Produce Degradation Pathways and Prevention

Mechanisms of Food Additives, Treatments, and Preservation Technology 311

enzymatic changes that occur in fruits and vegetables and are inhibited by general
antibrowning treatments. PPO browning is usually more severe and most treatments
to prevent browning involve inactivating PPO or reducing the enzymatic activity.
In theory, PPO-catalyzed browning of vegetables and fruits can be prevented by:

• Selection of raw material to minimize enzymatic activity based on factors
  such as maturity level and environmetal factors


• Genetic modification
  
  
  • blocking the gene expression of PPO in plant tissues by antisense RNA
    (Martinez and Whitaker, 1995)
  
  
  
  


• Exclusion or removal of one or both substrates
  
  
  • removing polyphenol by sorption on insoluble poly(vinyl polypyrroli-
    done), poly(ethylene glycol), or other sorbents (Osuga et al., 1994)
  
  
  • exclusion of oxygen by vacuum or MAF packaging, coating (edible)
    and wraps, processing in an inert gas atmosphere, treatment in water
    or brine, efficient deaeration, etc.
  
  
  
  


• Inactivation or inhibition of enzymes
  
  
  • heat inactivation of enzymes (blanching)
  
  
  • treatment with browning inhibitors
  
  
  
  

FIGURE 10.1Browning of apple slices 3 h after treatment by dipping in solution of inhibitor
for 3 min. The degree of browning is expressed as a L value (initial L value – L value after
3 h). (Adapted from Son, S.M. et al., Food Chem., 73, 23, 2001.)

0 5 10 15 20

Without treatment

delta L value

Sodium sulfite (0.5%)

Cysteine (1%)

N-Acetyl-cystein (1%)

Glutathion (1%)

Ascorbic acid (1%)

Ascorbic acid-2-phosphate (1%)

Citric acid (1%)

Oxalic acid (1%)

Kojic acid (0.1%)

p-Coumaric acid (0.1%)

4-Hexylresorcinol (0.1%)