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Table 4 Color valuesb and pH of treated and untreated apple juice of 18, 24, 36, 48, and 72 °Brix at 30 and 60 V/cm following ohmic heating

From: Investigation of optimum ohmic heating conditions for inactivation of Escherichia coli O157:H7, Salmonella enterica serovar Typhimurium, and Listeria monocytogenes in apple juice

Voltage gradient

Mean ± SDa

 

Solids content (°Brix)

Treatment time (s)

pH

Colorb

 

L*

a*

b*

30 V/cm

72

0

3.42 ± 0.00

26.47 ± 0.06

0.38 ± 0.01

4.11 ± 0.01

 

60

3.42 ± 0.01

26.44 ± 0.08

0.38 ± 0.02

4.09 ± 0.05

48

0

3.51 ± 0.00

25.43 ± 0.29

0.49 ± 0.03

4.66 ± 0.09

 

60

3.51 ± 0.01

25.47 ± 0.72

0.47 ± 0.11

4.56 ± 0.22

36

0

3.54 ± 0.00

24.85 ± 0.10

0.49 ± 0.04

5.16 ± 0.05

 

60

3.54 ± 0.01

24.76 ± 0.19

0.54 ± 0.02

5.05 ± 0.19

24

0

3.57 ± 0.01

24.72 ± 0.65

0.32 ± 0.04

5.02 ± 0.35

 

60

3.57 ± 0.01

24.55 ± 0.08

0.38 ± 0.01

5.46 ± 0.09

18

0

3.59 ± 0.00

24.23 ± 0.23

0.25 ± 0.02

5.30 ± 0.43

 

60

3.60 ± 0.00

24.51 ± 0.19

0.27 ± 0.02

5.58 ± 0.12

60 V/cm

72

0

3.45 ± 0.01

26.01 ± 0.05

0.37 ± 0.03

4.10 ± 0.11

 

60

3.44 ± 0.00

26.03 ± 0.02

0.36 ± 0.07

4.19 ± 0.08

48

0

3.52 ± 0.01

25.36 ± 0.23

0.47 ± 0.02

4.26 ± 0.06

 

20

3.53 ± 0.00

25.32 ± 0.39

0.46 ± 0.09

4.38 ± 0.15

36

0

3.54 ± 0.01

24.56 ± 0.21

0.49 ± 0.01

5.28 ± 0.08

 

20

3.54 ± 0.01

24.55 ± 0.11

0.52 ± 0.09

5.17 ± 0.02

24

0

3.56 ± 0.00

24.45 ± 0.42

0.36 ± 0.01

5.39 ± 0.31

 

20

3.55 ± 0.00

24.55 ± 0.18

0.37 ± 0.04

5.41 ± 0.19

18

0

3.58 ± 0.01

24.43 ± 0.43

0.28 ± 0.07

5.35 ± 0.03

 

20

3.57 ± 0.01

24.33 ± 0.12

0.27 ± 0.01

5.42 ± 0.10

  1. aResults are expressed as means ± SD. Values in the same column are not significantly different (P > 0.05)
  2. bColor values are L* (lightness), a* (redness), and b* (yellowness)