Ignatiadis, P.

Silva, C. L. M.

English

Repositório Institucional da Universidade Católica Portuguesa

Process Optimisation andMinimal Processing of FoodsProceedings of the first main meetingEuropean CommissionCOPERNICUS PROGRAMMEConcerted action CIPA-CT94-0195EscolaSuperiordeBiotecnologia, Porto, Portugal, December 1995                    Editor : Jorge C. OliveiraProject Coordinator : Fernanda A. R. Oliveira            Area leader : Marc E. HendrickxVolume 1: Thermal ProcessingA critical literature search was carried out on i) instrumental methods to measure objectivelythe colour of foods and ii) the determination of the degradation kinetics of food colour underthermal processing conditions. Although there is a significant number of publications dealingwith colour measurement and the effect of thermal processing conditions on the colour change,the standardization of measuring methods and the kinetic models are included in only a few. Inthis communication, a critical review is presented and recommendations for further work aregiven.It is well known that the excessive heating of foods produces considerable losses in theorganoleptic quality of the final products (Hayakawa and Timbers, 1977).Kinetic models of the  thermal degradation of quality attributes are essential to design newprocesses that maximize final quality retention with the required degree of safety.Colour is an organoleptic property that greatly affects the consumer’s acceptability of mostfood products. Therefore, the retention of colour may be used as an indicator of the damage tothe quality of foods due to thermal processing (Banga et al, 1993).The objective measurement of food colour can be used for on-line quality control of foodprocesses. Although the sensory evaluation of food colour is more reliable, it is also a subjectiveand time consuming method (Ohlsson, 1980).The objective of this work was to perform a critical literature search on: 1) Instrumentalmethods to measure objectively the colour of food products, 2) Mathematical modeling of foodcolour degradation kinetics under thermal processing conditions and 3) Research work applyingcolour degradation kinetic data to optimize process conditions in terms of final quality retention.76Process Optimisation and Minimal Processing of Foods Process AssessmentSummaryModelling Food Colour Degradation Kinetics - A ReviewCristina L. M. Silva & Panos IgniatidisEscola Superior de Biotecnologia, Universidade Católica Portuguesa, Porto, Portugal1. IntroductionMost colours are uniquely specified by a set of three imaginary red (X), green (Y), and blue (Z)primaries. These are CIE tristimulus values. To make colour data more intuitive and easier tointerpret, these tristimulus values are usually converted to other colour scales (e.g. luminancefactor Y% and the chromaticity coordinates x, y). The Hunter L, a and b colour scales areopponent-type systems. These measure the degree of lightness (L), the degree of redness orgreenness (+/- a), and the degree of yellowness or blueness (+/- b) (Hutchings, 1994). Thedifference between two colors may be calculated as:(1)where TCD is the total colour difference.Some other more particular colour parameters have been used in the field of food science:e.g. browning index,(2)Yellowness index YI = 142.86 b / L                                                      (3)and the parameter S.S = R560 + R590 + R635                                                 (4)As can be observed in table 1, most of the work published in the field of modelling colourthermal degradation considered first order models:(5)or(6)C = Co 10- t / DTC = Co exp (- kT t)Bronwning index = absorbance ratio A520/ 430 or 420 nmTCD = ∆a2 + ∆b2 + ∆L277Silva & Igniatidis Thermal Processing2. Colour measurements3. Modelling colour changeswhere C is the parameter of color, Co the level of C at time zero, kT the rate constant atconstant temperature T, DT the decimal reduction time at temperature T and t the time.Zero order models have also been widely used (Table 1): (7)The reaction order can be determined using the following equation:(8)where n is the reaction order.The effect of temperature on reaction rate constants was described by the Arrheniusequation:(9)where Ea is the activation energy, T the absolute temperature, R the universal gas constantand ko the rate constant at infinite temperature.For the thermal destruction time model described in equation 6, the temperaturedependence follows the equation proposed by Bigelow:(10)where z is the temperature sensitivity of the decimal reduction time DT.Table 1 presents a review of the research work published on modelling colour thermaldegradation kinetics. Several products were studied and several instruments and colour parameters were used toquantify the colour. For the same type of product there are no standardized methods.In most cases a first order or a zero order model was able to model the reaction kinetics atconstant temperature. The Arrhenius (9) or the Bigelow (10) equations were used to describe theeffect of temperature.The number of papers relating the objective measurement of food colour with sensoryevaluation is still limited. Furthermore, very few authors use the kinetic  data determined tovalidate and/or optimize processing conditions in terms of final quality retention.DT = DTref 10(Tref - T) / zkT = ko exp (- EaR T)ln ( - ∂C∂t ) = ln kT + n ln CC = Co - kT t78Process Optimisation and Minimal Processing of Foods Process Assessment4. Results reported in literature79Silva & Igniatidis Thermal ProcessingTable IKinetics of color degradationReference Product TemperatureRange (˚C)Equipment ColorParameterKinetics D121˚C(min)Z(˚C)k121˚C  (min -1)ko(sec-1)Ea(kJ/mol)ProcessAssessmentHayakawa &Timbers (1977)asparagusgreen beansgreen peas79.5 - 149 Gardner AC-1 - a/b  1st order1st order1st  order17212541.738.939.4------------------------------------NoOhlsson (1980)fish puddingliver pastestrained beefstrainedveget.tomato saucevanilla sauce110 - 134 Hunterlab colorL 1st order1st order1st order1st order1st order1st order------------------------252122212820------------------------------------------------------------------------NoRao et.al.(1981)peas 98.9 - 126.7 Hunter D25-3 a/b 1st order 13.2 38.3 ---- ---- 73.15 NoMerin et.al.(1987)prickly pear -fruit50 - 90 SpectrophotometerAbsorvance at 535nm1st order 523.6 74.3 ---- ---- ---- NoRhim et.al.(1988)skim milk 100 - 150 Spectrogardcolor systemLabCbrowningindex1st orderorder 0order 02nd orderorder 0------------------------------------------------------------1.95 x10113.75 x10112.75 x10123.17 x1092.65 x1012114.8104.9110.3103.6123.5NoRhim et.al.(1989)grape juice 60 - 95 Spectrogardcolor systemLaTCD1st order1st orderorder 0------------------------------------1.30 x10128.95 x10144.80 x1010114.75131.8092.81NoPagliarimiet.al. (1990)milk 70 - 140 ColorimeterMinoltaTCDYIorder 0order 0------------------------2.50 x10119.58 x1011101.8117.5NoSanchez et.al.(1991)picked greenolives70 - 90 Spectrophoto-meterS 1st order 523.6 74.3 ---- ---- ___ YesGhazala et.al.(1991)modelsystemscolor / DDWcolor / MIX110 - 150 Minolta CT-210Y%xyY%xy1st order1st order1st order1st order1st order1st order24553525475520294360425230.237.837.238.137.037.70.0009630.0006680.0004940.0011600.0005400.000552------------------------102.381.483.181.083.482.1YesSeveral instruments and colour parameters are used to quantify the colour change duringthermal processing. For the same type of product there are no standardized methods. Few authors attempted to quantify the kinetics of colour degradation of foods under thermalprocessing conditions. In most cases where it is,  first or  zero order reaction kinetics are used.The work relating the objective measurement of food colour with sensory evaluation is stilllimited. Furthermore, very few authors use the kinetic data determined to validate and/oroptimize processing conditions in terms of final quality retention.There is a need to define adequate and standardized methods to measure objectively thecolour of food products.The kinetic data should be correlated with sensory evaluation.The use of colour kinetic data to assess the final product quality retention and predict optimalprocessing conditions must be evaluated.Banga, J. R., Alonso, A. A., Gallardo, J. M. & Pérez-Martin, R. I. (1993). Kinetics of ThermalDegradation of Thiamine and Surface Colour in Canned Tuna. Lebensmittel-Untersuchung un-Forschung 197, 127-131.Ghazala, S., Ramaswamy, H. S., van de Voort, F. R. & Al-Kanani, T. (1991). Kinetics of ClorDevelopement in Aqueous Systems at High Temperatures. Journal of Food Engineering 13, 79-89.Hayakawa, K & Timbers, G. E. (1977). Influence of Heat Treatment on the Quality of Vegetables:Changes in Visual Green Color. Journal of Food Science 42 (3), 778-781.Hutchings, J. B. (1994). Food Colour and Appearance. Blackie Academic & Professional, London.Merin, U., Gagel, S., Popel, G., Bernstein, S. & Rosenthal, I. (1987). Thermal Degradation Kineticsof Prichly-Pear-Fruit Red Pigment. Journal of Food Science 52 (2), 485-486.Ohlsson, T. (1980). Temperature Dependence of Sensory Quality Changes during ThermalProcessing. Journal of Food Science 45, 836-839.Pagliarini, E., Vernile M. & Peri, C. (1990). Kinetic Study on Color Changes in Milk Due to Heat.Journal of Food Science 55 (6), 1766-1767.Rao, M. A., Lee, C. Y., Katz, J. & Cooley, H. J. (1981). A Kinetic Study of the Loss of Vitamin C,Color, ans Firmness during Thermal Processing of Canned Peas. Journal of Food Science 46, 636-637.80Process Optimisation and Minimal Processing of Foods Process Assessment5. Conclusions6. Recommendations for further workReferencesRhim, J. W., Jones, V. A. & Swartzel, K. R. (1988). Kinetics Studies in the Colour Changes of SkimMilk. Lebensm.-Wiss. u.-Technol. 21, 334-338.Rhim, J. W., Nunes, R. V., Jones, V. A. & Swartzel, K. R. (1989). Kinetics of Color Change of GrapeJuice Generated using Linearly Increasing Temperature. Journal of Food Science 54 (3), 776-777.Sánchez, A. H., Rejano, L. & Montano, A. (1991). Kinetics of the Destruction by Heat or Colour andTexture of Pickled Green Olives. Journal of Science Food Agricultural 54, 379-385.Shin, S. and Bhowmik, S.R. (1995). Thermal Kinetics of Color Changes in Pea Puree. Journal ofFood Engineering 24, 77-86.81Silva & Igniatidis Thermal Processing

Modelling food colour degradation kinetics - A review

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Modelling food colour degradation kinetics - A review

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