems Inc., Massachusetts, USA) using a 0.3 µm (mean pore diameter) polyethersulfone membrane. For optimization of the best transmembrane pressure to be applied, 8.0 L of conventional

For flux calculation, the volume of the clarified juice was measured each 5 minutes. The best fluxes were obtained at 0.5 Bar TMP, which was used for all the processes, in triplicate.

The whole and clarified acid lime juices were previously lyophilized in a Labconco Lyophilizer (model 75223, Kansas City, Missouri, USA) at - 40 ºC, under vacum (< 200 x 10-3

The Folin-Ciocalteau method (Folin & Ciocalteau, 1927; Singleton & Rossi, 1965) was used for quantification of the total polyphenol in the juices. After reaction with the Folin-Ciocalteau reagent (2N) (Sigma Aldrich, Steinhem, Germany), absorbance was measured at 760 nm (λmax = 765 nm) using a UV- vis spectrophotometer (Shimadzu, model 1240, Kyoto, Japan). The amount of polyphenols was calculated from a standard curve of gallic acid (MP Biomedicals, Ilkirch, France). The results were expressed as mg of gallic acid equivalents

Statistical analysis was performed using one-way ANOVA and mean values were compared applying Duncan's multiple range tests using Minitab Microsoft Excel. Trends were

**3.1 Conventional lime juices (CLJ) and biodynamic organic lime juices (BLJ) yields**  The CLJ and BLJ yielded 52.60 and 44.65%, respectively, in accordance with the minimum yield of 42% recommended by Swisher & Swisher (2000) for citric juices. On the other hand, CLJ yield was significantly higher than that of BLJ (*P* < 0.05), possibly due to the higher

considered significant when means of compared sets differed at *P* < 0.05.

followed by washing with 80 L distilled water. After each cleanup, pH was checked.

acid lime juice was used, operating at 0.5, 1.0 and 2.0 Bar, for 60 minutes.

Where: 0.05 m2 = total membrane area; P = applied transmembrane pressure

process, aiming to recover water permeability of the membrane.

**2.3 Membrane processes 2.3.1 Pressure optimization** 

**2.4 Total polyphenol content** 

(GAE)/mL of juice sample (Andrade et al., 2007).

mBar), for 18 hours.

**2.5 Statistical analysis** 

**3. Results and discussion** 

<sup>2</sup>

0.05 m

2

Mean water permeability flux was 1,241.95 L.m2.h (± 0.48) in the three processes using the 0.3 μm membrane.

In order to determine the best operating transmembrane pressure for all MF processes, 8.0 L of CLJ were initially used in the feed, resulting in 6.0 L (75%) of clarified juice. The mean fluxes obtained at transmembrane pressures of 0.5, 1.0 and 2.0 bar were 49; 47 and 35 L.m2.h, respectively (Fig.2). A slight difference was observed between the fluxes at the applied transmembrane pressures during the first twenty minutes of the process, but after this time there was a significant flux decline for processes operated at 1.0 and 2.0 Bar, demonstrating that concentration polarization was the result of polarization on the membrane surface and/or fouling, providing a decrease in the clarified juice flux over time (60 minutes) in all cases, which was more pronounced at 2.0 Bar. For both UF and MF processes, flux decline is high even when the water permeability of the membrane is completely recovered by washing (Oliveira et al., 2006).

Fig. 2. Effect of process mechanism on the permeate flux at 0.5, 1.0 and 2.0 Bar transmembrane pressures with conventional lime juice.

Thus a 0.5 Bar transmembrane pressure for 60 minutes was adopted to process BLJ by MF, resulting in a mean volume of 6.0 L of clarified juice from a 8.15 L feed and yields of 73, 76 and 54% of clarified juice in the first, second and third processes, respectively (Fig. 3). In the first and third process, after the first 20 minutes there was a decrease in the flux that declined gradually declined until the end of the process, probably due to fouling.

Organic Acid Lime (*Citrus Latifolia* Tanaka) Clarified by Microfiltration 307

301

(Onsekizoglu et al., 2010), orange (Galaverna et al., 2008) and kiwi juices (Cassano, Marchio

The total polyphenol contents of the whole and clarified CL and BL juices were 304 mg/100 g, 336 mg/100 g, 242 mg/100 g and 263 mg/100 g, respectively (Fig. 4). It must be emphasized that the gallic acid calibration curve employed to calculate total polyphenols expressed as gallic acid equivalents (GAE) (mg GA/100 g sample) showed a determination

Fig. 4. Total polyphenol contents in conventional lime (CLJ) and biodynamic lime (BLJ)

Total polyphenols in fruits and juices of fruits of different origins (tropical and exotic) have been investigated for their antioxidant activity. Kuskoski et al. (2005 and 2006) found contents of 897.60, 229.60, 580.10, 544.90, 136.80 and 132.10 mg GA/100 g, respectively, in extracts of baguaçu and jambolão, acerola, mango, açaí and strawberry pulps. Lower total polyphenol contents were found for jambolão, açaí and strawberry extracts (whole juices) than found in the present study for the whole and clarified acid lime juices. Cavalcante et al. (2006) found total polyphenol contents of 119 mg GA/100 g, in the cashew juice, while Mondello et al. (2000) obtained 217 mg GA/100 g in orange juice, 145 mg GA/100 g in caqui, and 134 mg GA/100 g in pineapple, and Gorinstein et al. (1999) found 164 mg

However, much higher levels were reported by Vargas et al. (2008) in red grapes (508.4 mg GA/100 g) and white grapes (487.3 mg GA/100 g) recognized as rich in anthocyanins. Rapisarda et al. (2008) also found higher levels of polyphenols in orange juices (507.01 mg

coefficient (R2 ) of 0.9967, proving a positive correlation (R = 0.9983) (Fig. 5).

and Drioli, 2007) resulting in similar characteristics.

**3.3 Total polyphenol contents** 

whole and clarified juices at 0.5 Bar.

GA/100 g in mango.

GA/100 g).

Fig. 3. Effect of process mechanism on the permeate flux at 0.5 Bar with biodynamic lime juice.

MF processes have been employed to clarify apple (Onsekizoglu et al., 2010), orange and kiwi juices (Galaverna et al., 2008), resulting in the same behavior. The processes presented mean fluxes of 75 L.m2.h, with a progressive and constant decrease until the end (50 L.m2.h). Kozák et al. (2006) and De Paula et al. (2004) using a 0.3 μm tubular membrane (polyesthersulphone) at 0.5 Bar transmembrane pressure in the clarification of strawberry and passion fruit juices, observed higher mean flux reductions of clarified juice (53% and 56%, respectively). Concentration polarization causes the initial decrease in permeate flux and "fouling" results from accumulation of material on the membrane surface reducing flux along the process time.

A different behavior was observed for clarification of pomegranate juice by MF, using hydrophilic mixed cellulose esters flat membranes (Plate and frame system – 0.22 μm), where the flux decreased rapidly in the early stage (10 minutes - 5.0 L.m2.h), remaining constant until the end (Mirsaeedghazi et al., 2010).

Moreover, Yasan et al. (2007) clarified pasteurized apple juice, with prior enzymatic treatment, using a 0.2 μm polyethersulfone flat membrane (Plate and Frame system) obtaining higher than 60 L.m2.h fluxes at 2.0 Bar.

Laorko et al. (2010) used 0.1 and 0.2 μm polysulphone hollow fiber membranes at 1.0 Bar in the clarification of hydrolyzed pineapple juice, obtaining fluxes of 24.2 and 22.0 L.m2.h., respectively. However, it was noticed that the systems used by the aforementioned authors, especially those using flat and sheet membranes, promote faster fouling formation.

Carvalho et al. (2008) obtained a mean flux of 31.37 L.m2.h in clarification by MF of non hydrolyzed pineapple juice, using a 0.3 μm tubular polyethersulfone membrane at 3.0 Bar, while for the UF of the same juice, the mean flux was 17.39 L.m2.h, at 6.0 Bar.

The clarified juices in this study presented light green color and a limpid, translucent and very attractive aspect, as expected. MF processes have been employed to clarify apple (Onsekizoglu et al., 2010), orange (Galaverna et al., 2008) and kiwi juices (Cassano, Marchio and Drioli, 2007) resulting in similar characteristics.
