Nestlé Research Center EVITHERM WORK 2004 : FOOD A. RAEMY Nestlé Research Centre Nestec LTD CH- 1000 Lausanne 26 Switzerland According to the request of

Nestlé Research Center

EVITHERM WORK 2004 : FOOD

A. RAEMY

Nestlé Research Centre

Nestec LTD

CH- 1000 Lausanne 26

Switzerland

According to the request of Joachim Fischer, PTB, Berlin

Nestlé Research Center2004-01-15 NRC/FS - ARY2

Evitherm 2004: data main requirements (1)

Specific heats of foods and some non food materials (mainly packaging and process materials such as stainless steel, copper, polymers,…)

Glass transition temperatures which are abrupt changes in specific heats

Thermal conductivity

Basics of thermometry



Phase transition (melting,…) temperatures

Reaction (oxidation, Maillard,…) onset temperatures

Transition and reaction enthalpy values

Enthalpies normed at –60°C

Data in relation with process safety (self-ignition temperatures under specific conditions,…)



Information has to be presented as:

- tables - graphs - phase diagrams

Some formulas are necessary:

- Q = m c ΔT

- Fourier equation


Evitherm 2004: industrial associations in Europe

Caobisco, Brussels, Belgium ASIC, Paris, France Biscuit, Cake, Chocolate & Confectionery, London, UK ILSI (Int. Life Sciences Institute) Europe, Brussels,

Belgium Campden and Chorleywood Food Research

Association, Chipping Campden, UK Leatherhead Food International, Leatherhead, UK IVLV ( Industrievereinigung für Lebensmitteltechnologie

und Verpackung) Munich, Germany PIRA, Packaging Research, Leatherhead, UK


Evitherm 2004: trade publications

Commercial publications such as:

- Lebensmittel Technologie (CH)

- Der Lebensmittelbrief (GE)

- Lebensmittel-Industrie (CH)

Bulletins from INRA, ENSIA, Leatherhead, FSTA, Campden and Chorleywood

Scientific journals such as:

- J. of Food Engineering

- Science des Aliments


Evitherm 2004: contacts outside

Anita Mikkonen, VTT Biotekniikka, Finland

Philip Barlow, National University of Singapore, Singapore

Douglas Goff, University of Guelf, Canada

Lebert Grierson, The University of the West Indies, Trinidad and Tobago


Evitherm 2004: network of contacts

Michel Ollivon, CNRS Chatenay-Malabry, France

Perla Relkin, ENSIA, Massy, France

Yrjö Roos, University College Cork, Ireland

Alberto Schiraldi, DISTAM, Milan, Italy

Danièle Clausse, UT Compiègne, France

Bertrand Roduit, AKTS, Sierre, Switzerland


Evitherm 2004: food businesses

Coffee: Nestlé, Kraft, Procter and Gamble,…

Oil and fat: Unilever

Tea: Lipton, Nestlé

Dairy: Danone, Nestlé, Milupa

Fish: Findus

Additives, emulsifiers: Danisco,…


Evitherm 2004: special remarks

It is difficult to have scientific contacts with small food companies

To distribute thermal information in small companies, the best persons would be:

- Pierre Le Parlouër, Thermal Consulting, Caluire (F)

- dedicated small companies

- interested university professors

Nestlé Research Center

First approach: Specific heat (Cp) of foods

-Theoretical calculations- Experimental determination

- Literature


Evitherm 2004: Specific heat

General formula is: Q = m c T

[Q] = J or W s

[m] = g (or kg)

[c] = J / g °C (or J/kg °C)

T = °C or K



Theoretical calculation

Food composition has to be known.

Specific heat at ambient temperature of the food is obtained by proportional addition of the specific heat of each food constituent (water, carbohydrate, lipid, protein, ashes).


Evitherm-2004: Specific heat

Theoretical calculation

Specific heat of food constituents [1]

- For water: 4.18 J/g- For carbohydrate: 1.42 J/g- For lipid: 1.67 J/g (somewhat low)- For protein: 1.55 J/g- For ashes: 0.84 J/g- For ice: 2.11 J/g

[1] V. Gekkas, Transport phenomena of foods and biological materials, CRC Press, Boca Raton,1992.



Remarks

- Specific heats of solids increase with increasing temperatureV. Gekas gives the caracteristic parameters of a quadratic equation describing this effect

- Specific heat of water does practically not change between 0°C and 100°C

- Specific heat depends strongly on the water content of the considered product

- Some non-food specific heat values are also of interest (copper, stainless steel, aluminium,…).



Experimental determination

Calorimetric or DSC measurements allow to determine food specific heats at the temperature of interest.

Normally 3 measurements are necessary:

- Reference material, usually synthetic sapphire- Empty cell- Sample cell





Formula is:

01

02

2

112 QQ

QQ

m

mCC

where m1 is the mass of the standard substance, m2 is the sample mass, C1 is the

specific heat of the standard substance, and Q0, Q1 and Q2 are the required heat

quantities for the empty cell, the standard substance and the sample, respectively.

Remark: modern instrumentation has quicker methods but this is the most precise.



Remarks:

- Specific heat is generally determined at temperatures where the sample present no phase transitions

- Glass transition phenomena are sometimes presented in the specific heat determination

- Thermal conductivity is often found in the literature indicating specific heat.



Literature on specific heat of foods

[1] N. N. Mohsenin, Thermal properties of food and agricultural materials, Gordon and Breach, New York, 1980.

[2] M. Pyda, Conformational Contribution to the Heat Capacity of the Starch and Water System, J. of Polymer Science:Part B: Polymer Physics, 39 (2001) 3038-3054.

[3] A. Raemy and P. Lambelet, A calorimetric study of self-heating in coffee and chicory, J. Food Technology 17 (1982) 451-460.



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Nestlé Research Center EVITHERM WORK 2004 : FOOD A. RAEMY Nestlé Research Centre Nestec LTD CH- 1000 Lausanne 26 Switzerland According to the request of