Journal of Food Engineering 66 (2005) 259–265 www.elsevier.com/locate/jfoodeng Effect of thermal processing on the quality loss of pineapple juice Marisa Rattanathanalerk, Naphaporn Chiewchan *, Walaiporn Srichumpoung Department of Food Engineering, King Mongkut’s University of Technology Thonburi, Tungkru, Bangkok 10140, Thailand Received 24 November 2003; accepted 14 March 2004 Abstract Three indexes, namely colorimetric Hunter parameters (L, a, b and DE), hydroxymethylfurfural (HMF) and brown pigment formation, were monitored to determine the quality loss of pineapple juice at temperatures ranging from 55 to 95 °C The changes in a and b values followed first order kinetics while DE fitted well to a combined model which described both non-enzymatic browning reaction and destruction of carotenoid pigment For browning indexes, HMF and brown pigment formation increased linearly with heating time and could be explained using zero order reaction kinetics The results suggested that processing temperature had a significant effect on the color change of pineapple juice The dependence of the rate constant on temperature was represented by an Arrhenius equation Ó 2004 Elsevier Ltd All rights reserved Keywords: Color change; Hydroxymethylfurfural; Kinetics; Non-enzymatic browning; Pineapple juice Introduction Pineapple (Ananas cosmosus) is one of the most important commercial fruits of Thailand The fruit can be consumed fresh or processed in various forms and pineapple juice is a popular product due to its very pleasant aroma and flavor Thermal treatment is generally applied to extend shelf life of fruit products However, heating processes can affect the quality of product which leads to consumer dissatisfaction Non-enzymatic browning reactions and pigment destruction have been found to be major causes of such problems Therefore, kinetic studies are required and used to predict quality degradation resulting from process conditions Different methods can be used to determine the extent of color change Color measurement is simple and faster than chemical analysis The Hunter parameters (L, a, and b) have been proven to be useful for describing visual color change of various fruit products (Avila & Silva, 1999; Garza, Ibarz, Pag an, & Giner, 1999; Ibarz, Pagan, & Garza, 1999) The L value represents the light–dark spectrum, a value is for the green–red spectrum and b * Corresponding author Fax: +66-2470-9240 E-mail address: naphaporn.rat@kmutt.ac.th (N Chiewchan) 0260-8774/$ - see front matter Ó 2004 Elsevier Ltd All rights reserved doi:10.1016/j.jfoodeng.2004.03.016 value represents the blue–yellow spectrum (Ranganna, 1986) Other assays include the analysis of intermediates and final products of non-enzymatic browning reactions The measurement of 5-hydroxymethylfurfural (HMF), an important intermediate, is widely used as an indicator of Maillard reactions, i.e browning development (Bozkurt, Gogus, & Eren, 1999; Cohen, Birk, Mannheim, & Saguy, 1998; Garza et al., 1999) Kinetic models have been developed to evaluate color degradation and non-enzymatic browning reactions during processing of fruit products such as apple juice (Cohen et al., 1998), pear puree (Ibarz et al., 1999) and peach puree (Garza et al., 1999) For pineapple products, Fontana, Howard, Criddle, Hansen, and Wilhelmsen (1993) studied the effects of additional components, i.e sugars, organic acids, on the quality deterioration kinetics of pineapple concentrate at 60–80 °C However, information regarding the changes in quality of pineapple drinks in terms of color change and non-enzymatic browning during heating is unavailable This work was aimed at investigating the quality loss of pineapple juice as affected by heat treatment Visual color, 5-hydroxymethylfurfural (HMF) and brown pigment accumulation were monitored during heating at 55–95 °C The kinetics of these indicators were also investigated The information obtained from the study 260 M Rattanathanalerk et al / Journal of Food Engineering 66 (2005) 259–265 could be used as a guideline for designing thermal processes to reduce the quality degradation of the products measured and total color differences were calculated from L, a and b values Material and methods 2.4 Determination of non-enzymatic browning index and 5-hydroxymethylfurfural (HMF) 2.1 Preparation of pineapple juice Fresh Smooth Cayenne pineapples were obtained from a local market After rinsing the fruit in tap water, the shell and core were removed using a stainless steel knife The flesh was cut into small pieces and the juice was extracted using a hydraulic machine (Sakaya Model 4104, Thailand) to extract the juice Total soluble solid (TSS) and pH value of the juice were determined in the ranges of 12.2–14.2° Brix and 3.74–4.00, respectively The prepared juice was then kept at °C until used 2.2 Thermal treatment A series of thin wall glass tubes (length 30 cm; inner diameter mm; wall thickness mm) were filled with ml of pineapple juice The tubes (filled with the juice) were sealed at both ends and then subjected to heat in a water bath (Memmert Model W 600, Denmark) at 55, 65, 75, 85 and 95 °C for 80 The come up times for every condition was less than The temperature of the juice at the center of a tube was monitored during the experiments using type T thermocouples to an accuracy of ±1 °C The tubes were removed every 10 and immediately cooled in an ice-water bath in order to stop the heat accumulation The control experiments (without heat treatment) were done by the same procedure, filling ml of pineapple juice into the tubes and placing them directly in the ice-water bath Color change, non-enzymatic browning index and hydroxymethylfurfural (HMF) of pineapple juice were determined using a spectrocolorimeter (JUKI Model JP7100/C, Japan) and spectrophotometer (Shimadzu Model UV-2101 PC, Japan), respectively All experiments were performed in three replicates The following assays were performed using the methods as mentioned in Cohen et al (1998) ml of 95% ethyl alcohol was added to ml of pineapple juice sample The mixture was centrifuged at 1000g for 15 The supernatant of the centrifuged sample was separated into two portions One was taken to measure the absorbency at 420 nm for the non-enzymatic browning index To determine the HMF content, ml of the other portion was introduced into a 16 ml screw cap tube ml of 12% w/w trichloroacetic acid (TCA; Sigma, Germany) and ml of 0.025 M thiobabituric acid (TBA; Carlo Erba, Italy) were subsequently added and mixed thoroughly The tubes with sample were then placed in the water bath (Memmert Model W 600, Denmark) at 40 °C (±0.5 °C) After incubating for 50 min, the tubes were cooled immediately using tap water and the absorbency was measured at 443 nm A calibration curve of HMF (Aldrich, Germany) was utilized to quantify the HMF concentration 2.5 Experimental design The experiments were conducted for five levels of temperatures (55, 65, 75, 85 and 95 °C) A 2-factor factorial design was used in scheduling of the experiments with three replicates in each case 2.6 Data analysis The results were reported as an average of three replicates Analysis of variance (ANOVA) of the two factors and interactions were applied to the different sets of data with a significant level of 0.05 (a ¼ 0:05) Results and discussion 2.3 Color measurement 3.1 Color change of pineapple juice during heat treatment Color changes of pineapple juice were analyzed by measuring the transmittance using a spectrocolorimeter 2° North skylight was used as the light source The spectrocolorimeter was calibrated against distilled water (L ¼ 100, a ¼ 0, b ¼ 0) before the measurement (according to the equipment instruction manual) A glass cuvette (3.5 · · 1.5 cm3 ) containing heat-treated juice was placed in the cell transmittance specimen compartment The lid of the compartment was closed and the analysis was then conducted Three Hunter parameters, namely ‘‘L’’ (lightness), ‘‘a’’ (redness and greenness) and ‘‘b’’ (yellowness and blueness) were The color degradation of pineapple juice as affected by thermal processing was investigated using Hunter parameters (L, a and b) The enzymatic browning reaction was neglected in this study as the enzymes causing browning were susceptible to heat, at temperatures of >50° (Martinez & Whitaker, 1995) Therefore, nonenzymatic browning and pigment destruction were considered as the major causes of color change in pineapple juice The results obtained were presented in terms of L=L0 , a=a0 and b=b0 when L0 , a0 and b0 represented the initial M Rattanathanalerk et al / Journal of Food Engineering 66 (2005) 259–265 4.50 4.00 3.50 3.00 2.50 ∆E values once the sample temperature had reached the set temperature The plots between relative Hunter parameters and processing time at different temperatures are shown in Figs 1–4 In order to explain the phenomena of color change in pineapple juice, the data 261 2.00 1.50 1.00 1.04 0.50 1.02 0.00 1.00 L/L0 10 20 30 40 50 60 70 80 90 Heating time (min) 0.98 0.96 Fig The change of total color different (DE) of pineapple juice samples at different heating temperatures: 55 °C ðrÞ, 65 °C (h), 75 °C (m), 85 °C (s) and 95 °C (d) 0.94 0.92 0.90 0.88 0.86 0.84 10 20 30 40 50 60 70 80 90 Heating time (min) Fig The change of lightness ðL=L0 Þ of pineapple juice samples at different heating temperatures: 55 °C ðrÞ, 65 °C (h), 75 °C (m), 85 °C (s) and 95 °C (d) 1.25 a/ao 1.20 1.15 1.10 1.05 1.00 10 20 30 40 50 60 Heating time (min) 70 80 90 Fig The change of redness ða=a0 Þ of pineapple juice samples at different heating temperatures: 55 °C ðrÞ, 65 °C (h), 75 °C (m), 85 °C (s) and 95 °C (d) 1.00 b/bo 0.96 0.92 0.88 0.84 0.80 10 20 30 40 50 60 70 80 Heating time (min) Fig The change of yellowness ðb=b0 Þ of pineapple juice samples at different heating temperatures: 55 °C ðrÞ, 65 °C (h), 75 °C (m), 85 °C (s) and 95 °C (d) were fitted using a kinetic model and kinetic rate constants are presented in Table Fig shows the change in relative L values during heat treatment under various conditions With increasing temperature and time, pineapple juice became darker which corresponded to a decrease in L value Most of the previous works demonstrated that the changes in L value as affected by heat treatment followed first order kinetics (Avila & Silva, 1999; Garza et al., 1999; Ibarz et al., 1999) Moreover, two consecutive first order reactions have been proposed when the experimental data could not be described by single reaction (Barreiro, Milano, & Sandoval, 1997) However, it was obvious that the changes in L value found in the present study could not be fitted to any simple kinetic model The degradation in L value might be influenced by an increase in a value and a decrease in b value The results suggested that the reduction in the luminosity were not from a single mechanism Therefore, the kinetics for describing L value was not determined The evolution of an a parameter with treatment time can be fitted to both zero and first order reactions (Fig 2) However, with increasing temperature, the experimental data were better fitted to first order kinetics This finding was consistent with many previous studies (Avila & Silva, 1999; Garza et al., 1999; Ibarz et al., 1999) The values of the kinetic constants increased with treatment temperature This supported the theory that an increase in heating temperature induced the color shift to red Since the major color of pineapple juice is yellow, the amount of this pigment in pineapple flesh is an excellent measure of quality (Mehrlich & Felton, 1980) In this study, the b value was used as an indicator to describe the pigment destruction in the juice Fig shows that the first order kinetic model fitted well to parameter b which was consistent with previous works (Avila & Silva, 1999; Barreiro et al., 1997) The rate constant 262 M Rattanathanalerk et al / Journal of Food Engineering 66 (2005) 259–265 Table Kinetic parameters for color change of pineapple juice k0 (minÀ1 ) · 103 k1 (minÀ1 ) · 103 R2 Parameter Kinetic model T (°C) a=a0 n¼1 55 65 75 85 95 0.50 0.83 1.41 1.79 2.40 0.980 0.950 0.962 0.992 0.972 b=b0 n¼1 55 65 75 85 95 0.52 0.91 1.40 1.87 2.40 0.958 0.996 0.987 0.990 0.985 DE Combined 55 65 75 85 95 25.31 31.64 31.34 46.39 59.96 0.963 0.968 0.996 0.991 0.982 28.73 69.72 81.03 132.31 219.47 increased with the higher heating temperatures This could be explained by the assumption that high temperature accelerated the carotenoid isomerization which led to the loss of yellowness (Chen, Peng, & Chen, 1995; Singleton, Gortner, & Young, 1961) Previous studies of the color change during heat treatment showed similar results Avila and Silva (1999) examined the color degradation of peach puree as affected by heat treatment Peach puree became darker, corresponding to a decrease in L value and an increase in a value, with increasing temperature Moreover, the loss of yellowness was also expressed by a decrease in the b value They concluded that the major causes of color change were due to carotenoid degradation and nonenzymatic browning (Maillard) To describe the total color of pineapple juice, the combination of parameters L, a and b, were determined in terms of total color difference (DE) DE of pineapple juice sample was calculated using Eq (1): 2 1=2 DE ¼ ½ðDLÞ þ ðDaÞ þ ðDbÞ ð1Þ The plot between the total color difference of pineapple juice and time is shown in Fig The results showed that DE increased significantly at higher heating temperatures and prolonged processing times It was also observed that the first portion of the curves exhibited steeper slopes as the heating temperature increased It means that higher temperature accelerated the chemical reactions and most of the color change occurred during the early heating period To describe the reactions closely, the juice samples may be taken more frequently at higher heating temperatures In this current study, the change in DE did not fit simple zero or first order kinetic models Color changes of pineapple juice may be the result of more than one reaction and these reactions may not occur simultaneously at one temperature Therefore, temperature was an important driving force behind the changes in the color of heated samples The results suggested that the change in DE was influenced by both non-enzymatic browning and pigment destruction The combined model was applied to describe the phenomena which occurred during heating of pineapple juice The combined model was used widely to explain the color change in many fruit products (Avila & Silva, 1999; Garza et al., 1999; Ibarz et al., 1999; Lozano & Ibarz, 1997) and was proposed as a two-stage mechanism (Ibarz et al., 1999) The first stage is color formation due to the Maillard reaction which follows a zero order kinetics ðk0 Þ The second stage is destruction of natural fruit pigments which follow first order kinetics ðk1 Þ The combined kinetic model is shown in Eq (2): C ¼ Kc À ðKc À C0 Þ expðÀk1 tÞ ð2Þ Substituting C with DE and DE at initial time is zero (C0 ¼ 0), Eq (2) becomes DE ¼ Kc ½1 À expðÀk1 tÞ ð3Þ where Kc ¼ k0 =k1 In this work, the results showed that the two reactions occurred at a higher rate as temperature increased Kc represents the relation between kinetic constants, k0 (color formation) and k1 (pigment destruction) Kc values greater than indicated that the Maillard reaction predominated over pigment destruction Moreover, the higher the temperature, the higher the value of Kc This suggested that reaction rates were strongly dependent on processing temperatures Many studies of the color changes during heat treatment of fruit puree demonstrated similar finding Ibarz et al (1999) found that a combined model could be used to describe the change of DE in pear puree The Maillard reaction was found to be dominant rather than pigment destruction Garza et al (1999) implied that DE M Rattanathanalerk et al / Journal of Food Engineering 66 (2005) 259–265 263 Table Arrhenius equation parameters for the different variables of pineapple juice a=a0 b=b0 DE Kinetic model n¼1 n¼1 Combined; n ¼ K0 11.46 · 10 9.67 · 102 1.12 · 105 fitted to combined kinetic model and stated that brown color formation was higher than pigment destruction in peach puree The variation in kinetic constants with heating temperature could be described using the Arrhenius relationship The constant parameters obtained from the Arrhenius equation are given in Table In this study, a, b and DE values were chosen to demonstrate the change of pineapple juice color during heating Activation energy values of 39.78, 39.20 and 47.33 kJ/mol were obtained for parameters a, b and DE, respectively These values were found to be lower than those reported in the literature for peach puree (Avila & Silva, 1999; Ibarz et al., 1999) and pear puree (Garza et al., 1999) This could be due to the different type of fruit, which implied the differences in composition such as sugar and amino acid content, total solid content, pH, acidity and also the temperature range of the study (Beveridge & Harrison, 1984; Ahmed, Shivhare, & Kaur, 2002) This was supported by the work of Lozano and Ibarz (1997) Above authors indicated that change in hue during heating was different for each fruit pulp For example, apple pulp was more sensitive to discoloration during heating than plum pulp Therefore, the composition of the products was related to different degrees of heat sensitivity 3.2 5-Hydroxymethylfurfural (HMF) accumulation and brown pigment formation in pineapple juice during heat treatment As non-enzymatic browning is one of the major causes of color change in fruit products, the effect of heating temperature and processing time on the accumulation of HMF and brown pigment formation were Ea (kJ/mol) R2 39.788 39.201 47.336 0.983 0.978 0.962 2.00 1.80 HMT / HMT o Variable 1.60 1.40 1.20 1.00 10 20 30 40 50 60 70 80 90 Heating time (min) Fig The relative value of HMF of pineapple juice samples at different heating temperatures: 55 °C ðrÞ, 65 °C (h), 75 °C (m), 85 °C (s) and 95 °C (d) investigated in this study The relationship between relative HMF content ðHMF=HMF0 Þ and processing time at different temperatures applied is shown in Fig It was observed that heating temperature had a marked effect on the formation of HMF The results indicated that HMF increased linearly with time and the higher amounts were found at the higher heating conditions The relationship between relative A420 ðA420 =A0420 Þ and time was also observed to be linear, similar to HMF development Therefore, zero order kinetics was applied to describe the change of both substances and the equation used is shown as: C ¼ C0 þ k0 t ð4Þ Table shows the values of the kinetic parameters for HMF and brown pigment formation The kinetic constants tended to increase with the processing Table Kinetic parameters for HMF evolution and brown pigment formation of pineapple juice Parameter Kinetic model T (°C) k0 (minÀ1 ) · 103 R2 HMF=HMF0 n¼0 55 65 75 85 95 3.80 5.07 6.76 9.14 12.26 0.971 0.992 0.982 0.989 0.990 A420 =A0420 n¼0 55 65 75 85 95 0.10 0.19 0.31 0.41 0.56 0.973 0.956 0.973 0.988 0.982 264 M Rattanathanalerk et al / Journal of Food Engineering 66 (2005) 259–265 Table Arrhenius parameters for the different variables of pineapple juice Variable Kinetic model K0 Ea (kJ/mol) R2 HMF=HMF0 A420 =A0420 n¼0 n¼0 179.182 724.95 29.401 42.794 0.998 0.977 temperature This indicated that HMF was formed at a higher rate at elevated temperatures and subsequently this phenomenon affected brown pigment formation Several works studied the Maillard reaction in aqueous systems containing glucose and amino acid (Carabasa-Giribet & Ibarz-Ribas, 2000; Gogus, Bozkurt, & Eren, 1998; Reyes, Poocharoen, & Wrolstad, 1982) Garza et al (1999) reported that the HMF content increased with treatment time This increase occurred from with disappearance of the sucrose due to Maillard reaction and sucrose hydrolysis increased with treatment temperature Pineapple juice typically contains sucrose, glucose and fructose (C amara, Dıez, & Torija, 1995) which are the substrates of the Maillard reaction When the temperature increased, the sucrose in the juice was easily hydrolyzed and more glucose and fructose were formed, and thus increased the substrates of the Maillard reaction Moreover, the high temperature accelerated the reaction which is shown by the increase in rate constant values The change in the relative absorbancy at 420 nm ðA420 =A0420 Þ which is related to brown pigment formation was adequately described by zero order kinetics with the high correlation coefficient ðR2 > 0:95Þ The results obtained from this study were consistent with previous works Beveridge and Harrison (1984) studied the effect of temperature (50–80 °C) and soluble solids (45.2–72.5° Bx) on non-enzymatic browning in pear juice concentrate and browning could be modeled as a zero order rate process Cohen et al (1998) reported that the zero order kinetics could be used as a non-enzymatic browning index ðA420 Þ for apple juice (13° Bx) heating at 95–123 °C Comparing the activation energy obtained for HMF=HMF0 to A420 =A0420 it was observed that the activation energy found for HMF formation was lower than that of brown pigment formation The results implied that HMF occurred at a higher rate than the latter substance After heating, HMF retained in the juice would change to a brown pigment during storage Therefore, HMF was proposed as a useful indicator to determine the change of color in the pineapple juice (Table 4) Conclusions The quality degradation of pineapple juice due to heat treatment was studied at temperatures ranging from 55 to 95 °C The changes in Hunter parameters a and b followed first order kinetics while the change in parameter L could not be fitted to any simple relationship Total color difference ðDEÞ could be described using a combined model which included the effect of both nonenzymatic browning and pigment destruction The changes of 5-hydroxymethylfurfural (HMF) and brown pigment formation were chosen to demonstrate the nonenzymatic browning reaction occurring during the study and were found to follow zero order kinetics The results suggested that processing temperatures strongly influenced the reaction rate The Arrhenius model could be used to describe the temperature dependence of the reaction rate constant for all parameters considered A study of quality loss in terms of sugars and amino acids, the substrates of the Maillard reaction, together with carotenoid destruction as affected by heat treatment is recommended for future work References Ahmed, J., Shivhare, U S., & Kaur, M (2002) Thermal color degradation kinetics of mango puree International Journal of Food Properties, 5(2), 359–366 Avila, I M L B., & Silva, C L M (1999) Modeling kinetics of thermal degradation of color in peach puree Journal of Food 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Lozano, J E., & Ibarz, A (1997) Color changes in concentrated fruit pulp during heating at high temperatures Journal of Food Engineering, 31(3), 365–373 Martinez, M V., & Whitaker, J R (1995) The biochemistry and control of enzymatic browning Trends in Food Science and Technology, 6(6), 195–200 265 Mehrlich, F P., & Felton, G E (1980) Pineapple juice In P E Nelson & D K Tressler (Eds.), Fruit and vegetable processing technology (3rd ed., pp 180–211) Connecticut: The AVI Publishing Ranganna, S (1986) Handbook of analysis and quality control for fruit and vegetable products (2nd ed.) New Delhi: Tata McGraw-Hill, pp 498–510 Reyes, F G R., Poocharoen, B., & Wrolstad, R E (1982) Maillard browning reaction of sugar–glycine model systems: Changes in sugar concentration, color and appearance Journal of Food Science, 47(4), 1376–1377 Singleton, V L., Gortner, W A., & Young, H Y (1961) Carotenoid pigments of pineapple fruit I Acid-catalyzed isomerization of the Pigments Journal of Food Science, 26(1), 49–52 ... constant 26 2 M Rattanathanalerk et al / Journal of Food Engineering 66 (20 05) 25 9 26 5 Table Kinetic parameters for color change of pineapple juice k0 (minÀ1 ) · 103 k1 (minÀ1 ) · 103 R2 Parameter... (1993) Kinetics of deterioration of pineapple concentrate Journal of Food Science, 58(6), 1411–1417 M Rattanathanalerk et al / Journal of Food Engineering 66 (20 05) 25 9 26 5 Garza, S., Ibarz, A., Pagan,... 0.56 0.973 0.956 0.973 0.988 0.9 82 264 M Rattanathanalerk et al / Journal of Food Engineering 66 (20 05) 25 9 26 5 Table Arrhenius parameters for the different variables of pineapple juice Variable Kinetic