552 Part V: Fruits, Vegetables, and Cereals
which can activate phospholipase D. Naturally oc-
curring phospholipase D inhibitors such as hexanal
can be used to reduce the activity of phospholipase
D in processed tissues and enhance their shelf life
and quality (Paliyath et al. 2003). The quality of
MPR F&V can be increased by following good
manufacturing practices (GMP), the main points of
which are minimizing handling frequency and pro-
viding continued control of temperature, relative hu-
midity (% RH), and modified and controlled atmos-
phere (MA/CA storage, etc.). Always, the product is
transferred from truck to refrigerated storage imme-
diately to minimize degradative and oxidative reac-
tions. The products are replaced on a first-in–first-
out basis, and the inventory is replaced on a weekly
basis. Currently MPR produce includes the follow-
ing items: ready-to-eat fruits and vegetables, ready-
to-cook fruits and vegetables, ready-to-cook mixed
meals, and fresh ready-to-use herbs and sprouts.
Quality of MPR
Consumers expect fresh-cut products to be of opti-
mum maturity, without defects, and in fresh condi-
tion. The most important physicochemical quality
parameters targeted for preservation include good
appearance, nutrients, and excellent sensory attrib-
utes such as texture, firmness, and taste. Minimally
processed products are vulnerable to discoloration
because of damaged cells and tissues, which become
dehydrated. Cutting and slicing of carrots with a very
sharp blade reduces the amount of damaged cells
and dehydration, when compared with those sliced
with a regular culinary knife. To overcome the prob-
lem of dehydration, fresh-cut produce can be treated
with calcium chloride and kept in a high-humidity
atmosphere. Enzymatic browning is a serious prob-
lem with minimally processed produce. During the
processing of produce, several types of oxidative
reactions may occur, leading to the formation of oxi-
dized products. These reactions cause browning
reactions, resulting in the loss of nutritional value by
the destruction of vitamins and essential fatty acids.
In lipid-rich vegetables, oxidative processes lead to
the development of rancid off-flavors and sometimes
to toxic oxidative products (Dziezak 1986). There
are a number of chemicals used to stabilize MPR
produce, including (1) free radical scavengers such
as tocopherols, (2) reducing agents and oxygen
scavengers such as ascorbic acid and erythorbic
acid, (3) chelating agents such as citric acid, and (4)
other secondary antioxidants such as carotenoids.
Ascorbic acid is commonly used either alone or in
combination with other organic acids. Among the
factors influencing the general quality of MPR pro-
duce, temperature is the most important. When tem-
perature increases from 0 to 10°C, respiration rate
increases substantially, with Q 10 ranging from 3.4 to
8.3 among various fresh-cut products. With the
increase in respiration rate, deterioration rate also
increases at a comparable rate; therefore, low tem-
perature storage is essential for maintaining good
quality (Watada et al. 1996). Modified atmosphere
(MA) within MPR containers or bags is useful in
maintaining the quality of the produce (Gorny
1997). Gas mixtures suitable for MA storage have
been shown to be the same as those recommended
for the whole commodity (Saltveit 1997). A con-
trolled atmosphere (CA) system is used to simulate
the MA, with similar gas composition. A mixture of
10% O 2 10% CO 2 has been shown to retard
chlorophyll degradation in parsley (Yamauchi 1993).
An atmosphere of 3% O 2 10% CO 2 was beneficial
for fresh-cut iceberg lettuce, slightly beneficial for
romaine lettuce, and not beneficial for butterhead let-
tuce (Lopez-Galvez et al. 1996). The oxygen level
can be allowed to drop to the level of the respiratory
quotient breakpoint. The O 2 level could be dropped
to 0.25% for zucchini slices (Izumi et al. 1996) and
0.8% for spinach (Ko et al. 1996).REFERENCES
FURTHERREADINGMATERIALSArthey D, Ashwurst PR. 2001. Fruit Processing: Nu-
trition, Products and Quality Management. Aspen
Publishers, Gaithersburg, Maryland. 312 pages.
Enachescu DM. 1995. Fruit and Vegetable Processing.
FAO Agricultural Services Bulletin 119. FAO. 382
pages.
Jongen WMF. 2002. Fruit and Vegetable Processing:
Improving Quality (Electronic Resource). CRC, Boca
Raton, Florida.
Salunkhe DK, Kadam SS. 1998. Handbook of Vegeta-
ble Science and Technology: Production, Composi-
tion, Storage and Processing. Marcel Dekker, Inc.,
New York. 721 pages.