Transcript 3- Fresh-cut fruits and vegetables

Packaging of fresh
fruits & vegetables
Introduction
Fruits and vegetables are consumed in fresh, minimally processed,
and processed forms (canned, frozen, dried, preserves, and fermented
products).
Raw material quality influences the quality of processed fruit and
vegetable products.
Quality evaluation consists of measurement of appearance, texture,
flavor, nutritive value, and safety of the produce.
Safety aspects need to be considered first before all other quality
attributes.
Being live, quality of fruits and vegetables is directly related to the
physiological status and a host of other factors such as diseases and
pests, mechanical injuries, and exposure during postharvest handling
Preharvest factors
Diseases, insects, and pests
Genetic, climatic, and cultural
Physiological
Harvesting factors
Harvesting method,
stress, maturity
Status Respiration,
water loss ripening,
and senscence,
disorders
Quality
Color, flavor,
texture, appearance
Postharvest factors
Storage temperature,
humidity, atmosphere
composition, light, stress
Mechanical injuries
Postharvest Handling Operations
1-Sorting and Grading
 Have a role in protecting and enhancing product quality.
 These are generally an important part of field or packinghouse
operations(storage, transport, distribution, marketing, and processing).
 The produce is sorted according to size, shape, color, and
appearance.
Grading determines whether the product meets a specific quality
standard prescribed by local or international market.
Traditionally, sorting and grading are done by hand
Color is a key sorting parameter
Farm
Farm storage
Transportation
processing shed
Storage
Sorting & Packaging
processing
Transportation
storage
transportation & shipping
Marketing
Consumer
Raw Material Quality Specifications for Processed Fruits
and Vegetables
Processed Products
Raw Materials
Quality Specifications
Fruit juices
Citrus, apple, tomato
Acidity, sugar content, flavor
Chips and fries
Potato , banana,
taro Texture, starch content, R Sugar
Canned products
Apple, peach, pear
Color, texture, flavor
Preserves
Various apple, peace
Pickles
Cucumber, olive, cabbage
Concentrates: sauce, puree
Tomato, apple
Sugar, pectin content, acidity
Composition, sugar content, texture
Total solids
Alcoholic beverages Grape,
apple Fermentable
sugar, acidity
Dried products
Mango, apricot
solid content
Frozen products
Pea, carrot, onion
color, texture, flavor
2- Packaging
Packaging contributes greatly to efficient marketing of fruits
vegetables as it:
1-serves as an efficient handling unit
2-provides convenient
3-protects quality and reduces waste
4- provides service and sales motivation
5-reduces cost of transport and marketing
6-facilitates use of new modes of transportation
Two types of packaging are common in fresh produce trade :
1-Large-sized containers are used for transport and wholesale.
2- small-sized packagers for retail trade.
and
Proper packaging can protect fresh produce from the environment,
such as sunshine, moisture, and light.
The main purpose of packaging is to provide protection from
mechanical damage.
The container must be strong enough to withstand stacking and
impact of loading and unloading, without bruising or scarring the
produce.
The choice of packaging material is based on the requirements of
stacking height, duration of storage, pretreatments, cooling, and cost.
Modified atmosphere packaging
of
fresh produce
 MAP technology is largely used for minimally processed fruits and
vegetables including fresh, ‘‘ready-to-use’’ vegetables.
 MAP is a technique used for prolonging the shelf-life period of fresh
or minimally processed foods.
 In this preservation technique the air surrounding the food in the
package is changed to another composition.
 MAP is used with various types of products, where the mixture of
gases in the package depends on the type of product , packaging
materials and storage temperature.
But fruits and vegetables are respiring products where the
interaction of the packaging material with the product is important.
One of the primary effects of MAP is a lower rate of respiration,
which reduces the rate of substrate depletion.
Ethylene (C2H4) is a natural plant hormone and plays a central role in
the in intiation of ripening, and is physiologically active in trace
amounts (0.1 ppm).
C2H4 production is reduced by about half at O2 levels of around
2.5%.
This low O2 retards produce ripening by inhibiting both the production
and action of C2H4.
 metabolic processes such as respiration and ripening rates are
sensitive to temperature.
 Biological reactions generally increase two to three-fold for every 10
C rise in temperature.
 Temperature control is vitally important in order for a MAP system
to work effectively.
Film permeability also increases as temperature increases, with CO2
permeability responding more than O2 permeability.
 Low RH can increase transpiration damage and lead to desiccation,
increased respiration, and ultimately an unmarketable product .
 One serious problem associated with high in-package humidity is
condensation on the film that is driven by temperature fluctuations.
For most commodities light is not an important influence in their
post-harvest handling.
 However green vegetables, in the presence of sufficient light, could
consume substantial amounts of CO2 and produce O2 through
photosynthesis.
Gases used in modified atmosphere packaging
The three main gases used in modified atmosphere packaging
are CO2, O2 and N2.
 The choice of gas is very dependent upon the food product being
packed.
Used singly or in combination, these gases are commonly used to
balance safe shelf-life extension with optimal organoleptice properties
of the food.
1- Carbon dioxide
Carbon dioxide is a colourless gas, asphyxiant and slightly corrosive
in the presence of moisture, dissolves readily in water.
The high solubility of CO2 can result in pack collapse due to the
reduction of headspace volume.
In some MAP applications, pack collapse is favoured, for example in
flow wrapped cheese for retail sale.
2- Oxygen
 Oxygen is a colourless , odourless gas that is highly reactive and
supports combustion.
 Oxygen promotes several types of deteriorative reactions in foods
including fat oxidation, browning reactions and pigment oxidation.
 to increase shelf life of foods the pack atmosphere should contain a
low concentration of residual oxygen.
3- Nitrogen
Nitrogen is a relatively un-reactive gas with no odour , taste, or color.
 Nitrogen does not support the growth of aerobic microbes and
therefore inhibits the growth aerobic spoilage but does not prevent the
growth of anaerobic bacteria.
 The low solubility of nitrogen in foods can be used to prevent pack
collapse by including sufficient N2 in the gas mix to balance the volume
decrease due to CO2 going into solution.
4- Carbon monoxide
 Carbon monoxide is a colourless, tasteless and odourless gas that is
highly reactive and very flammable.
 It has a low solubility in water but is relatively soluble in some
organic solvents.
Commercial application has been limited because of its toxicity and
the formation of potentially explosive mixtures with air.
5- Noble gases
 The noble gases are a family of elements characterized by their
lack of reactivity and include (He), ( Ar ) , ( Xe ) and ( Ne ).
 These gases are being used in a number of food applications now
e.g. potato-based snack products.
 It is difficult to see how the use of noble gases would offer any
preservation advantages compared with N2 they are being used.
MAP applications
1- Vegetables
 An important fact when dealing with vegetables is that they are still
‘‘living’’ structures and continue to respire as long as there are nutrients
and gases available.
 Water loss is loss of saleable weight and thus a direct loss to the
grower or processor.
A loss in weight of only 5% will cause many vegetables to appear
wilted or shriveled, and under warm, dry conditions without the correct
packaging this can happen in a few hours.
Packaging films can achieve significant increase in shelf life by
reducing the loss of the vegetables’ stored energy reserves through
lowering the respiration rate.
 LDPE was found as good alternative to PVC for wrapping
vegetables.
2- Fruit
 One of the major benefits of MAP is the prevention or retardation of
fruit ripening and associated biochemical and physiological changes.
 Temperature is the most effective environmental factor in the
prevention of fruit ripening.
 Both ripening and C2H4 production rates increase with an increase in
temperature.
 To delay fruit ripening, fruits should be held as close to 0 C as
possible, without suffering chilling injury.
The use of MAP as a supplement to proper temperature
maintenance in the effort to delay ripening is consequentially more
effective for chilling sensitive fruits, but is generally beneficial for all
fruits.
 Reducing O2 concentration below 8% or elevating
CO2 concentration above 1% retards fruit ripening.
 It has been established that 2% O2 level anaerobic respiration may
result in the development of off-flavours and off-odours.
 Fruits exposed to such low O2 levels may also loose their ability to
attain uniform ripeness upon removal from MAP.
 Successful applications of MAP on fruits include Royal Gala apples,
Granny Smith apples, lemons (whole peeled/ sliced), and oranges
(whole, peeled, and sliced).
The effectiveness of modified atmospheres and packaging materials
on the growth of Penicillium expansum and patulin production.
 PE is an excellent packaging material for the storage of apples since
it inhibited the growth of P. expansum , thereby allowing patulin to be
produced.
3- Fresh-cut fruits and vegetables
Demand for fresh-cut fruit and vegetables has been increasing in
recent years, mainly because consumers look for freshness and
convenience when they purchase these commodities. Packaged freshcut vegetables are becoming more and more popular because they
offer several advantages. These products are perceived by consumers
to be more nutritious, convenient, and efficient in terms of meal
preparation (ready-to-eat)
In general, fresh-cut products have a short shelf life, which is
mainly due to mechanical stresses.
At the cut surface, cells and membranes are damaged leading to
alterations in tissue metabolism .
 Although these alterations are different, many authors
have observed an increase in carbon dioxide and ethylene evolution,
water loss, alterations in flavor and aroma, in volatile profiles, and
increase in the activity of enzymes related to enzymatic browning .
 The difficulties encountered with fresh-cut fruit, while not
insurmountable, require a new and higher level of technical and
operational sophistication.
Post-harvest quality loss is primarily a function of respiration, onset
or progression of ripening water loss (transpiration), enzymatic
discoloration of cut surfaces, decay (microbial), senescence and
mechanical damage suffer during preparation, shipping, handling and
processing .
 Extended shelf life was observed in fresh-cut mangoes, pineapples,
and mixes packaged in PET due to reduced O2 and elevated CO2
atmosphere.
The results suggest that shelf life of fresh-cut fruit could be extended
using appropriate semi-rigid containers.
 Increased water activity and mixing of intracellular and intercellular
enzymes and substrates may also contribute to flavor and texture
changes .
 Successful applications of MAP on the quality of some fresh-cut
food include :mushroom, tomato , pineapple , lettuce , potato , …..
 Degradation of cut vegetables in terms of appearance was delayed
by N2 gas packaging.
 Fresh-cut products often have significantly different packaging
requirements than the whole product.
 The MA packaging technique consists of the enclosure of
Respiring
produce in polymeric films in which the gaseous
environment is actively or passively altered to slow respiration, reduce
moisture loss and decay and/or extend the shelf life of the products.
Properties of packaging films.
Material
Paper
Aluminum foil
Cellulose film
Polythene
hydrochloride
Cellulose acetate
Vinylidene chloride
Properties
Strength; rigidity; opacity; printability.
Negligible permeability to water vapour , gases and odours; grease proof, opacity
and brilliant appearance, stability; dead folding characteristics.
Strength; attractive appearance; low permeability to vapour gases,
Durability; heat-sealability; low permeability to water
good chemical resistance; good low-temperature performance.Rubber
Heat-sealability; low permeability to water vapour, gases,odours
Strength; rigidity; glossy appearance; printabilitydimensional stability
Low permeability to water vapour, gases, copolymer odours
and greases; chemical resistance; heat-sealability.
Polyvinyl chloride
Polyethylene tetraphthalate
Resistance to chemicals, oils and greases; heat-sealability
Strength; durability; dimensional stability; low permeability
to gases, odours and greases
Conclusions
1. The greatest extension of shelf life occurs at the lowest possible
oxygen concentration before anaerobic respiration is initiated.
2. The recommended percentage of O2 in a modified atmosphere
for fruits and vegetables for both safety and quality falls
between 1 and 5%, although the oxygen level will realistically
reach levels below 1% in MAP produce.
3- These physiological changes may be accompanied by flavor loss, cut
surface discoloration, color loss, decay, increased rate of vitamin
loss, rapid softening, shrinkage and a shorter storage life.
4- proper temperature management during product preparation and
refrigeration throughout distribution and marketing is essential for
maintenance of quality.
5-To provide packaging films with a wide range of physical properties,
many of these individual films are combined through processes like
lamination and co-extrusion.
6-Polyethylene is most commonly used to provide a hermetic seal and
also as a medium of control for characteristics like anti-fogging
Abilities .
7- The degree to which atmospheric modification takes place in
packages is dependent upon several variables such as film permeability
to O2 and CO2, product respiration and the influence of temperature
on both of these processes .
8-Temperature and headspace atmosphere are two important
factors to prolong shelf life. Modified atmosphere packaging (MAP)
can be interpreted as a dynamic system with two gas fluxes, the
respiration rate of the fresh product and the gas exchange through the
barrier
9. Successful control of both product respiration and ethylene
production and perception by MAP can result in a fruit or
vegetable product of high organoleptic quality Maintaining proper
storage temperatures is often most difficult at retail level.
10. Oxygen, CO2, and N2, are most often used in MAP/CAS. Among
them, CO2 is the only one with a direct antimicrobial effect .
11-It was clear that temperature fluctuation, even if it should occur only
once, can seriously compromise the benefits of modified atmosphere
packaging and safety of the packaged produce.
References
1-M Shafiur Rahman - Handbook of Food Preservation
2- Sandhya ,Krishi Vigyan Kendra, Punjab Agricultural University, Samrala, Ludhiana,
India.(2010). Modified atmosphere packaging of fresh produce: Current status and future
needs. LWT - Food Science and Technology
3- Nitaigour P. Mahalik and Arun N. Nambiar .(2010). Trend in food packaging and
manufacturing systems and technology. Trends in Food Science & Technology
4- Kata Galic , Mario Scetar and Mia Kurek.(2011). The benefits of processing and packaging.
Trends in Food Science & Technology
5- A. Lucera a, C. Costa a, M. Mastromatteo c, A. Conte a,b, M.A. Del Nobile. (2010). Influence
of different packaging systems on fresh-cut zucchini (Cucurbita pepo). Innovative Food Science
and Emerging Technologies
6- Kablan Tano, Mathias K. Oul´e, Gilles Doyon, Robert W. Lencki, Joseph Arul . (2007).
Comparative evaluation of the effect of storage temperature fluctuation on modified
atmosphere packages of selected fruit and vegetables. Postharvest Biology and Technology