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Shelf life model of powdered infant formula as function of temperature and oxygen concentration
Food Packaging and Shelf Life xxx (xxxx) xxx–xxx
Contents lists available at ScienceDirect
Food Packaging and Shelf Life journal homepage: www.elsevier.com/locate/fpsl
Shelf life model of powdered infant formula as function of temperature and oxygen concentration Duck Soon An, Ji Hye Lee, Dong Sun Lee
⁎
Department of Food Science and Biotechnology, Kyungnam University, 7 Kyungnamdaehak-ro, Changwon 51767, South Korea
A R T I C L E I N F O
A B S T R A C T
Chemical compounds studied in this article: Acetic acid (PubChem CID: 176) Chloroform (PubChem CID: 6212) n-Hexane (PubChem CID: 8058) Potassium iodide (PubChem CID: 4875) Sodium sulfate anhydrous (PubChem CID: 24436) Sodium thiosulfate (PubChem CID: 24477) Starch (PubChem CID: 439341)
Oxidative quality change is the primary quality factor determining the shelf life of powdered infant formula. In order to develop a shelf life model based on its kinetics, the lipid oxidation progress expressed as increase in peroxide value (POV) was described, for temperatures of 20, 30 and 40 °C and oxygen concentrations of 21.2 and 1.5 kPa, by using Huang’s model. The dependences of the model parameters (induction period and oxidation rate) were formulated as functions of temperature and oxygen concentration by Arrhenius equation and a nonlinear empirical equation, respectively. The time for POV to increase from 3 meq/kg to the limit of 15 meq/ kg was defined as the product shelf life and then determined for ranges of temperature and oxygen concentration. Examination of the developed model suggested that the shelf life can be significantly extended by packaging under O2 concentration below 2 kPa (2% at 1 atm) and storing below 25 °C.
Keywords: Shelf life Oxidation Modified atmosphere Temperature Oxygen
1. Introduction Powdered infant formulas used for meeting the nutritional requirements of human milk are fed to babies after mixing with water. For meeting their nutritional requirements, they are usually manufactured to contain cow's milk protein, vegetable oil, lactose, vitamins, minerals and other functional ingredients such as prebiotics and probiotics. To preserve their quality during shelf life, powdered dairy products including infant formulas are often packaged under modified atmosphere of low oxygen concentration in metal cans or aluminiumlaminated film pouches (Lloyd, Zou, Farnsworth, Ogden, & Pike, 2004; Min, Lee, Lindamood, Chang, & Reineccius, 1989). Even under atmospheres of low oxygen concentration ranging between 2 and 5 kPa, the milk powder products are prone to oxidative deterioration (Lloyd, Hess, & Drake, 2009; Tehrany & Sonneveld, 2009). The reported shelf life varies from 3 months to 3 years. Because the oxidative quality changes depend on temperature and oxygen concentration, shelf life of the infant formula products is expected to be affected by these two factors. Thus, analysing the relationship between the oxidative quality change and the two independent variables will help to design the package and distribution conditions along with shelf life management.
⁎
Therefore, the objective of this study is to establish the functional relationship in the effects of temperature and oxygen concentration on oxidative quality changes of the powdered infant formula, which will lead to a shelf life model. 2. Materials and methods 2.1. Powdered infant formula The infant formula product manufactured by Maeil Dairies Co., Ltd. (Pyeongtaek, Korea) was transported to the laboratory within one week after production. The product manufacturing process consisted of ingredient formulation in liquid state, concentration by evaporation, homogenisation, spray drying and packaging. The composition of the product was given from the manufacturer as 0.12, 0.27, 0.545, 0.035 and 0.03 kg/kg for protein, fat, carbohydrate, ash and moisture, respectively. Aluminium-laminated plastic pouches (polyethylene terephthalate 12 μm/polyethylene 25 μm/aluminium foil 7 μm/polyethylene 65 μm, 3.5 × 17.5 cm) of the product in 13 g unit under N2 gas (residual O2 1.0 kPa) were used to look into the temperature effect (An, Lee, & Lee, 2018): presence of 7 μm aluminium foil in the film layers
Corresponding author at: Department of Food Science and Biotechnology, Kyungnam University, 7 Kyungnamdaehak-ro, Changwon 51767, South Korea. E-mail address: [email protected] (D.S. Lee).
https://doi.org/10.1016/j.fpsl.2017.12.006 Received 2 June 2017; Received in revised form 13 December 2017; Accepted 14 December 2017 2214-2894/ © 2017 Elsevier Ltd. All rights reserved.
Please cite this article as: An, D.S., Food Packaging and Shelf Life (2017), https://doi.org/10.1016/j.fpsl.2017.12.006
Food Packaging and Shelf Life xxx (xxxx) xxx–xxx
D.S. An et al.
may allow assumption of negligible permeation of water vapour ( < 0.1 g m−2 d−1 at 37 °C and 90% relative humidity) and gas ( < 0.1 mL m−2 d−1 atm−1 at 23 °C) (Dixon, 2000); the packages were stored at 20, 30 and 40 °C for 460, 350 and 210 days, respectively. Three-piece tinplate cylindrical cans (inside diameter of 9.9 cm and height of 12.6 cm) containing 400 g of powdered infant formula under air (21.2 kPa O2) or 1.5 kPa O2 (balance of nitrogen) were used to investigate the effect of oxygen concentration: the canned packages were stored at 30 °C for 390 days. The initial package O2 concentration was measured by using a gas chromatograph (Varian CP3800, Palo Alto, CA, USA) for 1 mL of gas sample taken from the can headspace. Silicon glue was applied on the aluminium foil lid of the metal can to help the hermetic gas sampling. The gas chromatograph had been equipped with a thermal conductivity detector and an Alltech CTR I column (Alltech Associates Inc., Deerfield, IL, USA). 2.2. Measurement and kinetic description of product oxidation During the storage, packages were taken out periodically to measure the oxidative quality change of the infant formula. Peroxide value (POV) of the lipid in the stored product as oxidation index was measured following a method modified slightly from Cesa, Casadei, Carreto, & Paolicelli (2012) and Mu, Gao, Chen, Tao, Fang, & Ge (2013): sixty gram sample from 5 pouches or a can was added sequentially with 150 mL of n-hexane (Samchun, Pyoengtaek, South Korea) and 12 g of sodium sulfate anhydrous (Sigma-Aldrich, Co., St. Louis, USA), and the mixture was stirred magnetically under darkness for 1 h. The mixture was then filtered through filter paper (No. 20, Hyundai Micro, Seoul, South Korea) to collect the filtrate. The hexane was evaporated inside a vacuum desiccator at room temperature in the darkness for 1 day and then the lipid residue of 0.5 g was weighed for dissolution in 25 mL of mixture of chloroform (Daesung Co., Siheung, South Korea) and glacial acetic acid (Samchun Co., Pyoengtaek, South Korea) (2:3, v/v). Then saturated potassium iodide (Alfa Aesar, Haverhill, Massachusetts, USA) solution (1 mL) was added for reaction with the peroxides. The mixture was shaken completely for 1 min and was then left under darkness for 10 min. Thirty millilitres of distilled water and 1 mL of 1% w/v starch indicator (Alfa Aesar, Haverhill, Massachusetts, USA) solution were added. The mixture was titrated against 0.01N sodium thiosulfate until its colour changes from dark to clear. The blank test was conducted with distilled water of 0.5 mL instead of 0.5 g lipid under the same procedure. POV was expressed in meq/kg lipid matter. The increase phase of POV was fitted by Huang’s three parameter model (Huang, 2011), which had been previously used for describing the oxidation progress in food system (Lee & Yam, 2013; Zhu, Lee, & Yam, 2012).
1 + exp[−25(t − λ )] ⎫ 1 ) ln( POV = POVo + km ⎧t + ⎬ ⎨ 1 + exp(25λ ) 25 ⎭ ⎩
Fig. 1. (A) POV increase of powdered infant formula in N2-flushed packages at different temperatures and (B) temperature dependence of its kinetic parameters according to Arrhenius equation.
of interest in terms of food shelf life determination, because the latter phase of POV decrease after the maximum is already beyond the critical limit of affordable quality. Thus, the phase of POV increase was analysed according to Eq. (1) for kinetic study as shown in Fig. 1(A). In general, Huang’s model described POV data well even though there is some discrepancy from the experimental data for 56 and 84 days at 30 °C. Higher temperature tended to trigger onset of POV earlier and enhance its increase rate, resulting in shorter induction period (λ) and higher maximum oxidation rate (km) as presented in Fig. 1. Arrhenius equation could be applied to explain the temperature dependence of (1/ λ) and km (Calligaris, Manzocco, Kravina, & Nicoli, 2007):
(1/ λ ) = (1/ λ o )exp(−
km = km, o exp(−
Ea, λ ) RT
Ea, k ) RT
(2) (3)
where Ea,λ and Ea,k are activation energies for 1/λ and km, respectively, and λo and km,o are constants. Ea,λ and Ea,k obtained from Fig. 1(B) were 31.25 and 61.75 kJ/mol, respectively, which can be used for taking into account the temperature dependence of oxidation. Fig. 2(A) shows the increase of POV in the samples packaged under two different oxygen concentrations. High oxygen concentration caused fast onset and high rate of oxidation as given with the shorter induction period (λ) and the higher maximum oxidation rate constant (km) in Table 1. In order to express the oxidation rate as function of oxygen concentration, a commonly used empirical relationship in nonlinear form was applied to induction period and oxidation rate constant (Karel, 1992):
(1)
where POV is peroxide value at time t (meq/kg), t is time of storage (d), POVo is initial peroxide value (meq/kg), km is maximum oxidation rate constant (meq kg−1 d−1) and λ is induction period (d). The parameters (λ and km) obtained from the POV increase curve by nonlinear regression of Levenberg-Marquardt method (Motulsky & Christopoulos, 2004) were used for quantifying the dependence of oxidation on temperature and oxygen concentration. 3. Results and discussion
v= Fig. 1 shows the effect of storage temperature on the evolution of POV in the lipid of the formula product in N2 atmosphere. In the prolonged storage, POV started to decline after reaching a maximum, which is usually observed in the course of lipid oxidation and is attributed to the unstable nature of hydroperoxides (An et al., 2018; Nawar, 1985; van Boekel, 2009). The phase of POV increase is mainly
C1 [O2] C2 + [O2]
(4)
where v is inverse of induction period or maximum oxidation rate constant, [O2] is oxygen concentration (kPa), C1 and C2 are constants. Table 2 presents the parameters of Eq. (4) determined from two conditions of Table 1, which quantitatively show the influence of oxygen concentration on oxidation rate in Fig. 2(B). Oxidation was 2
Food Packaging and Shelf Life xxx (xxxx) xxx–xxx
D.S. An et al.
Fig. 3. Shelf life of the powdered infant formula as function of temperature and oxygen concentration.
2012). Fig. 3 shows the shelf life as function of temperature and package oxygen concentration. The shelf life is highly dependent on oxygen concentration below 5 kPa (5% at 1 atm). Temperature effect on the shelf life is pronounced in lower temperatures of 20–25 °C. At low oxygen concentrations, the temperature effect is less significant compared to oxygen concentration effect as observed for whole milk powder by Lloyd et al. (2009). In overall picture significantly extended shelf life ( > 250 days) can be obtained below oxygen concentration below 2 kPa (2% at 1 atm) and storage temperature below 25 °C. For example, shelf life longer than 470 days can be provided under O2 concentration below 1 kPa (1% at 1 atm) and temperature below 23 °C, while the higher temperature above 30 °C can give shelf life of only 142 days even at O2 concentration of 3 kPa (3% at 1 atm). In this study, a shelf life model was built on the basis of oxidation kinetics which adopted the functional relationships commonly used in temperature and oxygen concentration dependences. The shelf life estimates of Fig. 3 are also based on the arbitrarily assumed conditions of initial state and critical limits in oxidation levels. The estimation is understood to depend on the assumptions of kinetic relationships and critical quality level. The magnitude of shelf life estimates may be different with the assumed conditions and is meaningful to a limited extent. However, the general tendency of Fig. 3 in temperature and oxygen concentration dependences would be still valid for different conditions.
Fig. 2. (A) Effect of O2 concentration on POV increase of powdered infant formula at 30 °C and (B) its kinetic representation according to Eq. (4).
Table 1 Oxidation model parameters of Eq. (1) describing POV increase for two different oxygen concentrations ([O2]) used for packaging the powdered infant formula (Fig. 2(A)). [O2] (kPa)
21.2 1.5
Parameters of Eq. (1) λ (d)
km (meq kg−1 d−1)
14.481 69.076
0.186 0.084
Table 2 Parameters of Eq. (4) showing oxygen dependence of oxidation progress parameters of the powdered infant formula. Parameters of Eq. (1)
1/λ km
Parameters of Eq. (4) C1 (d−1 or meq kg−1 d−1)
C2 (kPa)
0.097 0.205
8.713 2.215
4. Conclusions Lipid oxidation kinetics in POV increase was established for the powdered infant formula and applied to develop its shelf model as function of temperature and oxygen concentration. The analysis tells that significantly extended shelf life can be provided by packaging under O2 concentration below 2 kPa (2% at 1 atm) and storing below 25 °C. The shelf life model presented in this study provides the direction for selecting desired packaging and storage temperature, which will be useful for shelf life management combined with target market.
significantly higher above [O2] of 3 kPa in terms of both λ and km. This is in general agreement with industrial guideline that the milk powder should be packaged in inert gas atmosphere with O2 concentration below 2 kPa (Robertson, 2013). Now the oxygen dependence model of Eq. (4) was combined with Arrhenius relationship (Eqs. (2) and (3)) using respective activation energies of 31.25 and 61.75 kJ/mol for 1/λ or km, which were determined above (Fig. 1). The shelf life (ts) was estimated from the simple relationship substituting λ and km into Eq. (5) for any combinations of 20–40 °C temperature and 0.5–21 kPa oxygen partial pressure:
ts = λ +
POVc − POVo km
Acknowledgment This work was supported by the Ministry of Agriculture, Food and Rural Affairs, Korea (Project #314046-3).
(5)
References
where POVo and POVc are initial and critical levels of peroxide values, which were set arbitrarily as 3 and 15 meq/kg, respectively. It was noted that 10–20 meq/kg of POV has often been used as quality limit at the end of shelf life for fatty foods (Calligaris et al., 2007; Jena & Das,
An, D. S., Lee, J. H., & Lee, D. S. (2018). Water vapor and oxygen barrier estimation in designing a single-serve package of powdered infant formula for required shelf life. Journal of Food Process Engineering, 41, e12592. http://dx.doi.org/10.1111/jfpe. 12592.
3
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temperature on flavor and shelf-life of whole milk powder. Journal of Dairy Science, 92, 2409–2422. Min, D. B., Lee, S. H., Lindamood, J. B., Chang, K. S., & Reineccius, G. A. (1989). Effects of packaging conditions on the flavor stability of dry whole milk. Journal of Food Science, 54, 1222–1224. Motulsky, H., & Christopoulos, A. (2004). Fitting models to biological data using linear and nonlinear regression. New York, NY, USA: Oxford Unversity Press. Mu, H., Gao, H., Chen, H., Tao, F., Fang, X., & Ge, L. (2013). A nanosised oxygen scavenger: Preparation and antioxidant application to roasted sunflower seeds and walnuts. Food Chemistry, 136, 245–250. Nawar, W. W. (1985). Lipids. In O. Fennema (Ed.). Food chemistry (pp. 139–244). New York, USA: Marcel Dekker. Robertson, G. L. (2013). Food packaging: Principles and practice (3rd). Boca Raton, FL, USA: CRC Press. Tehrany, E. A., & Sonneveld, K. (2009). Packaging and the shelf life of milk powders. In G. L. Robertson (Ed.). Food packaging and shelf life (pp. 127–141). Boca Raton, FL, USA: CRC Press. Zhu, X., Lee, D. S., & Yam, K. L. (2012). Release property and antioxidant effectiveness of tocopherol-incorporated LDPE/PP blend films. Food Additives & Contaminants, 29, 461–468. van Boekel, M. A. J. S. (2009). Kinetic modeling of reactions in foods. Boca Raton, FL, USA: CRC Press.
Calligaris, S., Manzocco, L., Kravina, G., & Nicoli, M. C. (2007). Shelf-life modeling of bakery products by using oxidation indices. Journal of Agricultural and Food Chemistry, 55, 2004–2009. Cesa, S., Casadei, M. A., Cerreto, F., & Paolicelli, P. (2012). Influence of fat extraction methods on the peroxide value in infant formulas. Food Research International, 48, 584–591. Dixon, J. (2000). Development of flexible plastics packaging. In G. A. Giles, & D. R. Bain (Eds.). Materials and development of plastics packaging for the consumer market (pp. 79– 104). Sheffield: Sheffield Academic Press. Huang, L. (2011). A new mechanistic growth model for simultaneous determination of lag phase duration and exponential growth rate and a new Belehdradek-type model for evaluating the effect of temperature on growth rate. Food Microbiology, 28, 770–776. Jena, S., & Das, H. (2012). Shelf life prediction of aluminum foil laminated polyethylene packed vacuum dried coconut milk powder. Journal of Food Engineering, 108, 135–142. Karel, M. (1992). Kinetics of lipid oxidation. In H. G. Schwartzberg, & R. W. Hartel (Eds.). Physical chemistry of foods (pp. 651–668). New York, USA: Marcel Dekker. Lee, D. S., & Yam, K. L. (2013). Effect of tocopherol loading and diffusivity on effectiveness of antioxidant packaging. CyTA-Journal of Food, 11, 89–93. Lloyd, M. A., Zou, J., Farnsworth, H., Ogden, L. V., & Pike, O. A. (2004). Quality at time of purchase of dried milk products commercially packaged in reduced oxygen atmosphere. Journal of Dairy Science, 87, 2337–2343. Lloyd, M. A., Hess, S. J., & Drake, M. A. (2009). Effect of nitrogen flushing and storage
4
Contents lists available at ScienceDirect
Food Packaging and Shelf Life journal homepage: www.elsevier.com/locate/fpsl
Shelf life model of powdered infant formula as function of temperature and oxygen concentration Duck Soon An, Ji Hye Lee, Dong Sun Lee
⁎
Department of Food Science and Biotechnology, Kyungnam University, 7 Kyungnamdaehak-ro, Changwon 51767, South Korea
A R T I C L E I N F O
A B S T R A C T
Chemical compounds studied in this article: Acetic acid (PubChem CID: 176) Chloroform (PubChem CID: 6212) n-Hexane (PubChem CID: 8058) Potassium iodide (PubChem CID: 4875) Sodium sulfate anhydrous (PubChem CID: 24436) Sodium thiosulfate (PubChem CID: 24477) Starch (PubChem CID: 439341)
Oxidative quality change is the primary quality factor determining the shelf life of powdered infant formula. In order to develop a shelf life model based on its kinetics, the lipid oxidation progress expressed as increase in peroxide value (POV) was described, for temperatures of 20, 30 and 40 °C and oxygen concentrations of 21.2 and 1.5 kPa, by using Huang’s model. The dependences of the model parameters (induction period and oxidation rate) were formulated as functions of temperature and oxygen concentration by Arrhenius equation and a nonlinear empirical equation, respectively. The time for POV to increase from 3 meq/kg to the limit of 15 meq/ kg was defined as the product shelf life and then determined for ranges of temperature and oxygen concentration. Examination of the developed model suggested that the shelf life can be significantly extended by packaging under O2 concentration below 2 kPa (2% at 1 atm) and storing below 25 °C.
Keywords: Shelf life Oxidation Modified atmosphere Temperature Oxygen
1. Introduction Powdered infant formulas used for meeting the nutritional requirements of human milk are fed to babies after mixing with water. For meeting their nutritional requirements, they are usually manufactured to contain cow's milk protein, vegetable oil, lactose, vitamins, minerals and other functional ingredients such as prebiotics and probiotics. To preserve their quality during shelf life, powdered dairy products including infant formulas are often packaged under modified atmosphere of low oxygen concentration in metal cans or aluminiumlaminated film pouches (Lloyd, Zou, Farnsworth, Ogden, & Pike, 2004; Min, Lee, Lindamood, Chang, & Reineccius, 1989). Even under atmospheres of low oxygen concentration ranging between 2 and 5 kPa, the milk powder products are prone to oxidative deterioration (Lloyd, Hess, & Drake, 2009; Tehrany & Sonneveld, 2009). The reported shelf life varies from 3 months to 3 years. Because the oxidative quality changes depend on temperature and oxygen concentration, shelf life of the infant formula products is expected to be affected by these two factors. Thus, analysing the relationship between the oxidative quality change and the two independent variables will help to design the package and distribution conditions along with shelf life management.
⁎
Therefore, the objective of this study is to establish the functional relationship in the effects of temperature and oxygen concentration on oxidative quality changes of the powdered infant formula, which will lead to a shelf life model. 2. Materials and methods 2.1. Powdered infant formula The infant formula product manufactured by Maeil Dairies Co., Ltd. (Pyeongtaek, Korea) was transported to the laboratory within one week after production. The product manufacturing process consisted of ingredient formulation in liquid state, concentration by evaporation, homogenisation, spray drying and packaging. The composition of the product was given from the manufacturer as 0.12, 0.27, 0.545, 0.035 and 0.03 kg/kg for protein, fat, carbohydrate, ash and moisture, respectively. Aluminium-laminated plastic pouches (polyethylene terephthalate 12 μm/polyethylene 25 μm/aluminium foil 7 μm/polyethylene 65 μm, 3.5 × 17.5 cm) of the product in 13 g unit under N2 gas (residual O2 1.0 kPa) were used to look into the temperature effect (An, Lee, & Lee, 2018): presence of 7 μm aluminium foil in the film layers
Corresponding author at: Department of Food Science and Biotechnology, Kyungnam University, 7 Kyungnamdaehak-ro, Changwon 51767, South Korea. E-mail address: [email protected] (D.S. Lee).
https://doi.org/10.1016/j.fpsl.2017.12.006 Received 2 June 2017; Received in revised form 13 December 2017; Accepted 14 December 2017 2214-2894/ © 2017 Elsevier Ltd. All rights reserved.
Please cite this article as: An, D.S., Food Packaging and Shelf Life (2017), https://doi.org/10.1016/j.fpsl.2017.12.006
Food Packaging and Shelf Life xxx (xxxx) xxx–xxx
D.S. An et al.
may allow assumption of negligible permeation of water vapour ( < 0.1 g m−2 d−1 at 37 °C and 90% relative humidity) and gas ( < 0.1 mL m−2 d−1 atm−1 at 23 °C) (Dixon, 2000); the packages were stored at 20, 30 and 40 °C for 460, 350 and 210 days, respectively. Three-piece tinplate cylindrical cans (inside diameter of 9.9 cm and height of 12.6 cm) containing 400 g of powdered infant formula under air (21.2 kPa O2) or 1.5 kPa O2 (balance of nitrogen) were used to investigate the effect of oxygen concentration: the canned packages were stored at 30 °C for 390 days. The initial package O2 concentration was measured by using a gas chromatograph (Varian CP3800, Palo Alto, CA, USA) for 1 mL of gas sample taken from the can headspace. Silicon glue was applied on the aluminium foil lid of the metal can to help the hermetic gas sampling. The gas chromatograph had been equipped with a thermal conductivity detector and an Alltech CTR I column (Alltech Associates Inc., Deerfield, IL, USA). 2.2. Measurement and kinetic description of product oxidation During the storage, packages were taken out periodically to measure the oxidative quality change of the infant formula. Peroxide value (POV) of the lipid in the stored product as oxidation index was measured following a method modified slightly from Cesa, Casadei, Carreto, & Paolicelli (2012) and Mu, Gao, Chen, Tao, Fang, & Ge (2013): sixty gram sample from 5 pouches or a can was added sequentially with 150 mL of n-hexane (Samchun, Pyoengtaek, South Korea) and 12 g of sodium sulfate anhydrous (Sigma-Aldrich, Co., St. Louis, USA), and the mixture was stirred magnetically under darkness for 1 h. The mixture was then filtered through filter paper (No. 20, Hyundai Micro, Seoul, South Korea) to collect the filtrate. The hexane was evaporated inside a vacuum desiccator at room temperature in the darkness for 1 day and then the lipid residue of 0.5 g was weighed for dissolution in 25 mL of mixture of chloroform (Daesung Co., Siheung, South Korea) and glacial acetic acid (Samchun Co., Pyoengtaek, South Korea) (2:3, v/v). Then saturated potassium iodide (Alfa Aesar, Haverhill, Massachusetts, USA) solution (1 mL) was added for reaction with the peroxides. The mixture was shaken completely for 1 min and was then left under darkness for 10 min. Thirty millilitres of distilled water and 1 mL of 1% w/v starch indicator (Alfa Aesar, Haverhill, Massachusetts, USA) solution were added. The mixture was titrated against 0.01N sodium thiosulfate until its colour changes from dark to clear. The blank test was conducted with distilled water of 0.5 mL instead of 0.5 g lipid under the same procedure. POV was expressed in meq/kg lipid matter. The increase phase of POV was fitted by Huang’s three parameter model (Huang, 2011), which had been previously used for describing the oxidation progress in food system (Lee & Yam, 2013; Zhu, Lee, & Yam, 2012).
1 + exp[−25(t − λ )] ⎫ 1 ) ln( POV = POVo + km ⎧t + ⎬ ⎨ 1 + exp(25λ ) 25 ⎭ ⎩
Fig. 1. (A) POV increase of powdered infant formula in N2-flushed packages at different temperatures and (B) temperature dependence of its kinetic parameters according to Arrhenius equation.
of interest in terms of food shelf life determination, because the latter phase of POV decrease after the maximum is already beyond the critical limit of affordable quality. Thus, the phase of POV increase was analysed according to Eq. (1) for kinetic study as shown in Fig. 1(A). In general, Huang’s model described POV data well even though there is some discrepancy from the experimental data for 56 and 84 days at 30 °C. Higher temperature tended to trigger onset of POV earlier and enhance its increase rate, resulting in shorter induction period (λ) and higher maximum oxidation rate (km) as presented in Fig. 1. Arrhenius equation could be applied to explain the temperature dependence of (1/ λ) and km (Calligaris, Manzocco, Kravina, & Nicoli, 2007):
(1/ λ ) = (1/ λ o )exp(−
km = km, o exp(−
Ea, λ ) RT
Ea, k ) RT
(2) (3)
where Ea,λ and Ea,k are activation energies for 1/λ and km, respectively, and λo and km,o are constants. Ea,λ and Ea,k obtained from Fig. 1(B) were 31.25 and 61.75 kJ/mol, respectively, which can be used for taking into account the temperature dependence of oxidation. Fig. 2(A) shows the increase of POV in the samples packaged under two different oxygen concentrations. High oxygen concentration caused fast onset and high rate of oxidation as given with the shorter induction period (λ) and the higher maximum oxidation rate constant (km) in Table 1. In order to express the oxidation rate as function of oxygen concentration, a commonly used empirical relationship in nonlinear form was applied to induction period and oxidation rate constant (Karel, 1992):
(1)
where POV is peroxide value at time t (meq/kg), t is time of storage (d), POVo is initial peroxide value (meq/kg), km is maximum oxidation rate constant (meq kg−1 d−1) and λ is induction period (d). The parameters (λ and km) obtained from the POV increase curve by nonlinear regression of Levenberg-Marquardt method (Motulsky & Christopoulos, 2004) were used for quantifying the dependence of oxidation on temperature and oxygen concentration. 3. Results and discussion
v= Fig. 1 shows the effect of storage temperature on the evolution of POV in the lipid of the formula product in N2 atmosphere. In the prolonged storage, POV started to decline after reaching a maximum, which is usually observed in the course of lipid oxidation and is attributed to the unstable nature of hydroperoxides (An et al., 2018; Nawar, 1985; van Boekel, 2009). The phase of POV increase is mainly
C1 [O2] C2 + [O2]
(4)
where v is inverse of induction period or maximum oxidation rate constant, [O2] is oxygen concentration (kPa), C1 and C2 are constants. Table 2 presents the parameters of Eq. (4) determined from two conditions of Table 1, which quantitatively show the influence of oxygen concentration on oxidation rate in Fig. 2(B). Oxidation was 2
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D.S. An et al.
Fig. 3. Shelf life of the powdered infant formula as function of temperature and oxygen concentration.
2012). Fig. 3 shows the shelf life as function of temperature and package oxygen concentration. The shelf life is highly dependent on oxygen concentration below 5 kPa (5% at 1 atm). Temperature effect on the shelf life is pronounced in lower temperatures of 20–25 °C. At low oxygen concentrations, the temperature effect is less significant compared to oxygen concentration effect as observed for whole milk powder by Lloyd et al. (2009). In overall picture significantly extended shelf life ( > 250 days) can be obtained below oxygen concentration below 2 kPa (2% at 1 atm) and storage temperature below 25 °C. For example, shelf life longer than 470 days can be provided under O2 concentration below 1 kPa (1% at 1 atm) and temperature below 23 °C, while the higher temperature above 30 °C can give shelf life of only 142 days even at O2 concentration of 3 kPa (3% at 1 atm). In this study, a shelf life model was built on the basis of oxidation kinetics which adopted the functional relationships commonly used in temperature and oxygen concentration dependences. The shelf life estimates of Fig. 3 are also based on the arbitrarily assumed conditions of initial state and critical limits in oxidation levels. The estimation is understood to depend on the assumptions of kinetic relationships and critical quality level. The magnitude of shelf life estimates may be different with the assumed conditions and is meaningful to a limited extent. However, the general tendency of Fig. 3 in temperature and oxygen concentration dependences would be still valid for different conditions.
Fig. 2. (A) Effect of O2 concentration on POV increase of powdered infant formula at 30 °C and (B) its kinetic representation according to Eq. (4).
Table 1 Oxidation model parameters of Eq. (1) describing POV increase for two different oxygen concentrations ([O2]) used for packaging the powdered infant formula (Fig. 2(A)). [O2] (kPa)
21.2 1.5
Parameters of Eq. (1) λ (d)
km (meq kg−1 d−1)
14.481 69.076
0.186 0.084
Table 2 Parameters of Eq. (4) showing oxygen dependence of oxidation progress parameters of the powdered infant formula. Parameters of Eq. (1)
1/λ km
Parameters of Eq. (4) C1 (d−1 or meq kg−1 d−1)
C2 (kPa)
0.097 0.205
8.713 2.215
4. Conclusions Lipid oxidation kinetics in POV increase was established for the powdered infant formula and applied to develop its shelf model as function of temperature and oxygen concentration. The analysis tells that significantly extended shelf life can be provided by packaging under O2 concentration below 2 kPa (2% at 1 atm) and storing below 25 °C. The shelf life model presented in this study provides the direction for selecting desired packaging and storage temperature, which will be useful for shelf life management combined with target market.
significantly higher above [O2] of 3 kPa in terms of both λ and km. This is in general agreement with industrial guideline that the milk powder should be packaged in inert gas atmosphere with O2 concentration below 2 kPa (Robertson, 2013). Now the oxygen dependence model of Eq. (4) was combined with Arrhenius relationship (Eqs. (2) and (3)) using respective activation energies of 31.25 and 61.75 kJ/mol for 1/λ or km, which were determined above (Fig. 1). The shelf life (ts) was estimated from the simple relationship substituting λ and km into Eq. (5) for any combinations of 20–40 °C temperature and 0.5–21 kPa oxygen partial pressure:
ts = λ +
POVc − POVo km
Acknowledgment This work was supported by the Ministry of Agriculture, Food and Rural Affairs, Korea (Project #314046-3).
(5)
References
where POVo and POVc are initial and critical levels of peroxide values, which were set arbitrarily as 3 and 15 meq/kg, respectively. It was noted that 10–20 meq/kg of POV has often been used as quality limit at the end of shelf life for fatty foods (Calligaris et al., 2007; Jena & Das,
An, D. S., Lee, J. H., & Lee, D. S. (2018). Water vapor and oxygen barrier estimation in designing a single-serve package of powdered infant formula for required shelf life. Journal of Food Process Engineering, 41, e12592. http://dx.doi.org/10.1111/jfpe. 12592.
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Food Packaging and Shelf Life xxx (xxxx) xxx–xxx
D.S. An et al.
temperature on flavor and shelf-life of whole milk powder. Journal of Dairy Science, 92, 2409–2422. Min, D. B., Lee, S. H., Lindamood, J. B., Chang, K. S., & Reineccius, G. A. (1989). Effects of packaging conditions on the flavor stability of dry whole milk. Journal of Food Science, 54, 1222–1224. Motulsky, H., & Christopoulos, A. (2004). Fitting models to biological data using linear and nonlinear regression. New York, NY, USA: Oxford Unversity Press. Mu, H., Gao, H., Chen, H., Tao, F., Fang, X., & Ge, L. (2013). A nanosised oxygen scavenger: Preparation and antioxidant application to roasted sunflower seeds and walnuts. Food Chemistry, 136, 245–250. Nawar, W. W. (1985). Lipids. In O. Fennema (Ed.). Food chemistry (pp. 139–244). New York, USA: Marcel Dekker. Robertson, G. L. (2013). Food packaging: Principles and practice (3rd). Boca Raton, FL, USA: CRC Press. Tehrany, E. A., & Sonneveld, K. (2009). Packaging and the shelf life of milk powders. In G. L. Robertson (Ed.). Food packaging and shelf life (pp. 127–141). Boca Raton, FL, USA: CRC Press. Zhu, X., Lee, D. S., & Yam, K. L. (2012). Release property and antioxidant effectiveness of tocopherol-incorporated LDPE/PP blend films. Food Additives & Contaminants, 29, 461–468. van Boekel, M. A. J. S. (2009). Kinetic modeling of reactions in foods. Boca Raton, FL, USA: CRC Press.
Calligaris, S., Manzocco, L., Kravina, G., & Nicoli, M. C. (2007). Shelf-life modeling of bakery products by using oxidation indices. Journal of Agricultural and Food Chemistry, 55, 2004–2009. Cesa, S., Casadei, M. A., Cerreto, F., & Paolicelli, P. (2012). Influence of fat extraction methods on the peroxide value in infant formulas. Food Research International, 48, 584–591. Dixon, J. (2000). Development of flexible plastics packaging. In G. A. Giles, & D. R. Bain (Eds.). Materials and development of plastics packaging for the consumer market (pp. 79– 104). Sheffield: Sheffield Academic Press. Huang, L. (2011). A new mechanistic growth model for simultaneous determination of lag phase duration and exponential growth rate and a new Belehdradek-type model for evaluating the effect of temperature on growth rate. Food Microbiology, 28, 770–776. Jena, S., & Das, H. (2012). Shelf life prediction of aluminum foil laminated polyethylene packed vacuum dried coconut milk powder. Journal of Food Engineering, 108, 135–142. Karel, M. (1992). Kinetics of lipid oxidation. In H. G. Schwartzberg, & R. W. Hartel (Eds.). Physical chemistry of foods (pp. 651–668). New York, USA: Marcel Dekker. Lee, D. S., & Yam, K. L. (2013). Effect of tocopherol loading and diffusivity on effectiveness of antioxidant packaging. CyTA-Journal of Food, 11, 89–93. Lloyd, M. A., Zou, J., Farnsworth, H., Ogden, L. V., & Pike, O. A. (2004). Quality at time of purchase of dried milk products commercially packaged in reduced oxygen atmosphere. Journal of Dairy Science, 87, 2337–2343. Lloyd, M. A., Hess, S. J., & Drake, M. A. (2009). Effect of nitrogen flushing and storage
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