KINETICS OF PIGMENT DEGRADATION IN SLICED COOKED HAM ELISANGELA c. MATTOS, CACIANO P.Z. NORERA and ADRIAN0 BRANDELLI' Instituto & CiEncia e Tecnologia de Alimentos Universidade Federal do Rio Grande do Sul 91501-970 Port0 Alegre. Brasil Accepted for Publication May 15, 2003 ABSTRACT Sliced cooked ham was vacuum packaged and held in the dark at -1SC. IOC, and 30C, and at IOC in the light, for up to 96 h. At 24 h intervals, samples were analyzed for pigment concentration by spectrophotometry . A decrease in pigment concentration was observed over time under all conditions. Pigment degradation increased at higher temperatwes and with light exposure. Kineticparameters were determined, indicating thatpigment degradation follows jirst order kinetics and the temperature dependence of these reactions indicated an Arrhenius relationship. The activation energy was 3.3 kcal/mol. The visible spectra for the extracted pigments in cooked ham showed the typical pattern of nitrosylmyoglobin. Pigments extracted from ham displayed in the light had spectra with similar absorption muxima to those from those stored in the dark. INTRODUCTION Color is an essential sensory property of foods, being a fundamental factor for customer acceptance. Food pigments are often modified by processing and/or storage, however, undesirable chemical or biochemical modifications must be avoided or minimized. The main modifications of myoglobin (Mb) during processing involve the oxidationheduction of iron andlor globin denaturation. When the globin molecule is denatured, myoglobin loses the capacity to bind oxygen, the tendency for iron to oxidize to the ferric state increases, and the iron-nitric oxide interaction is stronger. Such conditions enhance the stability of nitrosohemo- chrome of cured meats (van Elbe 1986). ' Corresponding author: ICTA-UFRGS, Av. Bento Goncalves 9500, 91501-970 Porto Alepe, Brasil. EMAIL: [email protected]Journal of Muscle Foods 14 (2003) 221-231. All Rights Reserved. 'Copyright 2003 by Food dr Nutrition Press, Inc., Trimbull, Connecticut. 22 1
Transcript
KINETICS OF PIGMENT DEGRADATION IN SLICED COOKED HAM
ELISANGELA c. MATTOS, CACIANO P.Z. NORERA and ADRIAN0 BRANDELLI'
Instituto & CiEncia e Tecnologia de Alimentos Universidade Federal do Rio Grande do Sul
91501-970 Port0 Alegre. Brasil
Accepted for Publication May 15, 2003
ABSTRACT
Sliced cooked ham was vacuum packaged and held in the dark at -1SC. IOC, and 30C, and at IOC in the light, for up to 96 h. At 24 h intervals, samples were analyzed for pigment concentration by spectrophotometry . A decrease in pigment concentration was observed over time under all conditions. Pigment degradation increased at higher temperatwes and with light exposure. Kinetic parameters were determined, indicating that pigment degradation follows jirst order kinetics and the temperature dependence of these reactions indicated an Arrhenius relationship. The activation energy was 3.3 kcal/mol. The visible spectra for the extracted pigments in cooked ham showed the typical pattern of nitrosylmyoglobin. Pigments extracted from ham displayed in the light had spectra with similar absorption muxima to those from those stored in the dark.
INTRODUCTION
Color is an essential sensory property of foods, being a fundamental factor for customer acceptance. Food pigments are often modified by processing and/or storage, however, undesirable chemical or biochemical modifications must be avoided or minimized.
The main modifications of myoglobin (Mb) during processing involve the oxidationheduction of iron andlor globin denaturation. When the globin molecule is denatured, myoglobin loses the capacity to bind oxygen, the tendency for iron to oxidize to the ferric state increases, and the iron-nitric oxide interaction is stronger. Such conditions enhance the stability of nitrosohemo- chrome of cured meats (van Elbe 1986).
' Corresponding author: ICTA-UFRGS, Av. Bento Goncalves 9500, 91501-970 Porto Alepe, Brasil. EMAIL: [email protected]
Journal of Muscle Foods 14 (2003) 221-231. All Rights Reserved. 'Copyright 2003 by Food dr Nutrition Press, Inc., Trimbull, Connecticut. 22 1
222 E.C. MA'ITOS, C.P.Z. NORERA and A. BRANDELLI
The n o d color of cured meats depends on pigment concentration in tissues, the degree of pigment conversion and the state of proteins. In cooked ham, pigment concentration is reduced and proteins are denatured, resulting in higher light reflection and consequently a pale pink color (Bard and Townsend 1971). Nitrite is a key ingredient in fixing the characteristic pink color of cured- meats. Model studies suggest that NO, generated through the reaction of nitrite with reductants, reacts with metMb to form metMbNO which subsequently accepts an electron from a reductant to form MbNO (Nakamura and Nakamura 1996). The cooked cured meat pigment has been shown to be a mononitrosyl ferrohemochrome (Killday et al. 1988).
In order to predict the extent of high quality shelf-life, and to be able to put a shelf-life on a product, knowledge of the rate of deterioration as a function of environmental conditions is necessary. To avoid studying each food component and each mode of deterioration at several temperatures for several time intervals. kinetic models which describe destruction rates must be determined. Given a certain rate of loss, if it is constant, the amount of change can be predicted by using mathematical models (Labua 1982; Lenz and Lund 1980; van Boekel 1996).
Some studies have developed degradation kinetics for pigments. Most research has been developed in model systems of green vegetables to determine the kinetic parameters of chlorophyll degradation (Steet and Tong 1996; van Boekel 2000). The deterioration constant for color loss of &carotene in the presence of oxygen, studied in a model system that simulate a dehydrated food, follows a first order kinetic (Teixeira-Net0 e? al. 1981). Color degradation of fresh meat follows first order kinetics with activation energy (Ea) ranging 44 to 101 kcal/mol (Adams and Huffman 1972; MacDougall and Taylor 1975).
The market for sliced cooked meats has been extremely dynamic in recent years. This market has increased by volume and by value, such that sliced ham accounts for more than 50% of sales (Economist Intelligence Unit 1996). However, this product exhibits a reduced shelf-life since it is susceptible to deterioration. Since color is a key factor to market success, and serves as indicative of product quality, it is relevant to investigate the determinant factors for color alterations in sliced ham. The aim of this work was to verify the kinetics of pigment loss in sliced m k e d ham stored at different temperatures and light exposition.
PIGMENT LOSS IN SLICED COOKED HAM 223
MATERIALS AND METHODS
Samples
Cooked ham with 2-3 days freshness was obtained from stores in Santa Rosa and Port0 Alegre (Brazil). Label ingredients included NaC1, glucose, sodium nitrite, sodium tripolyphosphate, and sodium erythorbate. Samples from three different lots were sliced (1 mm thickness), vacuum-packed and stored at -15C, 1OC or 30C until analyzed. Packaging material was 0.03 mm thick polypropylene bags with an oxygen permeability < 100 cm3 0, rn-, day-' am-' at 23C.
Storage Conditions
Sliced ham was stored in the dark at different temperatures (-15C, lOC, 30C), and at 1OC under illumination with cool white fluorescent light (2500 lux), for up to 4 days (96 h). At each 24 h time interval, a sample was removed and subjected to pigment extraction. Separate package was used for each removal time.
Determination of Pigment Concentration
Pigment concentration was determined as described by Hornsey (1956). Samples (10 g) were placed in flasks containing 40 mL acetone, 2 mL distilled water and 1 mL chloridric acid. The mixture was kept in the dark for 60 min and then filtered through Whatman No. 1 filter paper. The optical density was determined at 640 nm. Total pigments were expressed in ppm.
Spectral Analysis
Absorption spectra of acetone:water ham extracts were recorded in the visible range using a Pharmacia Ultraspec 3100 spectrophotometer (Amersham Pharmacia, Uppsala, Sweden) with 10 mm pathlength quartz cuvettes.
Data Processing
To determine the values of constant reaction, a first order model was used (Labuza 1982):
C - = exp[-kt] co
224 E.C. MATTOS. C.P.Z. NORERA and A. BRANDELLI
Where, k and (day-’) is the rate of reaction, C (ppm) is the pigment concentra- tion at time t, C, is the initial concentration of pigment.
Ql0 values were determined using the following equation:
Where: t, oc is the shelf-life at temperature T, and t, + loc is the shelf-life at temperature T + 1OC.
The data were analyzed using the Statistics Analysis System 6.0 software (SAS Institute 1993).
RESULTS AND DISCUSSION
Experimental values for pigment concentration at different temperatures are shown in Fig. 1. Pigment concentration decreased from about 57 ppm to about 40 ppm during the incubation time. Chen and Jones (1988) also observed a decrease in pigment concentration in vacuum-packed ham stored at 5C. This fading of cured meat color would be expected and is affected by packaging conditions, oxygen level, bacterial growth, lipid oxidation and light (Wilson 198 1 ; Bello-Gutierrez and Villanova-Rub 1982). Greater decrease of pigment concentration was observed at higher temperatures (Fig. 1). Color loss of heme pigments is often associated with oxidative processes, stimulated by light and increasing temperature (Faustman and Cassens 1990). In this case, we assume the effect of temperature was observed in the presence of oxygen, because no absolute vacuum can be achieved and packaging is not an absolute barrier against gas diffusion. Oxygen permeability of polypropylene increases with temperature, showing good agreement with the Arrhenius equation (Gajdos e~ al. 2001). In addition, the cured meat pigments nitrosylmyoglobin and nitrosylhemochrome are unstable and, in the presence of oxygen or by the action of peroxides, oxidize to brown, grey and green pigments. Some lactobacilli present in cured meats produce hydrogen peroxide which, if not broken down, can oxidize the pigments and give rise to discoloration (Kotzekidou and Bloukas 1996).
PIGMENT LOSS IN SLICED COOKED HAM 225
6o 1 h
k n - 50 E
I= 40
C 0 .- CI
.Id
K 8 8 c C
E m ’ 30
0 2 3 4 5
Time (days)
FIG. 1 . EXPERIMENTAL VALUES FOR PIGMENT CONCENTRATION AND PREDICTED CURVES FOR SLICED HAM INCUBATED AT DIFFERENT TEMPERATURES
(9) -15C, (m) 1OC. ( A ) 30C.
Degradation of pigments in sliced cooked ham followed a first order reaction, as indicated by the linearity of the normalized data on plots (Fig. 1). This data is consistent with that reported for pigment degradation in meat foods (Adams and Huffman 1972; MacDougall and Taylor 1975). Reaction rate constants (k) were determined from the slopes of normalized curves (Table 1). The fi values from linear regression performed on each replicate were always > 0.9.
When the tests were conducted with light exposure at lOC, the decrease of pigment concentration was higher than when dark stored (Fig. 2 and Table 1). Discoloration of vacuum-packed ham is normally encountered as a result of photooxidation of pigments during the first 24 h of display in illuminated cabinets (Andersen ef al. 1990).
226 E.C. MATTOS, C.P.Z. NORERA and A. BRANDELLI
TABLE 1 . REACTION CONSTANTS FOR PIGMENT DEGRADATION IN SLICED COOKED HAM
-15c
1oc
30C
1OC (light exposed)
57.00
57.27
56.38
56.90
0.051
0.070
0.120
0.100
- 60 Ea n c 0
Y
.- CI 2 50 C C
c 8 8 ’E 40
ii E m
30 I I I I I I
0 1 2 3 4 5
Time (days)
FIG. 2. EXPERIMENTAL VALUES FOR PIGMENT CONCENTRATION AND PREDICTED CURVES FOR SLICED HAM INCUBATED AT 1OC IN THE DARK (*) OR UNDER
LIGHT EXPOSURE (.)
PIGMENT LOSS IN SLICED COOKED HAM 221
The shelf-life of the product was simulated at different temperatures considering that its acceptability, based on sensory evaluation, occurs when the product reaches 22% color loss. This can be observed in Fig. 3, where the shelf-life decreases as the temperature increases. The Ql0 value was determined from equation 1.2; this result indicates that temperature has a moderate effect on pigment loss. This fact agrees with previously observed reports that heme pigment degradation results from the combined effects of temperature, light and oxygen. Although light and oxygen are often implicated as the major factors affecting pigment stability, temperature, relative humidity, and pH also influence the color of fresh pork (Zhu and Brewer 1998) and cured ham (Mandigo and Kunert 1973; Wilson 1981).
The Arrhenius plot for pigment degradation was determined (Fig. 4). The linearity of the data indicate that the rate constants as a function of temperature all followed the Arrhenius relationship. Linear regression was performed on the Arrhenius plot determining that the activation energy (Ea) was 3.3 kcal/mol (I2 = 0.97), indicating a weak temperature dependence for discoloration in sliced ham. Some authors (Labuza er al. 1982; Bergquist and Labuza 1983) suggest
0 Temperature ( C)
FIG. 3. SHELF-LIFE PLOT FOR SLICED HAM WITH COLOR LOSS LIMITATION FIXED AS 22%
228 E.C. MATl'OS. C.P.Z. NORERA and A. BRANDELLI
0,lO
0,Ol
0,0032 0,0034 0.0036 0,0038 0,0040
lfr (l/K)
FIG. 4. ARRHENIUS PLOT FOR THERMAL DEGRADATION OF SLICED HAM
that it is frequently possible to obtain Ea values with a satisfactory determination coefficient (3 > 0.95) from three temperatures. The Ea was lower than those observed for fresh meat (Adams and Huffman 1972; MacDougall and Taylor 1975), agreeing with the fact that cured meat pigments are often more stable than fresh meat pigments (van Elbe 1986), and its deterioration rate is less influenced by temperature.
Absorption characteristics of the cooked cured-meat pigments were compared to those of pigments extracted from ham after different storage conditions (Fig. 5). The visible spectra for the acetone-extracted pigment in cooked ham showed maxima at 395, 475, 535 and 565 nm, typical pattern of nitrosylmyoglobin (Sakata and Nagata 1983; Millar m al. 1996). After pigments were dissolvdextracted into acetone:water mixtures as described by Homey (1956), similar maxima were apparent in all cases. Furthermore, pigments extracted from ham stored under light had spectra with similar absorption maxima to those from dark storage.
PIGMENT LOSS IN SLICED COOKED HAM 229
1,O r I 0,25
0,20
0,15
0,lO
0,05
360 380 400 420 440 450 500 550 600 650
Wavelength (nrn) Wavelength (nrn)
FIG. 5. ABSORPTION SPECTRA OF HEME PIGMENTS EXTRACTED WITH ACETONWATER ( - ), AFTER STORAGE AT 1OC UNDER
DARK ( ---- ) OR LIGHT EXPOSITION ( - - )
REFERENCES
ADAMS, J.R. and HUFFMAN, D.L. 1972. Effect ofcontrolled gas atmosphere and temperatures on quality of packaged pork. J. Food Sci. 37, 869-872.
ANDERSEN, H.J., BERTELSEN, G., OHLEN, A. and SKIBSTED, L.H. 1990. Modified packaging as protection against photodegradation of the colour of pasteurized, sliced ham. Meat Sci. 28, 77-83.
BARD, J. and TOWNSEND, W.E. 1971. Meat curing. In Science of Meat and Meat Products, (J.F. Price and B. Schweigert. eds.) pp. 328-348, Freeman, London.
BELLO-GUTIERREZ, J. and VILLANOVA-RUIZ, R.G. 1982. Formation and stability of colour of meat products. Anal. Bromatol. 33, 59-68.
BERGQUIST, S. and LABUZA, T.R. 1983. Kinetics of peroxide formation in potato chips undergoing a sine wave temperature fluctuation. J. Food Sci. 43, 712.
230 E.C. MAITOS. C.P.Z. NORERA and A. BRANDELLI
CHEN, C.M. and JONES, K.W. 1988. Chemical, sensory and microbiological properties of cured pork and turkey ham products. J. Food Sci. 53,
Economist Intelligence Unit. 1996. Market survey 2. Sliced cooked meats. Retails Business Market Surveys 456, 23-45.
FAUSTMAN, C. and CASSENS, R.G. 1990. The biochemical basis of discoloration in fresh meat: a review. J. MuscIe Foods I, 217-243.
GAJDOS, J., GALIC, K., KURTANJEK, Z. and CIKOVIC, N. 2001. Gas permeability and DSC characteristics of polymers used in food packaging. Polymer Testing 20, 49-57.
HORNSEY, H.C. 1956. The colour of cooked cured pork. I. Estimation of nitric oxide-heme pigments. J. Sci. Food Agric. 7, 534-540.
KILLDAY, K.B., TEMPESTA, M.S., BAILEY, M.E. and METRAL, C.J. 1988. Structural characterization of nitrosylhemochromogen of cooked cured meat: implications in the meat-curing reaction. J. Agric. Food Chem. 36, 969-975.
KOTZEKIDOU, P. and BLOUKAS, J.G. 1996. Effect of protective cultures and packaging film permeability on shelf-life of sliced vacuum-packed cooked ham. Meat Sci. 42, 333-345.
LABUZA, T.P. 1982. She&life Dating of Foods. Food & Nutrition Press, Trumbull, CT.
LABUZA, T.P., BAHNSACK, K. and KIM, M.W. 1982. Kinetics of protein quality loss stored under constant and square wave temperature distribu- tions. Cereal Chem. 59, 142-145.
LENZ, M.K. and LUND, D.B. 1980. Experimental procedures for determining destruction kinetics of food components. Food Technol. 34, 51-55.
MACDOUGALL, P.B. and TAYLOR, A.A. 1975. Color retention in fresh meat stored in oxygen - A commercial scale trial. J. Food Technol. 10.
MANDIGO, R.W. and KUNERT, G.F. 1973. Accelerated pork processing: cured color stability of hams. J. Food Sci. 38, 1078-1079.
MILLAR, S.J., MOSS, B.W. and STEVENSON, M.H. 1996. Some observa- tions on the absorption spectra of various myoglobin derivatives found in meat. Meat Sci. 42, 277-288.
NAKAMURA, M. and NAKAMURA, S. 1996. Conversion of metmyoglobin to NO myoglobin in the presence of nitrite and reductants. Biochim. Biophys. Acta 1289, 329-335.
SAKATA, R. and NAGATA, Y. 1983. A method for measuring the color forming ability of processed meat products: extractability of the native nitroso hem pigments. Jpn. J. Zootechnol. Sci. 54, 667-670.
SAS Institute. 1993. STAT Guide for Personal Computers. Statistical Analysis System Institute, Cary, NC.
1273- 1277.
339-341.
PIGMENT LOSS IN SLICED COOKED HAM 231
STEET, J.A. and TONG, C.H. 1996. Degradation kinetics of green color and chlorophylls in peas by colorimetry and HPLC. J. Food Sci. 61,924-927.
Oxygen uptake and /3-carotene decoloration in a dehydrated food model. J. Food Sci. 46, 665-669.
VAN BOEKEL, M.A.J.S. 1996. Statistical aspects of kinetic modeling for food science problems. J. Food Sci. 61, 477-485.
VAN BOEKEL, M.A.J.S. 2000. Kinetic modelling in food science: a case study on chlorophyll degradation in olives. J. Sci. Food Agric. 80, 3-9.
VAN ELBE, J.H. 1986. Chemical changes in plant and animal pigments during food processing. In Role of Chemistry in the Quality of Processed Food, (O.R. Fennema, W.H. Chang and C.Y. Lii) pp. 41-63, Food & Nutrition Press, Trumbull, CT.
