food processing technology & hygienic...

1

Food Processing Technology & Hygienic Practices

2

Outlines• What is food technology?• What is a process?• What is an unit operation?• Selected unit operations?

– Blanching– Pasteurization– Sterilization– Dehydration

• Hazard Analysis and Critical Control Point (HACCP)– What are the 7 principles in HACCP?– What are the stages involved?

• What are the packaging materials and their characteristics?

• What are the requirements of the food labeling on the prepackaged food?

3

Food Technology (食品技術) application of the principles and facts of science, engineering , and mathematics to processing, preservation, storage, and utilization of foods.

Food Science (食品科學) deals chiefly with the acquiring of new knowledge to elucidate the course of reactions or changes occurring in foods whether natural or induced by handling procedures.

4

Process (加工處理): sum of all the unit operation involved

Unit operation (操作單元 ) : step/procedure having a specific, identifiable and predictable effect on food, e.g. materials handling, cleaning, separating, disintegrating, pumping, mixing, heat exchanging, evaporating, drying, forming, packaging, controlling, etc.

5

Example of process block diagram (PBD)Tomato-paste-processing plant

washing

Inspection

Pulping

Finishing

Evaporation

Sterilization

Aseptic Packaging

Tomatoes

Storage

Product

water

steam

steam

steam

packages

waste

waste

waste

water

6

What is Blanching?•heat treatment to tissue system prior to freezing, drying and canning

Purposes of Blanching•enzyme inactivation•reduction of surface microorganisms on food•softening vegetables•removal of air

7

Enzymes •lipoxygenase•polyphenoloxidase•polygalacturonase•chlorophyllase

Purposes of Blanching

8

Hot-water Blancher

•food kept in water at 70-100°C for specific time•dewatering and cooling•different designs (examples):>reel blancher>blancher-cooler

http://www.heiusa.com/equipment/sub/rotary-hot-water-reel-blanchers.php

9

What is Heat Sterilization?· Unit operation requiring high temp. and

long time to achieve “commercial sterilization”

· aims to destroy microbial and enzyme activities

· results in:-longer shelf-life (>6 mth)-substantial changes in nutritional and

sensory qualities=>necessary to reduce the changes by

reducing the processing time

10

What is commercial sterilization ?

•a concept of the probability of survival of one microbe

•even with vast majority of sterile containers, there is a probability that non-pathogenic cells survive the heat treatment in a pre-determined number of containers

11

D-value

Fellow, 1990

12

Fellow, 1990

13

Major factor that affects the heat resistance of microbes•pH of food:

-low acid (>pH 4.5)-more acidic (pH 3.7-4.5)-acidic (pH 3.7 >)

14

What serves as norm at different pH?

•low acid food-Clostridium botulinum

•more acidic food-fungi and enzymes

•acidic food-enzymes

15

Types of sterilization• in-container sterilization• ultrahigh temperature processing

16

Retorting (heat processing)

3 methods:-saturated steam-hot water-flames

17

UHT Process•advantages:

-shelf-life of at least 6 months without refrigeration

-processing conditions independent of container size

-cheaper packaging-higher productivity-higher energy efficiency

•disadvantages:-cost and complexity of sterile plant

18

Features- UHT processing•food: heat in continuous heat exchanger

cool in another heat exchanger/vac. chamber•container: unnecessary to withstand

sterilization temp as food•laminated cartons: economic advantages•sterile filling environment:

enclosed filling machine under UV light & filtered airpositive pressure during fillingpre-sterile carton with hydrogen peroxide

19

Classification of UHT process equipment

•direct systems

•indirect systems

20

What is dehydration (脫水) ?•unit operation to vaporize and remove large amount of water in food by the application of heat

Purpose of dehydration•to extend the shelf-life of foods by reduction in water activity

Other related benefits•microbial growth•enzyme activity •volume, product weight

21

What is the mechanism (機制) of drying?•water evaporates and is carried away from the food surface after acquiring sufficient amount of heat from the moving hot dry air => region of low water vapour pressure (蒸汽壓力) Vs that of interior =>establish water vapour gradient (梯度)which is the driving force of drying

Fellow, 1990

22

Characteristics of air for effective drying at constant rate period

•dry-bulb temp•air velocity- affect film thickness•relative humidity

http://www.ardenstone.com/photos/winterhike03/01_thermometer.jpg

http://www.instruments4hire.co.uk/images/airflow-AV6-Air-Velocity-Flow-Temperature-Logger.jpg

http://www.escience.ca/GFX/PRODS/Prod848N634.jpg

Anemometer 風速計

23

Classifications of Driers (乾燥器)

• hot-air driers: bin dryer (deep-bed driers); cabinet driers(tray driers); spray driers, etc.

• heated-surface driers: drum drier (roller driers)

http://www.creeksideequicenter.com/forsale/grainbin/grain_bin.jpg

24

Figure of Tray Drier Schematic

25

Spray Driers (噴霧乾燥機)1. types of foods: fine dispersion of pre-concentrated

food2. atomiser (霧化器)3. advantages: rapid drying in 1-10 s; min. heat

damage, large scale continuous drying, low labourcosts, simple operation and maintenance

http://www.niro.dk/ndk_website/niro/cmsdoc.nsf/WebDoc/ndkk5jrghvKaolinSprayDryerinBrazilunderCommissioning

http://www.niro.ru/images/spray-dryer-mobile.jpg

26

Figure of A typical spray Drying System

27

Drum-driers

Figure of Schematic drawing of Single, Double, Twin and Vacuum drum drier

28

What is pasteurizationUnit operation involving mild heat treatment of food, generally below

100°C

http://www.katiescowsandudderthings.com/morepainted.htmhttp://images.amazon.com/images/P/B0001B8WBC.01-A34S2NBKKS5E44._SCMZZZZZZZ_.jpg

http://www.unitedwaysb.org/Ice%20Cream.jpg

29

What is the purpose of pasteurization

• Extend the shelf-life of food for days to months

30

How does the pasteurization work?• By enzyme inactivation• By microbial destruction

Fellow, 1990

31

What is the most important factor in food which determines the severity of heat treatment in pasteurization

• pH of food

32

Equipment for pasteurization of liquid food

• Packaged liquid food: – Hot-water pasteurizer, tunnel pasteurizer– Beers, fruit juices

• Unpackaged liquid food:– Heat exchanger

33

What is HACCP?

-evaluation system used to ensure food safety by predicting and preventing risks during the processing of foods

-proactive concept ensuring food safety from harvest to consumption

34

-practically involves 7 principles:

(1)assessing hazards,

(2)identifying CCPs,

(3)setting up CCP control limits,

(4)monitoring CCPs,

(5)taking corrective action,

(6)verifying the system is working,

(7)setting up record-keeping system,

35

36

Biological, chemical and physical ‘hazards’Biological hazards• Pathogenic G- bacteria• Pathogenic G+ bacteria• Viruses• Parasites and protozoa• MycotoxinsChemical hazards• Cleaning chemicals• Pesticides, allergens• Toxic metals• Nitrites, nitrates and N-nitroso compounds• Polychlorinated biphenyls• Plasticizers and packaging migration• Veterinary residues• Chemical additivesPhysical hazards

37Key stages – maintaining the HACCP System

38

Major groups of packaging materials

• Shipping containers: protect and contain the contents during transportation and distribution

• Retail containers: protect content and advertise the food

39

Types of packaging materials

• Textiles and wood• Metal• Glass• Flexible films• Paper and board

40

Textile and wood

• Textile: grain, flour, sugar, salt• Wood: wines, spirits

41

Metal

• Total protection, ambient storage• Expensive materials, transportation cost• 2-piece can, 3-piece can

42

Glass

• Composition: sand, sodium oxide, calcium oxide, broken glass

43

Flexible films

• Single films vs laminated films• Single films

– Extrusion of melted pellets– Polyethylene, polypropylene

• Laminated films– Two or more films– Adhesive or dry bonding

44

Paper and board

• Paper– From wood chips

• Board– Wood chips but thicker

45

Current Food Laws in Hong Kongmainly in Chapter (CAP.) 132 of the Public Health and Municipal Services Ordinance

46

Schedule 3, Marking and Labelling of Prepackaged Foods

1. name or designation

2. list of ingredients3. list of ingredients of exempt food4. indication of minimum duration (best before vs use by)

5. statement of special conditions for storage or instructions for use

6. name and address of manufacturer or packer

7. count, weight or volume

8. appropriate language

47

Reference

• Fellow, P.J. 1990 or 2000. Food Processing Technology: Principles and Practice. Ellis Horwood

• http://www.fehd.gov.hk/safefood/food_safety_plan/library/7requirement.html

48

--END--