Chilling Injury and Browning of Fresh-cut Fruits and Vegetables Chien Yi Wang Produce Quality and Safety Laboratory Plant Sciences Institute U. S. Department of Agriculture Beltsville, Maryland 20705 U. S. A.
Fresh-cut
Convenient Fresh Good flavor Nutritious 12 Billion dollar industry annually in the United States.
Fresh-cut
Fresh-cut
Challenges What are the challenges? What kind of problems we can encounter? What kind of approaches we can use to alleviate the problems? Are those approaches safe?
Browning and decay are two of the most serious problems in fresh-cut Products.
Wounding and oxidation cause an increase in metabolic activities and lead to rapid browning of the cut surface Sulfite compounds (e.g. sodium bisulfite,, potassium metabisulfite) ) were banned for use on fresh fruits and vegetables by FDA Alternatives: Other GRAS substances or naturally occurring compounds
Digging for Answers
Natural Products as Anti-browning Agents Cysteine or acetylcysteine An inhibitor of polyphenol oxidase (the key catalytic enzyme in browning reaction.) Ascorbic acid or isoascorbate A reducing agent 4-Hexylresorcinol A competitive inhibitor of polyphenol oxidase.
Anti-browning Treatment Apples acetylcysteine + isoascorbate + 4-hexylresorcinol 4 + calcium propionate Bananas acetylcysteine + citric acid Mangoes isoascorbate + 4-4 hexylresorcinol + potassium sorbate Peaches isoascorbate + 4-4 exylresorcinol + potassium sorbate
Anti-browning Treatments Pears isoascorbate + 4-4 hexylresorcinol + potassium sorbate Pineapples ascorbic acid or isoascorbate Potatoes acetylcysteine + 4-4 hexylresorcinol + citric acid Radishes acetylcysteine + 4-4 hexylresorcinol + potassium sorbate Sweet Potatoes acetylcysteine + citric acid
Fresh - cut Apple Slices
Fresh-cut Apple Slices acetylcysteine + isoascorbate + 4-hexylresorcinol 4 + calcium propionate
Fresh-cut Peach Slices
Fresh-cut Peach Slices isoascorbate + 4-hexylresorcinol4 + potassium sorbate
Fresh-cut Banana Slices
Fresh-cut Banana Slices acetylcysteine + citric acid or glutathione + citric acid
Fresh-cut Sweet Potatoes
Fresh-cut Sweet Potatoes acetylcysteine + citric acid
Fresh-cut Mango Slices
Fresh-cut Mango Slices isoascorbate + 4-4 hexylresorcinol + potassium sorbate
Fresh-cut Pineapple Slices Decay index 5 4 3 2 1 9 Control AIA 0.1 M AC 0.05 M AA 0.05 M A B Up 50% surface affected 20 to 50% surface affected 5 to 20% surface affected Up to 5% surface affected None Freshly-cut 7 Very good Acceptability 5 Limit of marketability 3 Limit of usability 1 Inedible 4 C Browning index 3 2 1 7 14 Days at 10 C
MYTH Fresh-cut products do not have chilling injury problem. Fresh-cut products are less susceptible to chilling injury.
FACTS Fresh-cut products are as sensitive to chilling injury as intact produce Chilling injury symptoms are not evident because of the removal of skin which carries the visible symptoms The affected tissues can develop off- flavor or off- odor which are not visible Chilling temperatures can weaken chilling-sensitive tissues and cause them to be more susceptible to physiological and pathological deterioration
Alleviation of Chilling Injury in Fresh-Cut
Decay induced by chilling injury can be Reduced by UV-C irradiation
UV-C Treatment of Mango Slices
UV-C
Chilling injury can also be reduced by treatment with GRAS (Generally Recognized as Safe) substances, such as methyl jasmonate.
MJ Reduces Chilling Injury
Control MJ-Treated
Control MJ-Treated
Control MJ-Treated
Control MJ-Treated
Control MJ-Treated
Control MJ-Treated
Control MJ-Treated
Decay (%) 120 100 80 60 40 control AITC MJ Alc TTO 20 0 2 4 6 8 10 12 14 Days
Now let me think..what could be the mechanisms through which MJ works to exert its effects?
Antioxidant Activity (ORAC)
Accumulation of HSP 17.6 in Different Pretreated Tomato Fruit During Chilling Temperature Storage Treatment Days of storage at 5 o C 0 1 3 7 14 21 28 Control 38ºC MeJA MeSA 26S rrna
HSP 70-1 1 (Cytosol) transcripts in different pretreated tomato fruit during chilling temperature storage Days of storage at 5 o C Treatment 0 1 3 7 14 21 28 Control 38ºC MeJA MeSA
PR-2B transcripts in different pretreated tomato fruit during chilling temperature storage Days of storage at 5 o C Treatment 0 1 3 7 14 21 28 Control 38ºC MeJA MeSA 26S rrna
Enhanced Expression of 1.5-kb and 3.5- kb AOX Transcripts by 10-4 M MeJA in Cold-Stored Peppers Treatment Air 10-5M MeJA 10-4M MeJA Time (days) 0 1 2 6 14 17 19 1 2 6 14 17 19 1 2 6 14 17 19 ( C) 7 25 0 20 25 0 20 25 0 20 3.5 kb 1.5 kb 18S
Methyl Jasmonate & Methyl Salicylate 1. Are they safe to use? 2. Are they toxic? 3. Are they carcinogenic?
FDA (Food and Drug Administration) EAFUS (Everything Added to Food in the US) GRAS (Generally Recognized As Safe) Document Document Type Number Methyl Jasmonate ASP* 0980 Methyl Salicylate ASP 1600 *Fully up-to-date toxicology information has been sought.
Conclusions Browning and decay are two of the most serious problems in fresh-cut Browning can be prevented by treatment with naturally occurring inhibitors of PPO Fresh-cut products are not immune from chilling injury, except that the injury is expressed in different forms Decay induced by chilling injury can be reduced by UV-C irradiation or by GRAS treatment Methyl jasmonate appears to reduce decay and chilling injury through enhancing defensive gene expression and increasing antioxidant activity
Conclusions (Continue) Increase phenolic acid and anthocyanin in lettuce Increase biosynthesis of flavonols (Quercetin-3- rutinoside, Quercetin-3-diglucoside and Quercetin-3-glucosylrutinoside) in potato Decrease ascorbic acid and increase dehydro- ascorbic acid in pineapple, kiwi, cantaloupe and mango Decrease total carotenoids in cantaloupe, mango, and pineapple Effect on phytonutrients is variable because of wounding stress and oxidation.
Keep improving... To maintain better quality of fresh-cut products. To develop better methods for reducing browning, decay, and chilling injury. Keep improving...