1. MINIMALLY PROCESSED FOODS (2 Hours) ASSOC PROF DR AZIZAH OSMAN Faculty of Food Science and Biotechnology Universiti Putra Malaysia (UPM) (2 Hours) ASSOC PROF DR AZIZAH OSMAN Faculty of Food Science and Biotechnology Universiti Putra Malaysia (UPM)

2.  Minimally or light processing refers to: l trimming l peeling l sectioningof fruits and vegetables l slicing l coring  Demand for minimally processed (MP) fruits and vegetables has increased due to busy life style increased purchasing power health conscious trends

3. § Consumers are increasingly demanding *convenient, * ready-to-use fruits and *ready-to-eatvegetables *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.

4. 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.

5. § 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 4 - 7 days 21 days at least 4 - 7 days but preferably even longer up to 21 days depending on the market § loss of ascorbic acid and carotenes is the main limiting factor of nutritional quality.

6. §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.

7. 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).

8. §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.

9. Reasons for quality changes in MP produce §MP produce deteriorates because of : * physiological ageing which may result in * biochemical changesdegradation of the colour, * microbial spoilagetexture, flavour of the produce §During peeling and grating operations, * many cells are ruptured * intracellular products such as oxidizing enzymes are released.

10. §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.

11. 1. Physiological and Biochemical Changes §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.

12. Lipoxidase §Another important enzyme which catalyzes peroxidation reactions causes formation of numerous bad smelling aldehydes and ketones

13. Ethylene production §Minimal processing increases ethylene (C 2 H 4 ) production §C 2 H 4 involves in the biosynthesis of enzymes involved in fruit maturation partially responsible for softening of sliced fruit.

14. Respiration 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

15. 2. 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.

16. Factors Affecting the Microbial Stability and Quality of MP Vegetable Salads §Intrinsic factors §Processing factors §Extrinsic factors §Implicit factors

17. Intrinsic 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.

18. Processing Factors §Washing l at harvesting may contaminate produce with water borne microorganism. l At the processing plant should reduce the microbial load §Temperature l blanching reduce/destroy vegetative microbial load l low temperature (0-5 o C) during preparation and storage limits growth of microorganisms.

19. Processing Factors …… continues §Other processes l processing operations such as chopping, shredding, slicing may contaminate the MP produce l assembly of salads may result in contamination from process workers, work surfaces l use of low pH dressings lowers pH l use of packaging to act as O 2 and water barriers and to prevent microbial contamination.

20. Table 1: Effect of unit operations of commercial processing lines on aerobic microbial plate counts from various vegetables (Source Garg et. al (1990)

21. Extrinsic Factors §Temperature *temperature fluctuations during transport and retailing §Modified atmosphere packaging *modified atmosphere packaging influences survival of microorganisms during storage

22. §Benefits of MA cannot be explained solely by a reduction in total microbial number. §There are other influencing factors such as: l packaging material used l relative humidity during storage l type of produce l 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.

23. Implicit Factors §Competition between predominant microbial groups. E.g lactic acid bacteria and pseudomonads §Antagonistic relationships between microbial groups. §Synergism between microbial group

24. Any Questions? To be continued …...