4

Alternative Processing
Technologies for the
Control of Spoilage
Bacteria in Fruit Juices and
Beverages

Purnendu C. Vasavada

CONTENTS

Introduction
Control of Microbial Contamination
Preventive Measures in the Orchard
Washing
Preservatives
Pasteurization
Nonthermal Alternative Processing Technologies
High Pressure Processing
Pulsed Electric Field
Ultraviolet Light
Irradiation
Microwaves
Summary
Acknowledgment
References



The FDA also issued regulations dealing with the
warning label on any unpasteurized juices that have not received a 5-log
reduction process and recently, published the Juice HACCP Þnal rule on
January 19, 2001.

6,7

CONTROL OF MICROBIAL CONTAMINATION

Microbial contamination of fruit can occur at all stages of growth, harvesting,
storage, and processing. The surfaces of fresh fruits are often contaminated
with yeasts and molds. The use of over-mature, damaged, or fallen fruit
contaminated with manure from grazing animals has been implicated in

Salmonella

and

E. coli

O157:H7 outbreaks. Control of microbial contami-
nation of fruit and fruit juice involves care at all stages of production,
including preharvest practices of planting, growing of fruit, harvesting, post-
harvest handling, washing, and cooling and storage.

P

REVENTIVE


be prevented, and fertilizing orchards with manure should be avoided.

11

Using “drops” and damaged fruit increases the potential for microbiological
contamination, including contamination with

E. coli,

and therefore should
be avoided.

11–13

Another important source of

E. coli

O157:H7 infections is
drinking water. Waterborne transmission of

E. coli

O157:H7 as a source of
infection in domestic animals is a concern to human health as well. Wang
and Doyle

14

reported that

TABLE 4.1
Effects of Different Chemicals in Reducing Bacteria on the Surface of Fruits

Chemicals/ Disinfectants Concentration
Type of Bacteria
(Inoculum) Sample
Log

10

Reduction

Pathogenic Bacteria

Acetic acid 2–5%
5%

E. coli

O157:H7 Strawberry
Apple
1.6
3.1
Peroxyacetic acid (Tsunami 100) 80 ppm
80 ppm

a

1280 ppm



E. coli

O157:H7

E. coli

O157:H7

Salmonella chester

Strawberry
Tomato
Apple — on skin (cut)
Apple — on stem and calyx (cut)
1.2–2.2
4
3–4
1–2
Chlorine dioxide (Oxine) 5 ppm
80 ppm

E. coli

O157:H7 Apple 3
4.5
Sodium hypochlorite (NaOCl) 100–200 ppm
200 ppm
1.76%


© 2003 by CRC Press LLCTABLE 4.1 (CONTINUED)
Effects of Different Chemicals in Reducing Bacteria on the Surface of Fruits

Chemicals/ Disinfectants Concentration
Type of Bacteria
(Inoculum) Sample
Log

10

Reduction

Phosphoric acid 0.3%

E. coli

O157:H7 Apple 2.9–2.3
Trisodium phosphate 2%

S. chester

Apple 1–2
Produce wash solution A mixture of water, oleic
acid, glycerol, ethanol,
potassium hydroxide,
sodium bicarbonate, citric
acid, and distilled

2

O

2

) (50–60ûC)
Hydrogen peroxide
(H

2

O

2

) + acidic surfactants
(50–60ûC)
(5%)

E. coli

Apple 2.5
3–4

TX110_book Page 76 Tuesday, May 6, 2003 9:21 AM
© 2003 by CRC Press LLC

Sodium hypochlorite (NaOCl) 200 ppm


b

16 times the recommended concentration.
Adapted from references 9, 18, 23–25.

TX110_book Page 77 Tuesday, May 6, 2003 9:21 AM
© 2003 by CRC Press LLC5-log reduction of

E. coli

O157:H7 on apple surface. A 4.5-log reduction of

E. coli

O157:H7 was obtained using chlorine phosphate buffer (3200 ppm)
and chlorine dioxide (80 ppm). Hydrogen peroxide (5% H

2

O

2

) was less
effective in reducing

E. coli


18,19

Conventional washing practices using chlorine and brushing only may
be partially effective in controlling microbial contamination.

9

The pathogens
contaminating the fruit are not always located on the surface

20

and are not
always distributed uniformly, thus limiting the effectiveness of surface treat-
ments. Kenney et al. (2001)

19

suggested that cells may be sealed within
naturally occurring cracks and waxy cuts in platelets. These cells may be
protected from disinfection and subsequently released when apples are eaten
or pressed for cider production. Also, the 5-log inactivation of pathogens on
the surface may not necessarily result in requisite reduction of pathogens in
juice.

21,22

For example, Pao and Davis (1999)


Although sodium benzoate was
more effective than potassium sorbate on

E. coli

O157:H7,

26

the bacteria
survived in refrigerated cider containing 0.1% sodium benzoate for 21

TX110_book Page 78 Tuesday, May 6, 2003 9:21 AM
© 2003 by CRC Press LLCdays.

26

Similarly, citric and malic acids had no bactericidal effect.

27

Comes
and Beelman (2002)

27

indicated that a 5-log reduction of

Dock et al. (2000)

29

stated that addition of sodium benzoate
(0.2%) increased the z-value from about 6 to 26ûC. This increase may result
in a longer 5-log reduction time (higher 5D-values) at higher temperatures
(i.e., 70ûC) in cider with benzoate as compared to cider without additives.
This has profound implications because processors who add benzoate to
cider before processing may obtain less than the 5-log reduction of

E. coli

O157:H7 that would have occurred without any benzoate addition. Induction
of acid resistance can also have wide-ranging effects on the ability of bacteria
to resist other stresses such as heating, antimicrobials, and exposure to
ultraviolet light.

22,30

While preservatives may have some merit for extending
product shelf life, they cannot be relied upon to eliminate pathogens from
fruit juice or cider.
The FDA guideline for minimizing microbiological hazards emphasizes
Þve major areas:
1. Water quality
2. Manure/bio-solids
3. Worker hygiene
4. Field, facility, and transport sanitation
5. Trace back


Salmonella

spp.

Listeria monocytogenes

≥

5
71.1ûC/6 sec Apple cider

E. coli

O157:H7
(cocktail)

Salmonella

spp. (cocktail)

L. monocytogenes

(cocktail)
5
71.1ûC/160ûF
for 11 min
or
76.7ûC/170ûF for 2 min
Apple cider produced from Red

© 2003 by CRC Press LLC