Mechanical and Temperature Effects on Shelf Life Stability of Fruits and Vegetables - Food Shelf Life Stability: Chemical, Biochemical, and Microbiological Changes - page 73

temperature of carrots is 0.6°C with a relative humidity of above 90%. 209 Storage
at high temperature of 21.1 to 26.7°C can cause a weight loss of 10% per day 210
with a marketable shelf-life of only 2 days. At 10°C the weight loss rate is about
1% per day with a marketable shelf life of 2 to 3 weeks. The production of the bitter
tasting compounds isocoumarin and eugenin can be minimized at temperatures near
0°C. 7,211 As for most vegetables, at least 90% relative humidity must be maintained
during storage to avoid weight loss, which can lengthen the storage life of carrots
by up to 50%. 212 The recommended storage and transit temperature of fresh sweet
corn is at 0°C and 95 to 98% relative humidity, since its high respiration rate is one
of the highest of all fruits and vegetables. 208 A common postharvest handling problem
for sweet corn is the loss of sweetness due to a decrease in sugar content, which is
four times less at 0°C than at 10°C. 213 Partial dehusking and shrink-wrapping of the
produce resulted in lower respiration rates and loss of sweetness. 214
Blanching is carried out on peas prior to further canning, freezing, or dehydration
to inactivate enzymes. Common blanching temperatures are 85 to 96°C, while blanch-
ing times are from 2 to 5 min depending upon size and maturity. 71 Blanching may
cause losses of as high as 36% of the ascorbic acid of peas. The higher blanching
temperatures with shorter blanching times are used to minimize these losses. Damaged
peas lose more ascorbic acid during blanching due to oxidation. 215 Other vitamins lost
during blanching are thiamin, niacin, and riboflavin. Rapid freezing of peas is important
to stop deteriorative changes that may develop after harvesting the crop. Frozen peas
are now the common form by which peas can be bought on the retail market. Freezing
can be done by individual quick-freezing (IQF) on a fluidized bed freezer.
NEEDS FOR FURTHER RESEARCH AND DEVELOPMENT
Little information is available for the degree of care required when handling fruits
and vegetables. The often repeated instruction “to handle agricultural products like
eggs” is sometimes irrelevant. According to Liu, 180 due to the different characteristics
of fruits and vegetables, care in handling may vary considerably. Handling products
more gently than eggs may apply to strawberries and raspberries but not to com-
modities that possess tough rinds. Extra care and precautions taken in handling are
expensive, which may not be necessary for some commodities. Information on the
level of compression, abrasion, and impact forces a commodity can withstand and
practices that can cause damage is needed. Such information could be used to design
appropriate packaging materials, handling equipment, and systems without unnec-
essarily adding costs, and for instruction of workers in the field and packinghouse
for proper care in harvesting and handling without unnecessarily adding costs.
There is also a need to develop rapid and reliable non-destructive methods for
detecting damage in order to prevent unnecessary wastage due to sampling and the
resultant condemnation of packages. Present sorting or grading operations require
substantial manpower in removing injured or diseased products. Moreover, manual
sorting or grading is unreliable as it is subject to human errors. Rapid and objective
means of detecting damage and sorting are needed to maintain product quality and
enhance shelf life.