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MINIMALLY PROCESSED FOODS
MINIMALLY PROCESSED FOODS
(2 Hours)
ASSOC PROF DR AZIZAH OSMANFaculty of Food Science and Biotechnology
Universiti Putra Malaysia (UPM)
(2 Hours)
ASSOC PROF DR AZIZAH OSMANFaculty of Food Science and Biotechnology
Universiti Putra Malaysia (UPM)
Minimally or light processing refers to: trimming peeling sectioning of fruits and vegetables slicing coring
Demand for minimally processed (MP) fruits and vegetables has increased due to
• busy life style
• increased purchasing power
• health conscious trends
Consumers are increasingly demanding * convenient,* ready-to-use fruits and * ready-to-eat vegetables* with a fresh-like quality* containing only natural
ingredients
Europe (France & UK) markets for MP fruits and vegetable grow explosively in the start of the 1990’s.
USA - market share of fresh-cut produce accounts for 25% of all produce sales in the retail market.
Minimally processing of raw fruits and vegetables has two (2) purposes:
It is important to keep the produce fresh, yet supply it in a convenient form without losing its nutritional quality.
The product should have a shelf life sufficient to make its distribution feasible to its intended consumers.
In an ideal case, minimal processing can be seen as “invisible” processing
the microbiological, sensory and nutritional shelf life of MP fruits or vegetables should be
at least 4 - 7 days4 - 7 days but preferably even longer up to 21 days21 days depending on the market
loss of ascorbic acid and carotenes is the main limiting factor of nutritional quality.
MP fruits and vegetables are products that contain live tissues or those that have been only slightly modified from the fresh-condition and are fresh-like in character.
The tissues do not exhibit the same physiological responses as the normal (raw) untreated live plant tissues.
Respiration greatly increased in MP fruits and vegetables.
Figure 1: Diagrams of intact and processed (cut) fruit or vegetable cell. (From CTIFL, France.)
Intact cell is expected to be more resistant to oxidative browning and entrance of bacteria compared to the cut cell (MP).
The presence of cut surface complicate the modeling of gas exchange in polymeric package
Figure 2: Diagram of product in package and product with surface modification such as from peeling or slicing. (From CTIFL, France.)A - shows intact vegetable product in a package.B - shows condition of some cut surface cells within the majority of intact interior cell.
Reasons for quality changes in MP produceReasons for quality changes in MP produce
MP produce deteriorates because of :
* physiological ageing which may result in
* biochemical changes degradation of the colour,
* microbial spoilage texture, flavour of the produce
During peeling and grating operations,
* many cells are ruptured
* intracellular products such as oxidizing enzymes are
released.
Main spoilage characteristics indicating loss of quality include:
* development of soft rots
* mould growth
* fermentation
* browning
* production of off-odours
To minimize physiological decay, both quality of raw materials and manufacturing processes must be optimized.
1. Physiological and Biochemical 1. Physiological and Biochemical ChangesChanges
Most important enzyme with regard to MP fruits and vegetables is
polyphenol oxidase (PPO)which causes
browning Enzymatic browning requires the present of four different
components:- oxygen - oxidizing enzyme- copper - a suitable substrate
To prevent browning, at least one of these components must be removed from the system.
LipoxidaseLipoxidase
Another important enzyme which catalyzes peroxidation reactions
causes
formation of numerous bad smelling aldehydes and ketones
Ethylene productionEthylene productionMinimal processing increases ethylene (C2H4)
production
C2H4 involves in the biosynthesis of enzymes involved in fruit maturation
partially responsible for softening of sliced fruit.
Respiration activityRespiration activity Respiration activity of MP produce will increase 1.2
- 7 fold or even more depending on* type of produce* cutting grade* temperature
If packaging condition are anaerobic
leads to anaerobic respiration
formation of ethanol, aldehydes and ketones
2. Microbiological Changes2. Microbiological Changes
Minimal processing damages tissues of produce resulting in leakage of cellular fluids containing nutrients and intercellular enzymes
creates a favourable environment for microbial growth
Minimal processing (peeling, cutting and shredding) expose surface of produce* to air* possible contamination with bacteria, yeast and
moulds.
Factors Affecting the Microbial Stability Factors Affecting the Microbial Stability and Quality of MP Vegetable Saladsand Quality of MP Vegetable Salads
Intrinsic factors
Processing factors
Extrinsic factors
Implicit factors
Intrinsic FactorsIntrinsic Factors pH - varies depending on type of vegetables used.
Nutrient availability- mixed salads contain wider variety of nutrients
than single pack of vegetables.
Biological structure
Other factors- Antimicrobial effects of vegetables Eg antilisterial effect of carrots.
Processing FactorsProcessing FactorsWashing
at harvesting may contaminate produce with water borne microorganism.
At the processing plant should reduce the microbial load
Temperature blanching reduce/destroy vegetative microbial
load low temperature (0-5oC) during preparation and
storage limits growth of microorganisms.
Processing Factors …… continuesProcessing Factors …… continues
Other processes processing operations such as chopping, shredding,
slicing may contaminate the MP produce assembly of salads may result in contamination from
process workers, work surfaces use of low pH dressings lowers pH use of packaging to act as O2 and water barriers and to
prevent microbial contamination.
Table 1: Effect of unit operations of commercial processing lines on aerobic microbial plate counts from various vegetables
(Source Garg et. al (1990)
Extrinsic FactorsExtrinsic Factors
Temperature
* temperature fluctuations during transport and retailing
Modified atmosphere packaging
* modified atmosphere packaging influences
survival of microorganisms during storage
Benefits of MA cannot be explained solely by a reduction in total microbial number.
There are other influencing factors such as: packaging material used relative humidity during storage type of produce type and number of microorganisms present
Combination of low temperature storage and MA packaging has been recommended to enhance quality and to extend shelf life of MP produce.
Implicit FactorsImplicit Factors
Competition between predominant microbial groups.
E.g lactic acid bacteria and pseudomonads
Antagonistic relationships between microbial groups.
Synergism between microbial group
Any Questions?Any Questions?
To be continued … ...
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