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 … ...