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Influence of headspace oxygen on quality and shelf life of extra virgin olive oil during storage
Food Packaging and Shelf Life 23 (2020) 100433
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Influence of headspace oxygen on quality and shelf life of extra virgin olive oil during storage
T
Basheer M. Iqdiama, Bruce A Weltb,*, Renee Goodrich-Schneidera, Charles A Simsa, George L. Baker IVa, Maurice R. Marshalla a b
Food Science and Human Nutrition Department, University of Florida, Gainesville, FL 32611, United States Agricultural & Biological Engineering Department, University of Florida, Gainesville, FL 32611, United States
A R T I C LE I N FO
A B S T R A C T
Keywords: Extra virgin olive oil Modified atmosphere packaging Shelf life Oxygen Quality
This study evaluated the impact of low O2 headspace in clear and dark containers at different storage temperatures (10 °C and 28 °C) on the quality and shelf life of extra virgin olive oil (EVOO). Bottle headspace was controlled at four different O2 concentrations 2, 5, 10, and 21%. Quality parameters were determined after 3, 6, 9, and 12 months storage: free fatty acids, peroxide value, absorption coefficients K270 and K230, total polyphenols, chlorophyll content, oxidative stability index, and color. Results show low headspace oxygen levels of 2 and 5%, significantly increased EVOO shelf life stored in dark and clear bottles at 10 °C. While the improvement in EVOO shelf-life was less when stored at 28 °C. No significant differences occurred between EVOO samples packaged at 10 and 21% headspace O2 concentrations in clear bottles stored at 28 °C while significant differences were observed with 2 and 5% headspace O2 concentrations. These results suggest that it is important to minimize headspace oxygen in packages of extra virgin olive oil.
1. Introduction Extra virgin olive oil (EVOO) may have nutritional, therapeutic, and gastronomic benefits compared with other olive oil categories (Bajoub, 2016; Calvo, Castaño, Lozano, & González-Gómez, 2012; Caponio, Bilancia, Pasqualone, Sikorska, & Gomes, 2005; Frankel, 2010; LermaGarcía et al., 2009; Romani et al., 2007). Chemically, EVOO may be the best olive oil for its organoleptic characteristics, stability and chemical composition. EVOO is the oil of the olive fruit that is picked at optimum maturity index and correctly processed. EVOO is the only vegetable oil that can be consumed directly in its raw state and contains important nutritional elements (European Communities, 1991; International Olive Oil Council, 1996). The unique characteristics of EVOO are sufficiently valuable to warrant special care in packaging and storage. Proper packaging is critical to preserve nutrition, flavor and color attributes of EVOO (Caponio et al., 2005; Cecchi, Passamonti, & Cecchi, 2010; Romani et al., 2007). The quality and shelf-life of edible oil is limited by oxidation, and this constitutes a major factor for quality deterioration of EVOO during storage (Frankel, 2010, 2014; Nobile, Ambrosino, Sacchi, & Masi, 2003; Parenti, Spugnoli, Masella, & Calamai, 2007; Pristouri, Badeka, & Kontominas, 2010). Oxidation causes oil to become rancid and
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unsuitable for human consumption (Morales & Przybylski, 2013). Light, temperature, headspace oxygen, natural antioxidant content, and the oxygen dissolved in EVOO when bottled are factors that most influence on the level of oxidation during storage. Moreover, oxygen concentration in the oil prior to packaging, initial headspace oxygen partial pressure, oxygen permeability through packaging are important factors influencing deterioration of lipids and overall EVOO quality and shelflife during storage (Del Nobile, Bove, La Notte, & Sacchi, 2003; Parenti et al., 2007; Pristouri et al., 2010). Dark containers, optimal package oxygen barrier properties, and low temperatures during storage are helpful in preserving EVOO quality (Caponio et al., 2005; Cecchi et al., 2010; Cosio, Ballabio, Benedetti, & Gigliotti, 2007; Pristouri et al., 2010). Most previous studies have focused on the type of packaging materials, light transmission, temperature, and time of storage on quality, sensory attributes, and shelf-life of EVOO (Calvo et al., 2012; Caponio et al., 2005; Cecchi et al., 2010; Méndez & Falqué, 2007; Pristouri et al., 2010). While there is an absence of information on how reducing or controlling the O2 headspace concentration in the package influences quality, shelf-life, and preferred sensory characteristics of EVOO. Due to the gap in information concerning the optimum package headspace O2 concentration during storage, additional research is needed to quantify potential benefits of
Corresponding author at: Department of Agricultural and Biological Engineering, 229 Frazier Rogers Hall, PO Box 110570 Gainesville, FL 32611, United States. E-mail address: bwelt@ufl.edu (B.A. Welt).
https://doi.org/10.1016/j.fpsl.2019.100433 Received 18 December 2018; Received in revised form 17 October 2019; Accepted 28 October 2019 2214-2894/ © 2019 Elsevier Ltd. All rights reserved.
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Ethanol, diethyl ether (pro analysis grade), sodium thiosulphate, potassium iodine, sodium hydroxide, acetic acid, chloroform, and cyclohexane for the determination of the free fatty acids (FFA), peroxide value (PV), and absorption coefficients (K232, K270) were purchased from Fisher Scientific (Fisher Scientific, MO, USA).
foil) glass jars (300 mL) purchased from Fischer Scientific (Fisher Scientific, MO, USA) and hermetically sealed (Fig. 1). The preferred barrier properties of the glass material and the accuracy of sealed were the major factors of selecting the type of jar. Jar has a neck having an in-turned flange at its upper end and two vertically spaced, horizontal inward-formed beads with two outward-downward conical surfaces above and below the lower inward-formed beads. The vacuum seal cap of the jar contains a plastic lid that keeps it airtight. The cap has a top disk with a depending short inner skirt having a tapered edge and an elongated peripheral skirt. The in-turned flange of the neck is compressed between the two cap skirts, the upper internal bead seats against the upper conical surface and the locking bead seats in the lower inward-formed bead of the neck. Thus a product and air-tight multi-zone seal is effected; and, further, once seated the cap is tamperproof in that it must be opened or tear to be removed. Headspace volumes were 50 mL after placing the oil in jars. Jars were placed in a hermetically sealed glove box (Fig. 2). Four different oxygen concentrations were applied to the oil samples 21% oxygen (control/ normal atmosphere pressure); and 10% oxygen; 5% oxygen; and 2% oxygen (at atmosphere pressure). The glove box was equipped with inlet and outlet gas valves that were used to modify the atmosphere within the glove box. A gas mixer (Multi-Component Gas Mixing System Series 4000, Environics, Inc. CT, USA) was used with compressed are and nitrogen sourced from the gas port of a liquid nitrogen cryogenic dewar. Glove box outlet gas was discharged through water placed in a glass beaker to avoid atmospheric air flowing backward into the glove box when changing gas bottles or dewars. After achieving desired oxygen concentrations within the glove box, oil containers were sealed within the glove box. Samples in clear and dark containers were removed and stored at two different temperatures: room temperature (25–28 °C) and in an environmental chamber set to 10 °C for 3, 6, 9, and 12 months.
2.2. Olive oil samples
2.4. Headspace oxygen concentration measurement
EVOO was obtained from a local mill in Ocala, FL (crop season 2017), and its quality characteristics at the beginning of the study are identified. Olives of different cultivars (Arbequina, Koroneiki, and Leccino) were processed within 24 h of harvest. The oil mill temperature was controlled (28–30 °C) and the olive paste mixing time was 45 min. The EVOO was extracted via a two-phase decanter (Pieralisi, Italy). The EVOO was placed into 3.7 L (one gallon) dark-green glass jars without headspace, and sent to the food processing laboratory at the University of Florida (Gainesville). Oil samples were stored at −4 °C for further work.
Glove box oxygen levels were measured during and after the packaging using an Oxysense 310 (TMI/Oxysense, Inc. New Castle, DE). This system uses a fluorescent OxyDot, which was mounted to the inside wall of the glove box as well as on the inside wall of the headspace area of clear oil sample containers. The Oxysense 310 was used to measure oxygen levels in volumes containing OxyDots in triplicate.
reduced oxygen headspace packaging of EVOO (Church & Parsons, 1995; Jakobsen & Bertelsen, 2000). Modified atmosphere packaging (MAP) is the removal and/or replacement of the atmosphere surrounding the product within packaging. In passive MAP, package atmospheres are left to change dynamically based upon gas consumption/production by packaged products and permeation characteristics of packaging. Active MAP uses systems to remove and/or replace atmospheres prior to sealing packages. Vacuum and/or gas flush systems are examples of active MAP systems (McMillin, 2008). Since oils are susceptible to oxidation, oil containing foods and oil products tend to benefit from reduced oxygen atmospheres. Typically, reduced oxygen atmospheres are balanced with either nitrogen and/or carbon dioxide, but other gasses are also used sometimes such as Carbon Monoxide (CO), Argon (Ar), and Helium (He) (Fraqueza & Barreto, 2009: McMillin, 2008; Mercogliano et al., 2003). Low oxygen MAP offers opportunity to improve EVOO shelf life. Moreover, control of the storage environment (light and temperature) likely increase the efficiency of MAP on EVOO quality and shelf-life (Jakobsen & Bertelsen, 2000; McMillin, 2008). The aim of this work was to quantify benefits of low oxygen headspace MAP on EVOO for increased shelf-life and enhanced/maintained quality characteristics of EVOO during storage. 2. Materials and methods 2.1. Chemical reagents
2.5. Determination of oil quality indices Free fatty acids (FFA), peroxide value (PV), and extinction coefficients (K232 and K270) of EVOO samples were determined according to the Commission Regulation EU No. 1348/2013 (EU standard methods 1348/2013). The FFA were determined to assess oil molecules or triacylglycerols hydrolysis. Oil (10 g) was dissolved in 80 mL neutralised
2.3. Low oxygen atmospheric packaging experiments EVOO samples (250 mL) were placed in clear or dark (covered by
Fig. 1. Clear and dark (covered by foil) oil containers used in this study. 2
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Fig. 2. Gloves box system (airtight area) used to control the oil headspace oxygen concentration in this study.
using a DU 730 spectrophotometer (Beckman Coulter, DU 730, Lawrence, Life Science UV/VIS, Kansas, USA). Measurements were made in triplicate and expressed as mg/kg oil.
taste ethanol. Two drops of phenolphthalein (1% in ethanol) were added to the solution and titrated with 0.1 N sodium hydroxide (NaOH), previously standardised against hydrochloric acid (HCl). The volume of titrant was recorded and the results expressed as g oleic acid/ 100 g oil. For PV, quantified the chemical products that are produced through reaction with oxygen to ultimately cause oxidative rancidity, oil (5 g) was dissolved in acetic acid / 2, 2, 4-trimethylpentane mixture (3:2). Then, 1 mL of saturated potassium iodide (KI), (70 g KI/40 mL water), was added to solution and shaken for 1 min. Water (70 mL) was added, followed by approx0.5 mL of 1% starch solution (1 g starch/ 100 mL water). The solution was titrated with previously standardised 0.01 N sodium thiosulphate (Na2S2O3). The volume of titrant was recorded and the PV calculated and expressed as milli-equivalents O2/kg oil. Regarding K232 and K270, the presence of conjugated diene and triene systems resulting from oxidation processes, oil (0.25 g) was weighed into a 25 mL volumetric flask and made to volume with cyclohexane. The absorbance of the oil sample was measured on a double beam spectrophotometer, using cyclohexane in 1 cm cell path length, at 232 and 270 nm. All measurements were made in triplicate.
2.8. Determination of oxidative stability index (OSI) Oxidative stability index (OSI) was measured according to Bendini, Gallina Toschi, and Lercker (2001) using a Rancimat 743 apparatus (Metrohm, Switzerland). Olive oil (3 g) was placed in Rancimat standard glass tubes which were subjected to normal operation conditions by heating at 120 °C with an air flow of 20 L/h. The results represent the mean of triplicate samples and expressed as induction period per hour. 2.9. Determination of oil color Oil color was measured according to Chen, Zhu, Zhang, Niu, and Du (2010) by placing olive oil in quartz cuvettes and placing them in the color instrument (Konica Minolta CR 400/410 Chroma Meter, visible spectra 380–770 nm. Tokyo, Japan). The instrument was standardized with a white and black ceramic plate (L0 = 93.01, a0 = -1.11, and b0 = 1.30). The oil color was recorded as L* (lightness), b* (yellowness), and a* (greenness) according to Hunterlab (2001). Based on the Hunter values, threshold values of L*, a*, and b* were defined for the olive oil color. Readings were made in triplicate.
2.6. Determination of total polyphenol compounds Total phenolic compounds were determined by liquid-liquid extraction (three times) from oil dissolved in hexane with methanol/ water (80:20). Total polyphenol concentration was measured using Folin-Ciocalteau reagent according to Gutfinger (1981). Absorption of each sample was read at 725 nm on a spectrophotometer (Beckman Coulter, DU 730, Lawrence, Life Science UV/VIS, Kansas. USA). Standard curves were developed against a gallic acid reference. Measurements were made in triplicate and expressed as mg gallic acid/kg oil.
3. Statistical analysis All experiments were analyzed by ANOVA and Tukey's multiple comparison test (α = 0.05) using SAS (Version 9.0) (Cary, NC, USA). All experiments and analysis were carried out in triplicate.
2.7. Determination of total chlorophyll content
4. Results and discussion
Chlorophyll content was determined according to Isabel MinguezMosquera, Rejano-Navarro, Gandul-Rojas, Sanchez-Gomez, and Garrido-Fernandez (1991). Oil (7.5 g) was dissolved in cyclohexane and the volume was taken to 25 mL. Chlorophyll content was measured at absorbance 670 nm. All absorbance measurements were performed
4.1. Measurement of headspace O2 concentration Headspace oxygen concentrations in EVOO packages were investigated during storage. Fig. 3 shows little variation in headspace oxygen levels during the storage period. The maximum variation 3
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Fig. 3. Variation in O2 concentration at each O2 level in the package headspace during storage. Error bars represent mean ± SD of 3 experiments and 3 readings at each time, n = 9. Different letters indicate statistically significant differences at (p < 0.05).
difference (p < 0.05) between the oil samples, but all package experiments did not exceed the set limit for the “extra virgin” category even after 12 months. The FFA and PV values that were obtained in this study were lower than values reported in several studies for the same package type and storage time (Méndez & Falqué, 2007; Pristouri et al., 2010). Tables 2a and 2b shows a significant difference (p < 0.05) in absorption coefficient (K232 and K270) values for EVOO samples. Results show that K232 values for all EVOO samples were within the set limit (≤ 2.5) (EU Regulation 1989/2003European Communities, 2003EU Regulation 1989/2003) even after 12 months. However, there were no significant differences (p > 0.05) in K232 for all EVOO samples stored with a 2% O2 concentration until 9 months, which means an increase in shelf-life for EVOO up to 3 months compared to other O2 concentrations. Table 2a shows that K270 values were within the set limit (≤ 2.5) (EU Regulation 1989/2003European Communities, 2003EU Regulation 1989/2003) up to 6 months for EVOO samples stored with 21 and 10% O2 concentration at room temperature (25–28 °C) in dark packages and up to 3 months stored in clear packages. While, the K270 values were within the set limit (≤ 2.5) (EU Regulation 1989/2003European Communities, 2003EU Regulation 1989/2003) even after 12 months for EVOO samples stored with 5 and 2% O2 concentrations in both package types. Additionally, Table 2b shows that K270 values were within the set limit (≤ 2.5) (EU Regulation 1989/2003European Communities, 2003EU Regulation 1989/2003) even after 12 months for EVOO samples stored with 10, 5, and 2% O2 concentration at 10 °C in both package types. While, K270 values were within the set limit (≤ 2.5) (EU Regulation 1989/2003European Communities, 2003EU Regulation
of ± 0.9% occurred for all oxygen levels. Changes in headspace oxygen were likely due to oxidative consumption by EVOO during storage. Although there is a minor variation, the rate of O2 consumption by oil during the storage was very low. It might be due to different factors such as using very low O2 concentrations, small headspace volume, and small amount of oil used in this study. These factors might affect the consumption rate of O2 and made it very difficult to be recognized. Due to the limited information available, this data will provide a reference on the low O2 headspace package influence on the consumption rate of O2 in modified atmospheric containers. 4.2. Headspace O2 concentration on quality indices of EVOO Data suggest a significant difference (p < 0.05) in quality indices among all headspace O2 concentrations compared to the normal atmospheric headspace. Results (Table 1a) show that for EVOO stored at 2 and 5% headspace oxygen for both clear and dark packages at room temperature (25–28 °C), FFA and PV were within the set limit of 0.8% and 20 meq O2/kg, respectively (EU Regulation 1989/2003European Communities, 2003EU Regulation 1989/2003) even after 12 months. While the same O2 treated samples stored in clear packages exceeded the FFA and PV limits for "extra virgin" category within 9 and 12 months, respectively. Table 1b shows a significant difference (p < 0.05) in FFA values for EVOO stored at 2 and 5% headspace O2 concentration for clear and dark containers at 10 °C, which did not exceed the limit of “extra virgin” category even after 12 months. While 21 and 10% O2 concentration experiments for both package types exceeded the set limit after 9 months. For PV, data show a significant
Table 1a Changes in FFA and PV of EVOO packaged in dark and clear glass bottles at room temperature (25–28 °C) as a function of headspace O2 concentration and storage time. Values are mean ± SD of 3 replicates and 3 analyses each, n = 9. FFA (%) oleic acid (≤ 0.8)* Month 21% O2 Dark Glass Bottles 0 0.32 ± 0.02a 3 0.42 ± 0.01a 6 0.47 ± 0.04b 9 0.81 ± 0.05c 12 0.92 ± 0.03c Clear Glass Bottles 0 0.32 ± 0.02a 3 0.45 ± 0.01b 6 0.52 ± 0.03b 9 0.84 ± 0.05dc 12 0.99 ± 0.04e
PV (meq O2/kg) (≤ 20)*
10% O2
5% O2
2% O2
21% O2
10% O2
5% O2
2% O2
0.32 0.39 0.44 0.78 0.87
± ± ± ± ±
0.02a 0.02a 0.03ba 0.03c 0.05c
0.32 0.35 0.41 0.74 0.80
± ± ± ± ±
0.02a 0.03a 0.02a 0.05c 0.05c
0.32 0.34 0.40 0.71 0.77
± ± ± ± ±
0.02a 0.02a 0.03a 0.04c 0.02c
6.05 ± 0.4a 9.45 ± 2.3b 11.80 ± 2.1b 14.90 ± 1.9c 17.60 ± 2.6d
6.05 ± 0.4a 9.01 ± 1.8b 11.02 ± 1.9b 14.06 ± 2.0cb 16.94 ± 2.1 cd
6.05 ± 0.4a 8.32 ± 1.6ba 10.35 ± 1.2b 13.19 ± 1.7cb 15.91 ± 1.6 cd
6.05 ± 0.4a 7.90 ± 1.2a 9.40 ± 0.9b 12.84 ± 1.4cb 15.41 ± 1.1 cd
0.32 0.42 0.49 0.82 0.95
± ± ± ± ±
0.02a 0.03ba 0.04b 0.02c 0.05e
0.32 0.39 0.46 0.77 0.81
± ± ± ± ±
0.02a 0.02a 0.03b 0.04c 0.03d
0.32 0.36 0.44 0.75 0.80
± ± ± ± ±
0.02a 0.03a 0.02b 0.05c 0.04d
6.05 ± 0.4a 11.55 ± 2.3cb 14.80 ± 1.9c 18.40 ± 2.0ed 21.80 ± 2.4e
6.05 ± 0.4a 10.43 ± 2.1b 13.51 ± 2.2c 17.01 ± 1.8d 19.05 ± 2.1e
6.05 ± 0.4a 9.40 ± 1.9b 12.60 ± 1.6c 16.03 ± 1.1d 18.02 ± 1.7e
6.05 ± 0.4a 9.05 ± 1.2ba 12.14 ± 0.9c 15.06 ± 1.3d 17.11 ± 1.8e
* European Union Standards (EU Regulation 1989/2003European Communities, 2003EU Regulation 1989/2003) for EVOO. Different letters in same column indicate statistically significant differences (p < 0.05). 4
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Table 1b Changes in FFA and PV of EVOO packaged in dark and clear glass bottles at 10 °C as a function of headspace O2 concentration and storage time. Values are mean ± SD of 3 replicates and 3 analyses each, n = 9. FFA (%) oleic acid (≤ 0.8)* Month 21% O2 Dark Glass Bottles 0 0.32 ± 0.02a 3 0.37 ± 0.01b 6 0.43 ± 0.04c 9 0.76 ± 0.03d 12 0.88 ± 0.04f Clear Glass Bottles 0 0.32 ± 0.02a 3 0.39 ± 0.03b 6 0.45 ± 0.05c 9 0.80 ± 0.04e 12 0.90 ± 0.03f
PV (meq O2/kg) (≤ 20)*
10% O2
5% O2
2% O2
21% O2
10% O2
5% O2
2% O2
0.32 0.34 0.41 0.74 0.84
± ± ± ± ±
0.02a 0.02a 0.03cb 0.05d 0.02f
0.32 0.33 0.37 0.69 0.74
± ± ± ± ±
0.02a 0.02a 0.04b 0.03dc 0.05d
0.32 0.32 0.35 0.65 0.69
± ± ± ± ±
0.02a 0.03a 0.01ba 0.04c 0.04dc
6.05 ± 0.4a 7.95 ± 0.8a 9.60 ± 0.7 10.90 ± 1.3 12.35 ± 1.6
6.05 ± 0.4a 7.40 ± 0.7a 9.0 ± 1.1b 10.55 ± 0.9cb 11.86 ± 1.3c
6.05 ± 0.4a 6.82 ± 0.7a 8.30 ± 0.9ba 9.71 ± 0.7b 10.93 ± 1.4c
6.05 ± 0.4a 6.70 ± 0.5a 7.72 ± 0.6a 9.20 ± 0.5b 10.15 ± 1.2cb
0.32 0.37 0.43 0.78 0.87
± ± ± ± ±
0.02a 0.02a 0.03bc 0.05ed 0.02f
0.32 0.35 0.40 0.74 0.78
± ± ± ± ±
0.02a 0.01a 0.04b 0.03d 0.04ed
0.32 0.34 0.38 0.69 0.73
± ± ± ± ±
0.02a 0.03a 0.03b 0.04d 0.05d
6.05 ± 0.4a 8.85 ± 0.8b 10.55 ± 1.1c 12.91 ± 1.3d 14.85 ± 2.1e
6.05 ± 0.4a 8.25 ± 0.9ba 9.80 ± 0.7b 11.42 ± 1.1c 13.54 ± 1.8ed
6.05 ± 0.4a 7.73 ± 0.6a 8.42 ± 0.8b 10.28 ± 0.9c 12.33 ± 1.6d
6.05 ± 0.4a 7.01 ± 0.4a 8.02 ± 0.5ba 10.11 ± 0.7cb 11.52 ± 1.3c
* European Union Standards (EU Regulation 1989/2003European Communities, 2003EU Regulation 1989/2003) for EVOO. Different letters in same column indicate statistically significant differences (p < 0.05).
for different EVOO samples stored in glass packages (without controlling the headspace) significantly decreased from 519 to 194, 549 to 217, and 433 to 165 (ppm gallic acid) after 3 months storage. Table 3 shows a significant change (p < 0.05) in chlorophylls for EVOO samples in both package types, at both storage temperatures, at different headspace O2 concentrations and storage times. Results show there were no significant differences (p > 0.05) in chlorophyll compounds up to 9 months for the EVOO samples stored with 2% O2 concentration in dark packages at 10 °C. While, 21 and 10% O2 concentration kept the chlorophylls with no significant change (p > 0.05) up to 6 months for EVOO samples stored at 10 °C in dark packages. Moreover, the data for 10, 5, and 2% O2 concentrations in the headspace shows no significant change (p > 0.05) in chlorophylls up to 6 months for EVOO samples stored at room temperature (25–28 °C) in dark packages, while EVOO samples stored at 21% O2 concentration were kept chlorophylls level only up to 3 months. Moreover, results (Table 3) showed that the clear package did not keep the chlorophylls compounds more than 3 months for all headspace O2 concentrations. These results suggest that reducing or controlling oxygen concentration in dark packages during the storage time has a positive effect on chlorophylls compared to the clear package type. In general, EVOO with lower headspace O2 concentrations might be enhancing the concentration of minor compounds during storage and increasing the shelflife of EVOO as well.
1989/2003) up to 9 months for EVOO samples stored with 21% O2 concentration in dark packages and up to 6 months in clear packages. The K232 and K270 values that were obtained in this study were lower than the values reported in several studies for the same package type and storage time (Méndez & Falqué, 2007; Pristouri et al., 2010).
4.3. Headspace O2 concentration on minor compounds Fig. 4 shows a significant change (p < 0.05) in total polyphenols for EVOO samples in both package types, at both storage temperatures, for headspace O2 concentrations and storage time. Results show there were no significant differences (p > 0.05) in total polyphenol levels up to 6 months for EVOO samples stored with 2% O2 concentration in dark packages at 10 °C. While, 5 and 10% O2 concentrations kept the total polyphenol levels up to 3 months (Fig. 4A). In addition, results show there were no significant differences (p > 0.05) in total polyphenol levels up to 3 months for EVOO samples stored with 2 and 5% O2 concentration in clear packages at 10 °C (Fig. 4B). Moreover, the data shows 2% headspace O2 concentrations kept the level of total polyphenols up to 3 months for EVOO samples stored at room temperature (25–28 °C) in dark packages (Fig. 4C), while the EVOO samples stored in clear packages did not keep the level of total polyphenols for more than 3 months (Fig. 4D). These results suggest that reducing or controlling oxygen concentration in the headspace during storage has a positive outcome on total polyphenol compared to previous studies. Méndez and Falqué (2007) who reported that total polyphenol content
Table 2a Changes in absorption coefficients (K232 and K270) of EVOO packaged in dark and clear glass bottles at room temperature (25–28 °C) as a function of headspace O2 concentration and storage time. Values are mean ± SD of 3 replicates and 3 analyses each, n = 9. K232 (≤ 2.5)* Month
10% O2
21% O2
Dark Glass Bottles 0 1.40 ± 3 1.65 ± 6 1.84 ± 9 2.04 ± 12 2.28 ± Clear Glass Bottles 0 1.40 ± 3 1.72 ± 6 1.98 ± 9 2.23 ± 12 2.52 ±
K270 (≤ 0.22)* 5% O2
2% O2
21% O2
10% O2
5% O2
2% O2
0.01a 0.03b 0.03bc 0.05dc 0.05e
1.40 1.58 1.76 1.93 2.09
± ± ± ± ±
0.01a 0.04a 0.05b 0.03c 0.04e
1.40 1.50 1.63 1.75 1.86
± ± ± ± ±
0.01a 0.02a 0.04b 0.05b 0.03bc
1.40 1.45 1.54 1.66 1.75
± ± ± ± ±
0.01a 0.02a 0.03ab 0.02b 0.04b
0.12 0.18 0.22 0.26 0.28
± ± ± ± ±
0.02a 0.03b 0.04c 0.03dc 0.04d
0.12 0.16 0.19 0.22 0.25
± ± ± ± ±
0.02a 0.02b 0.04b 0.05c 0.04c
0.12 0.14 0.16 0.19 0.21
± ± ± ± ±
0.02a 0.03a 0.02b 0.03b 0.02c
0.12 0.14 0.15 0.17 0.19
± ± ± ± ±
0.02a 0.01a 0.03a 0.02b 0.01b
0.01a 0.04b 0.05c 0.03d 0.05d
1.40 1.66 1.89 2.14 2.34
± ± ± ± ±
0.01a 0.05a 0.03b 0.05c 0.06d
1.40 1.57 1.78 1.99 2.16
± ± ± ± ±
0.01a 0.03a 0.05b 0.03c 0.05c
1.40 1.51 1.69 1.86 2.03
± ± ± ± ±
0.01a 0.04a 0.04ba 0.05b 0.03c
0.12 0.21 0.25 0.29 0.32
± ± ± ± ±
0.02a 0.04b 0.03c 0.04d 0.05d
0.12 0.18 0.22 0.24 0.27
± ± ± ± ±
0.02a 0.04b 0.02cb 0.05c 0.05c
0.12 0.15 0.19 0.20 0.22
± ± ± ± ±
0.02a 0.03a 0.03b 0.04b 0.03cb
0.12 0.15 0.18 0.18 0.20
± ± ± ± ±
0.02a 0.04a 0.02b 0.03b 0.02b
* European Union Standards (EU Regulation 1989/2003European Communities, 2003EU Regulation 1989/2003) for EVOO. Different letters in same column indicate statistically significant differences (p < 0.05). 5
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Table 2b Change in absorption coefficients (K232 and K270) of EVOO packaged in dark and clear glass bottles at 10 °C as a function of headspace O2 concentration and storage time. Values are mean ± SD of 3 replicates and 3 analyses each, n = 9. K232 (≤ 2.5)* Month
10% O2
21% O2
Dark Glass Bottles 0 1.40 ± 3 1.60 ± 6 1.78 ± 9 1.95 ± 12 2.19 ± Clear Glass Bottles 0 1.40 ± 3 1.67 ± 6 1.89 ± 9 2.08 ± 12 2.31 ±
K270 (≤ 0.22)* 5% O2
2% O2
± ± ± ± ±
21% O2
10% O2
5% O2
2% O2
0.01a 0.03b 0.04cb 0.02c 0.03d
1.40 1.55 1.73 1.81 2.02
± ± ± ± ±
0.01a 0.02a 0.04b 0.05c 0.04d
1.40 1.46 1.62 1.73 1.86
± ± ± ± ±
0.01a 0.02a 0.03b 0.04b 0.05c
1.40 1.42 1.51 1.64 1.74
0.01a 0.01a 0.02a 0.03b 0.02b
0.12 0.15 0.18 0.21 0.24
± ± ± ± ±
0.02a 0.04b 0.02c 0.03d 0.04d
0.12 0.13 0.15 0.17 0.20
± ± ± ± ±
0.02a 0.01a 0.02b 0.03b 0.02c
0.12 0.12 0.13 0.15 0.18
± ± ± ± ±
0.02a 0.01a 0.03a 0.02b 0.03c
0.12 ± 0.02a 0.12 ± 0.03a 0.13 ± 0.01a 0.15. ± 0.03b 0.16 ± 0.02b
0.01a 0.02b 0.05c 0.03d 0.05f
1.40 1.62 1.82 1.95 2.11
± ± ± ± ±
0.01a 0.04b 0.03c 0.04c 0.04d
1.40 1.57 1.70 1.84 1.95
± ± ± ± ±
0.01a 0.02a 0.04b 0.05c 0.03c
1.40 ± 0.01a 150 ± 0.03a 1.58 ± 0.05a 1.66 ± 0.04b 1.83 ± 0.05c
0.12 0.17 0.21 0.24 0.25
± ± ± ± ±
0.02a 0.03b 0.01c 0.02d 0.03d
0.12 0.15 0.19 0.20 0.22
± ± ± ± ±
0.02a 0.03ba 0.02b 0.03c 0.04c
0.12 0.13 0.15 0.16 0.20
± ± ± ± ±
0.02a 0.02a 0.03ba 0.02b 0.03c
0.12 0.13 0.14 0.15 0.17
± ± ± ± ±
0.02a 0.01a 0.02a 0.01ba 0.02b
* European Union Standards (EU Regulation 1989/2003European Communities, 2003EU Regulation 1989/2003) for EVOO. Different letters in same column indicate statistically significant differences (p < 0.05).
for EVOO samples stored at room temperature (25–28 °C) in both (dark and clear) packages (Fig. 5C) and (Fig. 5D). Because olive oil stability is mainly due to the level of unsaturated fatty acids and antioxidant compounds especially polyphenol compound that has a positive correlation with oxidative stability in virgin olive oil (Baldioli, Servili, Perretti, & Montedoro, 1996: Iqdiam et al., 2019).
4.4. Headspace O2 concentration on oxidative stability index (OSI) Fig. 5 shows a significant change (p < 0.05) in OSI values for EVOO samples packaged in both container types, at both temperatures, as a function of headspace O2 concentrations, and storage time. Results show there were no significant differences (p > 0.05) in OSI values up to 6 months for EVOO samples stored at 2 and 5% O2 concentrations in dark packages at 10 °C storage temperatures. While, 10 and 21% O2 concentrations did not keep the level of OSI for more than 3 months (Fig. 5A). In addition, results show 2 and 5% O2 concentrations kept the OSI constant up to 3 months only for EVOO samples stored at 10 °C in clear package, while the EVOO samples stored with 10 and 21% O2 concentrations did not keep the level of OSI for more than 3 months (Fig. 5B). Low O2 MAP technology did not significantly improve the OSI
4.5. Headspace O2 concentration on EVOO color Tables 4a and 4b shows a significant change (p < 0.05) in EVOO color in both package types, at both storage temperatures, as a function of headspace O2 concentration, and storage time. Table 4a shows there were no significant differences (p > 0.05) in oil color parameters up to 9 months for the EVOO samples stored at 2 and 5% O2 concentrations in
Fig. 4. Changes in total polyphenols (mg/kg) of EVOO samples as a function of headspace O2 concentration and storage time. A) Dark container at 10 °C, B) Clear container at 10 °C, C) Dark container at (25–28 °C), and D) Clear container at (25–28 °C). Error bars represent mean ± SD of 3 experiments and 3 readings at each time, n = 9. Different letters indicate statistically significant differences at (p < 0.05). 6
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Table 3 Changes in Chlorophylls (mg/kg) of EVOO packaged in dark and clear glass bottles at room temperature (25–28 °C) and 10 °C as a function of headspace oxygen concentration and storage time. Values are mean ± SD of 3 replicates and 3 analyses each, n = 9. Room temperature (25 – 28 °C) Month
10% O2
21% O2
Dark Glass Bottles 0 7.10 ± 3 6.72 ± 6 6.31 ± 9 6.03 ± 12 5.81 ± Clear Glass Bottles 0 7.10 ± 3 6.31 ± 6 5.82 ± 9 5.33 ± 12 4.84 ±
Temperature 10 °C 5% O2
2% O2
21% O2
10% O2
5% O2
2% O2
0.45a 0.51b 0.70c 0.41d 0.36d
7.10 6.77 6.42 6.14 5.94
± ± ± ± ±
0.45a 0.35ba 0.48c 0.29c 0.55d
7.10 6.85 6.53 6.26 6.15
± ± ± ± ±
0.45a 0.48a 0.63b 0.44c 0.57c
7.10 6.90 6.58 6.35 6.23
± ± ± ± ±
0.45a 0.55a 0.65b 0.54c 0.71c
7.10 6.83 6.56 6.30 6.07
± ± ± ± ±
0.45a 0.38a 0.47b 0.52cb 0.45b
7.10 6.87 6.64 6.39 6.18
± ± ± ± ±
0.45a 0.62a 0.35b 0.56b 0.43b
7.10 6.98 6.73 6.48 6.29
± ± ± ± ±
0.45a 0.49a 0.52a 0.61b 0.54cb
7.10 7.04 6.82 6.54 6.37
± ± ± ± ±
0.45a 0.5 8a 0.29a 0.53b 0.46b
0.45a 0.72b 0.57c 0.48d 0.73e
7.10 6.35 6.02 5.39 4.95
± ± ± ± ±
0.45a 0.66b 0.44c 0.64d 0.58e
7.10 6.48 6.14 5.47 5.14
± ± ± ± ±
0.45a 0.55b 0.71b 0.62d 0.49ed
7.10 6.52 6.21 5.58 5.27
± ± ± ± ±
0.45a 0.47b 0.65b 0.54c 0.61d
7.10 6.43 6.02 5.73 5.19
± ± ± ± ±
0.45a 0.56b 0.44c 0.53c 062d
7.10 6.54 6.08 5.78 5.26
± ± ± ± ±
0.45a 0.39b 0.55c 0.48c 0.36d
7.10 6.62 6.17 5.85 5.34
± ± ± ± ±
0.45a 0.51b 0.37c 0.55c 0.43d
7.10 6.68 6.25 5.91 5.42
± ± ± ± ±
0.45a 0.72b 0.51b 0.58c 0.49d
Different letters indicate statistically significant differences (p < 0.05).
room temperature (25–28 °C). These results suggest that lower O2 concentration in the headspace during storage has a positive influence on EVOO color compared to previous studies regarding EVOO storage time (Méndez & Falqué, 2007; Pristouri et al., 2010). Generally, packaging EVOO with lower headspace O2 concentrations might help to maintain EVOO color during storage.
dark packages for both storage temperatures. Data shows no significant differences (p > 0.05) in oil color parameters up to 6 months for EVOO samples stored at 10% O2 concentrations in dark packages at 10 °C, while no significant differences (p > 0.05) in oil color parameters up to 3 months occurred for EVOO samples stored at 10% O2 concentrations in dark packages at room temperature (25–28 °C). Additionally, Table 4b shows there were no significant differences (p > 0.05) in oil color parameters up to 6 months for EVOO samples stored at 2 and 5% O2 concentrations in clear packages for both storage temperatures. Data shows no significant differences (p > 0.05) in oil color parameters up to 3 months for EVOO samples stored with 10% O2 concentrations in clear packages at both storage temperatures while no significant differences (p > 0.05) in oil color parameters resulted up to 3 months for EVOO samples stored at 10% O2 concentrations in dark packages at
5. Conclusion Low headspace oxygen concentration is important for maintaining quality and shelf-life of EVOO. Based upon data presented here, the following conclusions may be drawn: (a) EVOO at 2 and 5% headspace oxygen, in glass containers (clear or dark), at room temperature and 10 °C protects chemical indices of EVOO beyond 12 months; (b) EVOO
Fig. 5. Changes in OSI (induction time h.) of EVOO samples as a function of headspace O2 concentration and storage time. A) Dark container at 10 °C, B) Clear container at 10 °C, C) Dark container at (25–28 °C), and D) Clear container at (25–28 °C). Error bars represent mean ± SD of 3 experiments and 3 readings at each time, n = 9. Different letters indicate statistically significant differences at (p < 0.05). 7
21% O2
± ± ± ± ± ± ± ± ± ± ± ± ± ± ±
0.30a 0.05a 0.15a 0.62a 0.03b 0.24b 0.30b 0.02c 0.32cb 0.62c 0.05c 0.38c 0.37c 0.02d 0.40d
L = 80.25 a = -0.38 b = 78.62 L = 79.16 a = -0.40 b = 77.42 L = 77.96 a = -0.44 b = 76.25 L = 75.39 a = -0.45 b = 74.15 L = 74.75 a = -0.47 b = 72.83
10% O2
± ± ± ± ± ± ± ± ± ± ± ± ± ± ±
0.30a 0.05a 0.15a 0.27a 0.02a 0.55a 0.55b 0.05b 0.60b 0.30cb 0.04c 0.62c 0.68c 0.03c 0.32c
L = 80.25 a = -0.38 b = 78.62 L = 80.08 a = -0.39 b = 78.44 L = 78.73 a = -0.41 b = 77.45 L = 76.81 a = -0.43 b = 76.18 L = 75.37 a = -0.45 b = 74.35
5% O2
± ± ± ± ± ± ± ± ± ± ± ± ± ± ±
0.30a 0.05a 0.15a 0.18a 0.01a 0.26a 0.59a 0.03ba 0.35a 0.62b 0.03b 0.45b 0.40cb 0.05c 0.28c
L = 80.25 a = -0.38 b = 78.62 L = 80.14 a = -0.38 b = 78.54 L = 79.24 a = -0.40 b = 77.85 L = 77.60 a = -0.42 b = 76.88 L = 76.81 a = -0.44 b = 75.65
2% O2
± ± ± ± ± ± ± ± ± ± ± ± ± ± ±
0.30a 0.05a 0.15a 0.27a 0.02a 0.64a 0.25a 0.02a 0.66a 0.38b 0.02ba 0.25b 0.60b 0.04cb 0.32cb
L = 80.25 a = -0.38 b = 78.62 L = 79.69 a = -0.40 b = 77.45 L = 77.24 a = -0.42 b = 76.15 L = 75.83 a = -0.45 b = 74.58 L = 74.22 a = -0.46 b = 72.19
21% O2
± ± ± ± ± ± ± ± ± ± ± ± ± ± ±
0.30a 0.05a 0.15a 0.51a 0.02a 0.38a 0.36b 0.04b 0.75b 0.27c 0.03c 0.42c 0.55c 0.03c 0.30d
Temperature 10 °C
L = 80.25 a = -0.38 b = 78.62 L = 80.01 a = -0.39 b = 77.93 L = 77.92 a = -0.40 b = 76.85 L = 76.48 a = -0.44 b = 75.28 L = 75.65 a = -0.45 b = 74.50
10% O2
± ± ± ± ± ± ± ± ± ± ± ± ± ± ±
0.30a 0.05a 0.15a 0.72a 0.04a 0.52a 0.52b 0.03a 0.48ba 0.36cb 0.04c 0.61cb 0.28c 0.02c 0.62c
L = 80.25 a = -0.38 b = 78.62 L = 80.12 a = -0.38 b = 78.27 L = 78.81 a = -0.39 b = 77.55 L = 78.08 a = -0.41 b = 76.55 L = 76.22 a = -0.43 b = 75.34
5% O2
± ± ± ± ± ± ± ± ± ± ± ± ± ± ±
0.30a 0.05a 0.15a 0.19a 0.03a 0.58a 0.27ba 0.04a 0.40a 0.25b 0.03ba 0.42b 0.37cb 0.05b 0.28c
L = 80.25 a = -0.38 b = 78.62 L = 80.18 a = -0.38 b = 78.48 L = 79.25 a = -0.39 b = 77.81 L = 78.92 a = -0.40 b = 76.96 L = 77.45 a = -0.41 b = 75.94
2% O2
± ± ± ± ± ± ± ± ± ± ± ± ± ± ±
0.30a 0.05a 0.15a 0.22a 0.05a 0.11a 0.62a 0.03a 0.50a 0.45ba 0.05a 0.40b 0.42b 0.02ba 0.50c
8
21% O2
± ± ± ± ± ± ± ± ± ± ± ± ± ± ±
0.30a 0.05a 0.15a 0.62ba 0.02b 0.33b 0.35cb 0.05b 0.58c 0.25c 0.03c 0.41c 0.32d 0.02d 0.54c
L = 80.25 a = -0.38 b = 78.62 L = 78.02 a = -0.42 b = 76.11 L = 75.82 a = -0.45 b = 74.19 L = 73.58 a = -0.47 b = 72.15 L = 70.40 a = -0.48 b = 71.31
10% O2
± ± ± ± ± ± ± ± ± ± ± ± ± ± ±
0.30a 0.05a 0.15a 0.45a 0.03a 0.20a 0.42b 0.02b 0.27b 0.35c 0.05b 0.30c 0.59dc 0.04c 0.27c
L = 80.25 a = -0.38 b = 78.62 L = 79.64 a = -0.41 b = 77.25 L = 77.18 a = -0.42 b = 76.73 L = 75.26 a = -0.44 b = 74.11 L = 73.48 a = -0.45 b = 73.38
5% O2
Different letters indicate statistically significant differences (p < 0.05).
Clear Glass Bottles 0 L = 80.25 a = -0.38 b = 78.62 3 L = 77.08 a = -0.44 b = 74.11 6 L = 74.22 a = -0.47 b = 72.44 9 L = 71.18 a = -0.49 b = 70.44 12 L = 68.20 a = -0.51 b = 69.34
Month
Room temperature (25 – 28 °C)
± ± ± ± ± ± ± ± ± ± ± ± ± ± ±
0.30a 0.05a 0.15a 0.48a 0.04a 0.35a 0.27ba 0.04a 0.38a 0.64b 0.02b 0.33b 0.36c 0.03b 0.46b
L = 80.25 a = -0.38 b = 78.62 L = 79.70 a = -0.40 b = 77.61 L = 78.31 a = -0.42 b = 76.91 L = 76.18 a = -0.43 b = 75.71 L = 75.25 a = -0.44 b = 74.42
2% O2
± ± ± ± ± ± ± ± ± ± ± ± ± ± ±
0.30a 0.05a 0.15a 0.36a 0.03a 0.60a 0.55a 0.02a 0.63a 0.44b 0.03a 0.55b 0.35b 0.02b 0.55b
L = 80.25 ± 0.30a a = -0.38 ± 0.05a b = 78.62 ± 0.15a L = 78.20 ± 0.52a a = -0.43 ± 0.02b b = 76.3 ± 0.47a L = 75.88 ± 0.70b a = -0.45 ± 0.03b b = 74.38 ± 0.25b L = 73.10 ± 0.22c a = -0.47 ± 0.04c b = 72.68 ± 0.20c L = 71.55 ± 0.42d a = -0.49 ± 0.03d b = 70.65 ± 0.47d
21% O2
Temperature 10 °C
L = 80.25 a = -0.38 b = 78.62 L = 79.50 a = -0.41 b = 77.27 L = 76.44 a = -0.43 b = 75.58 L = 74.45 a = -0.45 b = 74.35 L = 73.25 a = -0.47 b = 72.33
10% O2
± ± ± ± ± ± ± ± ± ± ± ± ± ± ±
0.30a 0.05a 0.15a 0.39a 0.04a 0.28a 0.50b 0.04b 0.25b 0.31c 0.03b 0.20b 0.55c 0.04c 0.28c
L = 80.25 a = -0.38 b = 78.62 L = 79.05 a = -0.40 b = 78.12 L = 77.25 a = -0.42 b = 76.48 L = 75.82 a = -0.43 b = 75.35 L = 74.48 a = -0.45 b = 73.85
5% O2
± ± ± ± ± ± ± ± ± ± ± ± ± ± ±
0.30a 0.05a 0.15a 0.20a 0.03a 0.24a 0.50ba 0.03ba 0.25a 0.50cb 0.04b 0.45b 0.29c 0.01b 0.52cb
L = 80.25 a = -0.38 b = 78.62 L = 79.63 a = -0.40 b = 78.36 L = 77.45 a = -0.42 b = 77.19 L = 76.55 a = -0.43 b = 76.61 L = 75.80 a = -0.44 b = 75.20
2% O2
± ± ± ± ± ± ± ± ± ± ± ± ± ± ±
0.30a 0.05a 0.15a 0.32a 0.02a 0.17a 0.30ba 0.01ba 0.24a 0.28b 0.02b 0.25a 0.36b 0.04b 0.18b
Table 4b Changes in color of EVOO packaged in clear glass bottles at room temperature (25–28 °C) and 10 °C as a function of headspace oxygen concentration and storage time. Values are mean ± SD of 3 replicates and 3 analyses each, n = 9.
Different letters indicate statistically significant differences (p < 0.05).
Dark Glass Bottles 0 L = 80.25 a = -0.38 b = 78.62 3 L = 78.31 a = -0.42 b = 76.11 6 L = 76.75 a = -0.46 b = 74.41 9 L = 74.20 a = -0.47 b = 72.17 12 L = 73.28 a = -0.49 b = 70.25
Month
Room temperature (25 – 28 °C)
Table 4a Changes in color of EVOO packaged in dark glass bottles at room temperature (25–28 °C) and 10 °C as a function of headspace oxygen concentration and storage time. Values are mean ± SD of 3 replicates and 3 analyses each, n = 9.
B.M. Iqdiam, et al.
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with 2% headspace oxygen in dark bottles at 10 °C protects total polyphenols of EVOO beyond 6 months; (c) EVOO with 2 and 5% headspace oxygen in dark bottles at 10 °C protects chlorophylls of EVOO beyond 6 months; (d) EVOO with 2% oxygen headspace, in dark glass containers at 10 °C protects the OSI of EVOO beyond 6 months; and (e) EVOO with 2 and 5% headspace oxygen in dark bottles at 10 °C protects color parameters of EVOO beyond 9 months. Overall, low oxygen MAP technology appears viable for enhancing the shelf-life of EVOO during storage. Understanding how MAP technology influences EVOO quality and shelf-life will ultimately assist processors in improving the storage conditions for EVOO. Combining MAP technology and other factors such as packaging type, package headspace volume, and storage temperature are likely to present potential advantages for EVOO storage.
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Acknowledgements We wish to thank the Clear Creek Olive Company in Ocala, Florida for helping to supply the extra virgin olive oil used in this study. This research was supported by the Florida Agricultural Experiment Station. References Bajoub, A. (2016). Virgin olive oil: Potential of different omics approaches to authenticate its geographical and botanical origin (Doctoral dissertation). Universidad de Granada. Bendini, A., Gallina Toschi, T., & Lercker, G. (2001). Determinazione dell’attività antiossidante di estratti vegetali mediante Oxidative Stability Instrument (OSI). Industrie Alimentari, 40, 525. Baldioli, M., Servili, M., Perretti, G., & Montedoro, G. F. (1996). Antioxidant activity of tocopherols and phenolic compounds of virgin olive oil. Journal of the American Oil Chemists’ Society, 73(11), 1589–1593. Caponio, F., Bilancia, M. T., Pasqualone, A., Sikorska, E., & Gomes, T. (2005). Influence of the exposure to light on extra virgin olive oil quality during storage. European Food Research and Technology, 221(1-2), 92–98. Calvo, P., Castaño, A. L., Lozano, M., & González-Gómez, D. (2012). Influence of the microencapsulation on the quality parameters and shelf-life of extra-virgin olive oil encapsulated in the presence of BHT and different capsule wall components. Food Research International, 45(1), 256–261. Cecchi, T., Passamonti, P., & Cecchi, P. (2010). Study of the quality of extra virgin olive oil stored in PET bottles with or without an oxygen scavenger. Food Chemistry, 120(3), 730–735. Cosio, M. S., Ballabio, D., Benedetti, S., & Gigliotti, C. (2007). Evaluation of different storage conditions of extra virgin olive oils with an innovative recognition tool built by means of electronic nose and electronic tongue. Food Chemistry, 101(2), 485–491. Chen, Z., Zhu, C., Zhang, Y., Niu, D., & Du, J. (2010). Postharvest Biology and Technology Effects of aqueous chlorine dioxide treatment on enzymatic browning and shelf-life of fresh-cut asparagus lettuce (Lactuca sativa L.). Postharvest Biology and Technology, 58(3), 232–238.
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Food Packaging and Shelf Life journal homepage: www.elsevier.com/locate/fpsl
Influence of headspace oxygen on quality and shelf life of extra virgin olive oil during storage
T
Basheer M. Iqdiama, Bruce A Weltb,*, Renee Goodrich-Schneidera, Charles A Simsa, George L. Baker IVa, Maurice R. Marshalla a b
Food Science and Human Nutrition Department, University of Florida, Gainesville, FL 32611, United States Agricultural & Biological Engineering Department, University of Florida, Gainesville, FL 32611, United States
A R T I C LE I N FO
A B S T R A C T
Keywords: Extra virgin olive oil Modified atmosphere packaging Shelf life Oxygen Quality
This study evaluated the impact of low O2 headspace in clear and dark containers at different storage temperatures (10 °C and 28 °C) on the quality and shelf life of extra virgin olive oil (EVOO). Bottle headspace was controlled at four different O2 concentrations 2, 5, 10, and 21%. Quality parameters were determined after 3, 6, 9, and 12 months storage: free fatty acids, peroxide value, absorption coefficients K270 and K230, total polyphenols, chlorophyll content, oxidative stability index, and color. Results show low headspace oxygen levels of 2 and 5%, significantly increased EVOO shelf life stored in dark and clear bottles at 10 °C. While the improvement in EVOO shelf-life was less when stored at 28 °C. No significant differences occurred between EVOO samples packaged at 10 and 21% headspace O2 concentrations in clear bottles stored at 28 °C while significant differences were observed with 2 and 5% headspace O2 concentrations. These results suggest that it is important to minimize headspace oxygen in packages of extra virgin olive oil.
1. Introduction Extra virgin olive oil (EVOO) may have nutritional, therapeutic, and gastronomic benefits compared with other olive oil categories (Bajoub, 2016; Calvo, Castaño, Lozano, & González-Gómez, 2012; Caponio, Bilancia, Pasqualone, Sikorska, & Gomes, 2005; Frankel, 2010; LermaGarcía et al., 2009; Romani et al., 2007). Chemically, EVOO may be the best olive oil for its organoleptic characteristics, stability and chemical composition. EVOO is the oil of the olive fruit that is picked at optimum maturity index and correctly processed. EVOO is the only vegetable oil that can be consumed directly in its raw state and contains important nutritional elements (European Communities, 1991; International Olive Oil Council, 1996). The unique characteristics of EVOO are sufficiently valuable to warrant special care in packaging and storage. Proper packaging is critical to preserve nutrition, flavor and color attributes of EVOO (Caponio et al., 2005; Cecchi, Passamonti, & Cecchi, 2010; Romani et al., 2007). The quality and shelf-life of edible oil is limited by oxidation, and this constitutes a major factor for quality deterioration of EVOO during storage (Frankel, 2010, 2014; Nobile, Ambrosino, Sacchi, & Masi, 2003; Parenti, Spugnoli, Masella, & Calamai, 2007; Pristouri, Badeka, & Kontominas, 2010). Oxidation causes oil to become rancid and
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unsuitable for human consumption (Morales & Przybylski, 2013). Light, temperature, headspace oxygen, natural antioxidant content, and the oxygen dissolved in EVOO when bottled are factors that most influence on the level of oxidation during storage. Moreover, oxygen concentration in the oil prior to packaging, initial headspace oxygen partial pressure, oxygen permeability through packaging are important factors influencing deterioration of lipids and overall EVOO quality and shelflife during storage (Del Nobile, Bove, La Notte, & Sacchi, 2003; Parenti et al., 2007; Pristouri et al., 2010). Dark containers, optimal package oxygen barrier properties, and low temperatures during storage are helpful in preserving EVOO quality (Caponio et al., 2005; Cecchi et al., 2010; Cosio, Ballabio, Benedetti, & Gigliotti, 2007; Pristouri et al., 2010). Most previous studies have focused on the type of packaging materials, light transmission, temperature, and time of storage on quality, sensory attributes, and shelf-life of EVOO (Calvo et al., 2012; Caponio et al., 2005; Cecchi et al., 2010; Méndez & Falqué, 2007; Pristouri et al., 2010). While there is an absence of information on how reducing or controlling the O2 headspace concentration in the package influences quality, shelf-life, and preferred sensory characteristics of EVOO. Due to the gap in information concerning the optimum package headspace O2 concentration during storage, additional research is needed to quantify potential benefits of
Corresponding author at: Department of Agricultural and Biological Engineering, 229 Frazier Rogers Hall, PO Box 110570 Gainesville, FL 32611, United States. E-mail address: bwelt@ufl.edu (B.A. Welt).
https://doi.org/10.1016/j.fpsl.2019.100433 Received 18 December 2018; Received in revised form 17 October 2019; Accepted 28 October 2019 2214-2894/ © 2019 Elsevier Ltd. All rights reserved.
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Ethanol, diethyl ether (pro analysis grade), sodium thiosulphate, potassium iodine, sodium hydroxide, acetic acid, chloroform, and cyclohexane for the determination of the free fatty acids (FFA), peroxide value (PV), and absorption coefficients (K232, K270) were purchased from Fisher Scientific (Fisher Scientific, MO, USA).
foil) glass jars (300 mL) purchased from Fischer Scientific (Fisher Scientific, MO, USA) and hermetically sealed (Fig. 1). The preferred barrier properties of the glass material and the accuracy of sealed were the major factors of selecting the type of jar. Jar has a neck having an in-turned flange at its upper end and two vertically spaced, horizontal inward-formed beads with two outward-downward conical surfaces above and below the lower inward-formed beads. The vacuum seal cap of the jar contains a plastic lid that keeps it airtight. The cap has a top disk with a depending short inner skirt having a tapered edge and an elongated peripheral skirt. The in-turned flange of the neck is compressed between the two cap skirts, the upper internal bead seats against the upper conical surface and the locking bead seats in the lower inward-formed bead of the neck. Thus a product and air-tight multi-zone seal is effected; and, further, once seated the cap is tamperproof in that it must be opened or tear to be removed. Headspace volumes were 50 mL after placing the oil in jars. Jars were placed in a hermetically sealed glove box (Fig. 2). Four different oxygen concentrations were applied to the oil samples 21% oxygen (control/ normal atmosphere pressure); and 10% oxygen; 5% oxygen; and 2% oxygen (at atmosphere pressure). The glove box was equipped with inlet and outlet gas valves that were used to modify the atmosphere within the glove box. A gas mixer (Multi-Component Gas Mixing System Series 4000, Environics, Inc. CT, USA) was used with compressed are and nitrogen sourced from the gas port of a liquid nitrogen cryogenic dewar. Glove box outlet gas was discharged through water placed in a glass beaker to avoid atmospheric air flowing backward into the glove box when changing gas bottles or dewars. After achieving desired oxygen concentrations within the glove box, oil containers were sealed within the glove box. Samples in clear and dark containers were removed and stored at two different temperatures: room temperature (25–28 °C) and in an environmental chamber set to 10 °C for 3, 6, 9, and 12 months.
2.2. Olive oil samples
2.4. Headspace oxygen concentration measurement
EVOO was obtained from a local mill in Ocala, FL (crop season 2017), and its quality characteristics at the beginning of the study are identified. Olives of different cultivars (Arbequina, Koroneiki, and Leccino) were processed within 24 h of harvest. The oil mill temperature was controlled (28–30 °C) and the olive paste mixing time was 45 min. The EVOO was extracted via a two-phase decanter (Pieralisi, Italy). The EVOO was placed into 3.7 L (one gallon) dark-green glass jars without headspace, and sent to the food processing laboratory at the University of Florida (Gainesville). Oil samples were stored at −4 °C for further work.
Glove box oxygen levels were measured during and after the packaging using an Oxysense 310 (TMI/Oxysense, Inc. New Castle, DE). This system uses a fluorescent OxyDot, which was mounted to the inside wall of the glove box as well as on the inside wall of the headspace area of clear oil sample containers. The Oxysense 310 was used to measure oxygen levels in volumes containing OxyDots in triplicate.
reduced oxygen headspace packaging of EVOO (Church & Parsons, 1995; Jakobsen & Bertelsen, 2000). Modified atmosphere packaging (MAP) is the removal and/or replacement of the atmosphere surrounding the product within packaging. In passive MAP, package atmospheres are left to change dynamically based upon gas consumption/production by packaged products and permeation characteristics of packaging. Active MAP uses systems to remove and/or replace atmospheres prior to sealing packages. Vacuum and/or gas flush systems are examples of active MAP systems (McMillin, 2008). Since oils are susceptible to oxidation, oil containing foods and oil products tend to benefit from reduced oxygen atmospheres. Typically, reduced oxygen atmospheres are balanced with either nitrogen and/or carbon dioxide, but other gasses are also used sometimes such as Carbon Monoxide (CO), Argon (Ar), and Helium (He) (Fraqueza & Barreto, 2009: McMillin, 2008; Mercogliano et al., 2003). Low oxygen MAP offers opportunity to improve EVOO shelf life. Moreover, control of the storage environment (light and temperature) likely increase the efficiency of MAP on EVOO quality and shelf-life (Jakobsen & Bertelsen, 2000; McMillin, 2008). The aim of this work was to quantify benefits of low oxygen headspace MAP on EVOO for increased shelf-life and enhanced/maintained quality characteristics of EVOO during storage. 2. Materials and methods 2.1. Chemical reagents
2.5. Determination of oil quality indices Free fatty acids (FFA), peroxide value (PV), and extinction coefficients (K232 and K270) of EVOO samples were determined according to the Commission Regulation EU No. 1348/2013 (EU standard methods 1348/2013). The FFA were determined to assess oil molecules or triacylglycerols hydrolysis. Oil (10 g) was dissolved in 80 mL neutralised
2.3. Low oxygen atmospheric packaging experiments EVOO samples (250 mL) were placed in clear or dark (covered by
Fig. 1. Clear and dark (covered by foil) oil containers used in this study. 2
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Fig. 2. Gloves box system (airtight area) used to control the oil headspace oxygen concentration in this study.
using a DU 730 spectrophotometer (Beckman Coulter, DU 730, Lawrence, Life Science UV/VIS, Kansas, USA). Measurements were made in triplicate and expressed as mg/kg oil.
taste ethanol. Two drops of phenolphthalein (1% in ethanol) were added to the solution and titrated with 0.1 N sodium hydroxide (NaOH), previously standardised against hydrochloric acid (HCl). The volume of titrant was recorded and the results expressed as g oleic acid/ 100 g oil. For PV, quantified the chemical products that are produced through reaction with oxygen to ultimately cause oxidative rancidity, oil (5 g) was dissolved in acetic acid / 2, 2, 4-trimethylpentane mixture (3:2). Then, 1 mL of saturated potassium iodide (KI), (70 g KI/40 mL water), was added to solution and shaken for 1 min. Water (70 mL) was added, followed by approx0.5 mL of 1% starch solution (1 g starch/ 100 mL water). The solution was titrated with previously standardised 0.01 N sodium thiosulphate (Na2S2O3). The volume of titrant was recorded and the PV calculated and expressed as milli-equivalents O2/kg oil. Regarding K232 and K270, the presence of conjugated diene and triene systems resulting from oxidation processes, oil (0.25 g) was weighed into a 25 mL volumetric flask and made to volume with cyclohexane. The absorbance of the oil sample was measured on a double beam spectrophotometer, using cyclohexane in 1 cm cell path length, at 232 and 270 nm. All measurements were made in triplicate.
2.8. Determination of oxidative stability index (OSI) Oxidative stability index (OSI) was measured according to Bendini, Gallina Toschi, and Lercker (2001) using a Rancimat 743 apparatus (Metrohm, Switzerland). Olive oil (3 g) was placed in Rancimat standard glass tubes which were subjected to normal operation conditions by heating at 120 °C with an air flow of 20 L/h. The results represent the mean of triplicate samples and expressed as induction period per hour. 2.9. Determination of oil color Oil color was measured according to Chen, Zhu, Zhang, Niu, and Du (2010) by placing olive oil in quartz cuvettes and placing them in the color instrument (Konica Minolta CR 400/410 Chroma Meter, visible spectra 380–770 nm. Tokyo, Japan). The instrument was standardized with a white and black ceramic plate (L0 = 93.01, a0 = -1.11, and b0 = 1.30). The oil color was recorded as L* (lightness), b* (yellowness), and a* (greenness) according to Hunterlab (2001). Based on the Hunter values, threshold values of L*, a*, and b* were defined for the olive oil color. Readings were made in triplicate.
2.6. Determination of total polyphenol compounds Total phenolic compounds were determined by liquid-liquid extraction (three times) from oil dissolved in hexane with methanol/ water (80:20). Total polyphenol concentration was measured using Folin-Ciocalteau reagent according to Gutfinger (1981). Absorption of each sample was read at 725 nm on a spectrophotometer (Beckman Coulter, DU 730, Lawrence, Life Science UV/VIS, Kansas. USA). Standard curves were developed against a gallic acid reference. Measurements were made in triplicate and expressed as mg gallic acid/kg oil.
3. Statistical analysis All experiments were analyzed by ANOVA and Tukey's multiple comparison test (α = 0.05) using SAS (Version 9.0) (Cary, NC, USA). All experiments and analysis were carried out in triplicate.
2.7. Determination of total chlorophyll content
4. Results and discussion
Chlorophyll content was determined according to Isabel MinguezMosquera, Rejano-Navarro, Gandul-Rojas, Sanchez-Gomez, and Garrido-Fernandez (1991). Oil (7.5 g) was dissolved in cyclohexane and the volume was taken to 25 mL. Chlorophyll content was measured at absorbance 670 nm. All absorbance measurements were performed
4.1. Measurement of headspace O2 concentration Headspace oxygen concentrations in EVOO packages were investigated during storage. Fig. 3 shows little variation in headspace oxygen levels during the storage period. The maximum variation 3
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Fig. 3. Variation in O2 concentration at each O2 level in the package headspace during storage. Error bars represent mean ± SD of 3 experiments and 3 readings at each time, n = 9. Different letters indicate statistically significant differences at (p < 0.05).
difference (p < 0.05) between the oil samples, but all package experiments did not exceed the set limit for the “extra virgin” category even after 12 months. The FFA and PV values that were obtained in this study were lower than values reported in several studies for the same package type and storage time (Méndez & Falqué, 2007; Pristouri et al., 2010). Tables 2a and 2b shows a significant difference (p < 0.05) in absorption coefficient (K232 and K270) values for EVOO samples. Results show that K232 values for all EVOO samples were within the set limit (≤ 2.5) (EU Regulation 1989/2003European Communities, 2003EU Regulation 1989/2003) even after 12 months. However, there were no significant differences (p > 0.05) in K232 for all EVOO samples stored with a 2% O2 concentration until 9 months, which means an increase in shelf-life for EVOO up to 3 months compared to other O2 concentrations. Table 2a shows that K270 values were within the set limit (≤ 2.5) (EU Regulation 1989/2003European Communities, 2003EU Regulation 1989/2003) up to 6 months for EVOO samples stored with 21 and 10% O2 concentration at room temperature (25–28 °C) in dark packages and up to 3 months stored in clear packages. While, the K270 values were within the set limit (≤ 2.5) (EU Regulation 1989/2003European Communities, 2003EU Regulation 1989/2003) even after 12 months for EVOO samples stored with 5 and 2% O2 concentrations in both package types. Additionally, Table 2b shows that K270 values were within the set limit (≤ 2.5) (EU Regulation 1989/2003European Communities, 2003EU Regulation 1989/2003) even after 12 months for EVOO samples stored with 10, 5, and 2% O2 concentration at 10 °C in both package types. While, K270 values were within the set limit (≤ 2.5) (EU Regulation 1989/2003European Communities, 2003EU Regulation
of ± 0.9% occurred for all oxygen levels. Changes in headspace oxygen were likely due to oxidative consumption by EVOO during storage. Although there is a minor variation, the rate of O2 consumption by oil during the storage was very low. It might be due to different factors such as using very low O2 concentrations, small headspace volume, and small amount of oil used in this study. These factors might affect the consumption rate of O2 and made it very difficult to be recognized. Due to the limited information available, this data will provide a reference on the low O2 headspace package influence on the consumption rate of O2 in modified atmospheric containers. 4.2. Headspace O2 concentration on quality indices of EVOO Data suggest a significant difference (p < 0.05) in quality indices among all headspace O2 concentrations compared to the normal atmospheric headspace. Results (Table 1a) show that for EVOO stored at 2 and 5% headspace oxygen for both clear and dark packages at room temperature (25–28 °C), FFA and PV were within the set limit of 0.8% and 20 meq O2/kg, respectively (EU Regulation 1989/2003European Communities, 2003EU Regulation 1989/2003) even after 12 months. While the same O2 treated samples stored in clear packages exceeded the FFA and PV limits for "extra virgin" category within 9 and 12 months, respectively. Table 1b shows a significant difference (p < 0.05) in FFA values for EVOO stored at 2 and 5% headspace O2 concentration for clear and dark containers at 10 °C, which did not exceed the limit of “extra virgin” category even after 12 months. While 21 and 10% O2 concentration experiments for both package types exceeded the set limit after 9 months. For PV, data show a significant
Table 1a Changes in FFA and PV of EVOO packaged in dark and clear glass bottles at room temperature (25–28 °C) as a function of headspace O2 concentration and storage time. Values are mean ± SD of 3 replicates and 3 analyses each, n = 9. FFA (%) oleic acid (≤ 0.8)* Month 21% O2 Dark Glass Bottles 0 0.32 ± 0.02a 3 0.42 ± 0.01a 6 0.47 ± 0.04b 9 0.81 ± 0.05c 12 0.92 ± 0.03c Clear Glass Bottles 0 0.32 ± 0.02a 3 0.45 ± 0.01b 6 0.52 ± 0.03b 9 0.84 ± 0.05dc 12 0.99 ± 0.04e
PV (meq O2/kg) (≤ 20)*
10% O2
5% O2
2% O2
21% O2
10% O2
5% O2
2% O2
0.32 0.39 0.44 0.78 0.87
± ± ± ± ±
0.02a 0.02a 0.03ba 0.03c 0.05c
0.32 0.35 0.41 0.74 0.80
± ± ± ± ±
0.02a 0.03a 0.02a 0.05c 0.05c
0.32 0.34 0.40 0.71 0.77
± ± ± ± ±
0.02a 0.02a 0.03a 0.04c 0.02c
6.05 ± 0.4a 9.45 ± 2.3b 11.80 ± 2.1b 14.90 ± 1.9c 17.60 ± 2.6d
6.05 ± 0.4a 9.01 ± 1.8b 11.02 ± 1.9b 14.06 ± 2.0cb 16.94 ± 2.1 cd
6.05 ± 0.4a 8.32 ± 1.6ba 10.35 ± 1.2b 13.19 ± 1.7cb 15.91 ± 1.6 cd
6.05 ± 0.4a 7.90 ± 1.2a 9.40 ± 0.9b 12.84 ± 1.4cb 15.41 ± 1.1 cd
0.32 0.42 0.49 0.82 0.95
± ± ± ± ±
0.02a 0.03ba 0.04b 0.02c 0.05e
0.32 0.39 0.46 0.77 0.81
± ± ± ± ±
0.02a 0.02a 0.03b 0.04c 0.03d
0.32 0.36 0.44 0.75 0.80
± ± ± ± ±
0.02a 0.03a 0.02b 0.05c 0.04d
6.05 ± 0.4a 11.55 ± 2.3cb 14.80 ± 1.9c 18.40 ± 2.0ed 21.80 ± 2.4e
6.05 ± 0.4a 10.43 ± 2.1b 13.51 ± 2.2c 17.01 ± 1.8d 19.05 ± 2.1e
6.05 ± 0.4a 9.40 ± 1.9b 12.60 ± 1.6c 16.03 ± 1.1d 18.02 ± 1.7e
6.05 ± 0.4a 9.05 ± 1.2ba 12.14 ± 0.9c 15.06 ± 1.3d 17.11 ± 1.8e
* European Union Standards (EU Regulation 1989/2003European Communities, 2003EU Regulation 1989/2003) for EVOO. Different letters in same column indicate statistically significant differences (p < 0.05). 4
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Table 1b Changes in FFA and PV of EVOO packaged in dark and clear glass bottles at 10 °C as a function of headspace O2 concentration and storage time. Values are mean ± SD of 3 replicates and 3 analyses each, n = 9. FFA (%) oleic acid (≤ 0.8)* Month 21% O2 Dark Glass Bottles 0 0.32 ± 0.02a 3 0.37 ± 0.01b 6 0.43 ± 0.04c 9 0.76 ± 0.03d 12 0.88 ± 0.04f Clear Glass Bottles 0 0.32 ± 0.02a 3 0.39 ± 0.03b 6 0.45 ± 0.05c 9 0.80 ± 0.04e 12 0.90 ± 0.03f
PV (meq O2/kg) (≤ 20)*
10% O2
5% O2
2% O2
21% O2
10% O2
5% O2
2% O2
0.32 0.34 0.41 0.74 0.84
± ± ± ± ±
0.02a 0.02a 0.03cb 0.05d 0.02f
0.32 0.33 0.37 0.69 0.74
± ± ± ± ±
0.02a 0.02a 0.04b 0.03dc 0.05d
0.32 0.32 0.35 0.65 0.69
± ± ± ± ±
0.02a 0.03a 0.01ba 0.04c 0.04dc
6.05 ± 0.4a 7.95 ± 0.8a 9.60 ± 0.7 10.90 ± 1.3 12.35 ± 1.6
6.05 ± 0.4a 7.40 ± 0.7a 9.0 ± 1.1b 10.55 ± 0.9cb 11.86 ± 1.3c
6.05 ± 0.4a 6.82 ± 0.7a 8.30 ± 0.9ba 9.71 ± 0.7b 10.93 ± 1.4c
6.05 ± 0.4a 6.70 ± 0.5a 7.72 ± 0.6a 9.20 ± 0.5b 10.15 ± 1.2cb
0.32 0.37 0.43 0.78 0.87
± ± ± ± ±
0.02a 0.02a 0.03bc 0.05ed 0.02f
0.32 0.35 0.40 0.74 0.78
± ± ± ± ±
0.02a 0.01a 0.04b 0.03d 0.04ed
0.32 0.34 0.38 0.69 0.73
± ± ± ± ±
0.02a 0.03a 0.03b 0.04d 0.05d
6.05 ± 0.4a 8.85 ± 0.8b 10.55 ± 1.1c 12.91 ± 1.3d 14.85 ± 2.1e
6.05 ± 0.4a 8.25 ± 0.9ba 9.80 ± 0.7b 11.42 ± 1.1c 13.54 ± 1.8ed
6.05 ± 0.4a 7.73 ± 0.6a 8.42 ± 0.8b 10.28 ± 0.9c 12.33 ± 1.6d
6.05 ± 0.4a 7.01 ± 0.4a 8.02 ± 0.5ba 10.11 ± 0.7cb 11.52 ± 1.3c
* European Union Standards (EU Regulation 1989/2003European Communities, 2003EU Regulation 1989/2003) for EVOO. Different letters in same column indicate statistically significant differences (p < 0.05).
for different EVOO samples stored in glass packages (without controlling the headspace) significantly decreased from 519 to 194, 549 to 217, and 433 to 165 (ppm gallic acid) after 3 months storage. Table 3 shows a significant change (p < 0.05) in chlorophylls for EVOO samples in both package types, at both storage temperatures, at different headspace O2 concentrations and storage times. Results show there were no significant differences (p > 0.05) in chlorophyll compounds up to 9 months for the EVOO samples stored with 2% O2 concentration in dark packages at 10 °C. While, 21 and 10% O2 concentration kept the chlorophylls with no significant change (p > 0.05) up to 6 months for EVOO samples stored at 10 °C in dark packages. Moreover, the data for 10, 5, and 2% O2 concentrations in the headspace shows no significant change (p > 0.05) in chlorophylls up to 6 months for EVOO samples stored at room temperature (25–28 °C) in dark packages, while EVOO samples stored at 21% O2 concentration were kept chlorophylls level only up to 3 months. Moreover, results (Table 3) showed that the clear package did not keep the chlorophylls compounds more than 3 months for all headspace O2 concentrations. These results suggest that reducing or controlling oxygen concentration in dark packages during the storage time has a positive effect on chlorophylls compared to the clear package type. In general, EVOO with lower headspace O2 concentrations might be enhancing the concentration of minor compounds during storage and increasing the shelflife of EVOO as well.
1989/2003) up to 9 months for EVOO samples stored with 21% O2 concentration in dark packages and up to 6 months in clear packages. The K232 and K270 values that were obtained in this study were lower than the values reported in several studies for the same package type and storage time (Méndez & Falqué, 2007; Pristouri et al., 2010).
4.3. Headspace O2 concentration on minor compounds Fig. 4 shows a significant change (p < 0.05) in total polyphenols for EVOO samples in both package types, at both storage temperatures, for headspace O2 concentrations and storage time. Results show there were no significant differences (p > 0.05) in total polyphenol levels up to 6 months for EVOO samples stored with 2% O2 concentration in dark packages at 10 °C. While, 5 and 10% O2 concentrations kept the total polyphenol levels up to 3 months (Fig. 4A). In addition, results show there were no significant differences (p > 0.05) in total polyphenol levels up to 3 months for EVOO samples stored with 2 and 5% O2 concentration in clear packages at 10 °C (Fig. 4B). Moreover, the data shows 2% headspace O2 concentrations kept the level of total polyphenols up to 3 months for EVOO samples stored at room temperature (25–28 °C) in dark packages (Fig. 4C), while the EVOO samples stored in clear packages did not keep the level of total polyphenols for more than 3 months (Fig. 4D). These results suggest that reducing or controlling oxygen concentration in the headspace during storage has a positive outcome on total polyphenol compared to previous studies. Méndez and Falqué (2007) who reported that total polyphenol content
Table 2a Changes in absorption coefficients (K232 and K270) of EVOO packaged in dark and clear glass bottles at room temperature (25–28 °C) as a function of headspace O2 concentration and storage time. Values are mean ± SD of 3 replicates and 3 analyses each, n = 9. K232 (≤ 2.5)* Month
10% O2
21% O2
Dark Glass Bottles 0 1.40 ± 3 1.65 ± 6 1.84 ± 9 2.04 ± 12 2.28 ± Clear Glass Bottles 0 1.40 ± 3 1.72 ± 6 1.98 ± 9 2.23 ± 12 2.52 ±
K270 (≤ 0.22)* 5% O2
2% O2
21% O2
10% O2
5% O2
2% O2
0.01a 0.03b 0.03bc 0.05dc 0.05e
1.40 1.58 1.76 1.93 2.09
± ± ± ± ±
0.01a 0.04a 0.05b 0.03c 0.04e
1.40 1.50 1.63 1.75 1.86
± ± ± ± ±
0.01a 0.02a 0.04b 0.05b 0.03bc
1.40 1.45 1.54 1.66 1.75
± ± ± ± ±
0.01a 0.02a 0.03ab 0.02b 0.04b
0.12 0.18 0.22 0.26 0.28
± ± ± ± ±
0.02a 0.03b 0.04c 0.03dc 0.04d
0.12 0.16 0.19 0.22 0.25
± ± ± ± ±
0.02a 0.02b 0.04b 0.05c 0.04c
0.12 0.14 0.16 0.19 0.21
± ± ± ± ±
0.02a 0.03a 0.02b 0.03b 0.02c
0.12 0.14 0.15 0.17 0.19
± ± ± ± ±
0.02a 0.01a 0.03a 0.02b 0.01b
0.01a 0.04b 0.05c 0.03d 0.05d
1.40 1.66 1.89 2.14 2.34
± ± ± ± ±
0.01a 0.05a 0.03b 0.05c 0.06d
1.40 1.57 1.78 1.99 2.16
± ± ± ± ±
0.01a 0.03a 0.05b 0.03c 0.05c
1.40 1.51 1.69 1.86 2.03
± ± ± ± ±
0.01a 0.04a 0.04ba 0.05b 0.03c
0.12 0.21 0.25 0.29 0.32
± ± ± ± ±
0.02a 0.04b 0.03c 0.04d 0.05d
0.12 0.18 0.22 0.24 0.27
± ± ± ± ±
0.02a 0.04b 0.02cb 0.05c 0.05c
0.12 0.15 0.19 0.20 0.22
± ± ± ± ±
0.02a 0.03a 0.03b 0.04b 0.03cb
0.12 0.15 0.18 0.18 0.20
± ± ± ± ±
0.02a 0.04a 0.02b 0.03b 0.02b
* European Union Standards (EU Regulation 1989/2003European Communities, 2003EU Regulation 1989/2003) for EVOO. Different letters in same column indicate statistically significant differences (p < 0.05). 5
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Table 2b Change in absorption coefficients (K232 and K270) of EVOO packaged in dark and clear glass bottles at 10 °C as a function of headspace O2 concentration and storage time. Values are mean ± SD of 3 replicates and 3 analyses each, n = 9. K232 (≤ 2.5)* Month
10% O2
21% O2
Dark Glass Bottles 0 1.40 ± 3 1.60 ± 6 1.78 ± 9 1.95 ± 12 2.19 ± Clear Glass Bottles 0 1.40 ± 3 1.67 ± 6 1.89 ± 9 2.08 ± 12 2.31 ±
K270 (≤ 0.22)* 5% O2
2% O2
± ± ± ± ±
21% O2
10% O2
5% O2
2% O2
0.01a 0.03b 0.04cb 0.02c 0.03d
1.40 1.55 1.73 1.81 2.02
± ± ± ± ±
0.01a 0.02a 0.04b 0.05c 0.04d
1.40 1.46 1.62 1.73 1.86
± ± ± ± ±
0.01a 0.02a 0.03b 0.04b 0.05c
1.40 1.42 1.51 1.64 1.74
0.01a 0.01a 0.02a 0.03b 0.02b
0.12 0.15 0.18 0.21 0.24
± ± ± ± ±
0.02a 0.04b 0.02c 0.03d 0.04d
0.12 0.13 0.15 0.17 0.20
± ± ± ± ±
0.02a 0.01a 0.02b 0.03b 0.02c
0.12 0.12 0.13 0.15 0.18
± ± ± ± ±
0.02a 0.01a 0.03a 0.02b 0.03c
0.12 ± 0.02a 0.12 ± 0.03a 0.13 ± 0.01a 0.15. ± 0.03b 0.16 ± 0.02b
0.01a 0.02b 0.05c 0.03d 0.05f
1.40 1.62 1.82 1.95 2.11
± ± ± ± ±
0.01a 0.04b 0.03c 0.04c 0.04d
1.40 1.57 1.70 1.84 1.95
± ± ± ± ±
0.01a 0.02a 0.04b 0.05c 0.03c
1.40 ± 0.01a 150 ± 0.03a 1.58 ± 0.05a 1.66 ± 0.04b 1.83 ± 0.05c
0.12 0.17 0.21 0.24 0.25
± ± ± ± ±
0.02a 0.03b 0.01c 0.02d 0.03d
0.12 0.15 0.19 0.20 0.22
± ± ± ± ±
0.02a 0.03ba 0.02b 0.03c 0.04c
0.12 0.13 0.15 0.16 0.20
± ± ± ± ±
0.02a 0.02a 0.03ba 0.02b 0.03c
0.12 0.13 0.14 0.15 0.17
± ± ± ± ±
0.02a 0.01a 0.02a 0.01ba 0.02b
* European Union Standards (EU Regulation 1989/2003European Communities, 2003EU Regulation 1989/2003) for EVOO. Different letters in same column indicate statistically significant differences (p < 0.05).
for EVOO samples stored at room temperature (25–28 °C) in both (dark and clear) packages (Fig. 5C) and (Fig. 5D). Because olive oil stability is mainly due to the level of unsaturated fatty acids and antioxidant compounds especially polyphenol compound that has a positive correlation with oxidative stability in virgin olive oil (Baldioli, Servili, Perretti, & Montedoro, 1996: Iqdiam et al., 2019).
4.4. Headspace O2 concentration on oxidative stability index (OSI) Fig. 5 shows a significant change (p < 0.05) in OSI values for EVOO samples packaged in both container types, at both temperatures, as a function of headspace O2 concentrations, and storage time. Results show there were no significant differences (p > 0.05) in OSI values up to 6 months for EVOO samples stored at 2 and 5% O2 concentrations in dark packages at 10 °C storage temperatures. While, 10 and 21% O2 concentrations did not keep the level of OSI for more than 3 months (Fig. 5A). In addition, results show 2 and 5% O2 concentrations kept the OSI constant up to 3 months only for EVOO samples stored at 10 °C in clear package, while the EVOO samples stored with 10 and 21% O2 concentrations did not keep the level of OSI for more than 3 months (Fig. 5B). Low O2 MAP technology did not significantly improve the OSI
4.5. Headspace O2 concentration on EVOO color Tables 4a and 4b shows a significant change (p < 0.05) in EVOO color in both package types, at both storage temperatures, as a function of headspace O2 concentration, and storage time. Table 4a shows there were no significant differences (p > 0.05) in oil color parameters up to 9 months for the EVOO samples stored at 2 and 5% O2 concentrations in
Fig. 4. Changes in total polyphenols (mg/kg) of EVOO samples as a function of headspace O2 concentration and storage time. A) Dark container at 10 °C, B) Clear container at 10 °C, C) Dark container at (25–28 °C), and D) Clear container at (25–28 °C). Error bars represent mean ± SD of 3 experiments and 3 readings at each time, n = 9. Different letters indicate statistically significant differences at (p < 0.05). 6
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Table 3 Changes in Chlorophylls (mg/kg) of EVOO packaged in dark and clear glass bottles at room temperature (25–28 °C) and 10 °C as a function of headspace oxygen concentration and storage time. Values are mean ± SD of 3 replicates and 3 analyses each, n = 9. Room temperature (25 – 28 °C) Month
10% O2
21% O2
Dark Glass Bottles 0 7.10 ± 3 6.72 ± 6 6.31 ± 9 6.03 ± 12 5.81 ± Clear Glass Bottles 0 7.10 ± 3 6.31 ± 6 5.82 ± 9 5.33 ± 12 4.84 ±
Temperature 10 °C 5% O2
2% O2
21% O2
10% O2
5% O2
2% O2
0.45a 0.51b 0.70c 0.41d 0.36d
7.10 6.77 6.42 6.14 5.94
± ± ± ± ±
0.45a 0.35ba 0.48c 0.29c 0.55d
7.10 6.85 6.53 6.26 6.15
± ± ± ± ±
0.45a 0.48a 0.63b 0.44c 0.57c
7.10 6.90 6.58 6.35 6.23
± ± ± ± ±
0.45a 0.55a 0.65b 0.54c 0.71c
7.10 6.83 6.56 6.30 6.07
± ± ± ± ±
0.45a 0.38a 0.47b 0.52cb 0.45b
7.10 6.87 6.64 6.39 6.18
± ± ± ± ±
0.45a 0.62a 0.35b 0.56b 0.43b
7.10 6.98 6.73 6.48 6.29
± ± ± ± ±
0.45a 0.49a 0.52a 0.61b 0.54cb
7.10 7.04 6.82 6.54 6.37
± ± ± ± ±
0.45a 0.5 8a 0.29a 0.53b 0.46b
0.45a 0.72b 0.57c 0.48d 0.73e
7.10 6.35 6.02 5.39 4.95
± ± ± ± ±
0.45a 0.66b 0.44c 0.64d 0.58e
7.10 6.48 6.14 5.47 5.14
± ± ± ± ±
0.45a 0.55b 0.71b 0.62d 0.49ed
7.10 6.52 6.21 5.58 5.27
± ± ± ± ±
0.45a 0.47b 0.65b 0.54c 0.61d
7.10 6.43 6.02 5.73 5.19
± ± ± ± ±
0.45a 0.56b 0.44c 0.53c 062d
7.10 6.54 6.08 5.78 5.26
± ± ± ± ±
0.45a 0.39b 0.55c 0.48c 0.36d
7.10 6.62 6.17 5.85 5.34
± ± ± ± ±
0.45a 0.51b 0.37c 0.55c 0.43d
7.10 6.68 6.25 5.91 5.42
± ± ± ± ±
0.45a 0.72b 0.51b 0.58c 0.49d
Different letters indicate statistically significant differences (p < 0.05).
room temperature (25–28 °C). These results suggest that lower O2 concentration in the headspace during storage has a positive influence on EVOO color compared to previous studies regarding EVOO storage time (Méndez & Falqué, 2007; Pristouri et al., 2010). Generally, packaging EVOO with lower headspace O2 concentrations might help to maintain EVOO color during storage.
dark packages for both storage temperatures. Data shows no significant differences (p > 0.05) in oil color parameters up to 6 months for EVOO samples stored at 10% O2 concentrations in dark packages at 10 °C, while no significant differences (p > 0.05) in oil color parameters up to 3 months occurred for EVOO samples stored at 10% O2 concentrations in dark packages at room temperature (25–28 °C). Additionally, Table 4b shows there were no significant differences (p > 0.05) in oil color parameters up to 6 months for EVOO samples stored at 2 and 5% O2 concentrations in clear packages for both storage temperatures. Data shows no significant differences (p > 0.05) in oil color parameters up to 3 months for EVOO samples stored with 10% O2 concentrations in clear packages at both storage temperatures while no significant differences (p > 0.05) in oil color parameters resulted up to 3 months for EVOO samples stored at 10% O2 concentrations in dark packages at
5. Conclusion Low headspace oxygen concentration is important for maintaining quality and shelf-life of EVOO. Based upon data presented here, the following conclusions may be drawn: (a) EVOO at 2 and 5% headspace oxygen, in glass containers (clear or dark), at room temperature and 10 °C protects chemical indices of EVOO beyond 12 months; (b) EVOO
Fig. 5. Changes in OSI (induction time h.) of EVOO samples as a function of headspace O2 concentration and storage time. A) Dark container at 10 °C, B) Clear container at 10 °C, C) Dark container at (25–28 °C), and D) Clear container at (25–28 °C). Error bars represent mean ± SD of 3 experiments and 3 readings at each time, n = 9. Different letters indicate statistically significant differences at (p < 0.05). 7
21% O2
± ± ± ± ± ± ± ± ± ± ± ± ± ± ±
0.30a 0.05a 0.15a 0.62a 0.03b 0.24b 0.30b 0.02c 0.32cb 0.62c 0.05c 0.38c 0.37c 0.02d 0.40d
L = 80.25 a = -0.38 b = 78.62 L = 79.16 a = -0.40 b = 77.42 L = 77.96 a = -0.44 b = 76.25 L = 75.39 a = -0.45 b = 74.15 L = 74.75 a = -0.47 b = 72.83
10% O2
± ± ± ± ± ± ± ± ± ± ± ± ± ± ±
0.30a 0.05a 0.15a 0.27a 0.02a 0.55a 0.55b 0.05b 0.60b 0.30cb 0.04c 0.62c 0.68c 0.03c 0.32c
L = 80.25 a = -0.38 b = 78.62 L = 80.08 a = -0.39 b = 78.44 L = 78.73 a = -0.41 b = 77.45 L = 76.81 a = -0.43 b = 76.18 L = 75.37 a = -0.45 b = 74.35
5% O2
± ± ± ± ± ± ± ± ± ± ± ± ± ± ±
0.30a 0.05a 0.15a 0.18a 0.01a 0.26a 0.59a 0.03ba 0.35a 0.62b 0.03b 0.45b 0.40cb 0.05c 0.28c
L = 80.25 a = -0.38 b = 78.62 L = 80.14 a = -0.38 b = 78.54 L = 79.24 a = -0.40 b = 77.85 L = 77.60 a = -0.42 b = 76.88 L = 76.81 a = -0.44 b = 75.65
2% O2
± ± ± ± ± ± ± ± ± ± ± ± ± ± ±
0.30a 0.05a 0.15a 0.27a 0.02a 0.64a 0.25a 0.02a 0.66a 0.38b 0.02ba 0.25b 0.60b 0.04cb 0.32cb
L = 80.25 a = -0.38 b = 78.62 L = 79.69 a = -0.40 b = 77.45 L = 77.24 a = -0.42 b = 76.15 L = 75.83 a = -0.45 b = 74.58 L = 74.22 a = -0.46 b = 72.19
21% O2
± ± ± ± ± ± ± ± ± ± ± ± ± ± ±
0.30a 0.05a 0.15a 0.51a 0.02a 0.38a 0.36b 0.04b 0.75b 0.27c 0.03c 0.42c 0.55c 0.03c 0.30d
Temperature 10 °C
L = 80.25 a = -0.38 b = 78.62 L = 80.01 a = -0.39 b = 77.93 L = 77.92 a = -0.40 b = 76.85 L = 76.48 a = -0.44 b = 75.28 L = 75.65 a = -0.45 b = 74.50
10% O2
± ± ± ± ± ± ± ± ± ± ± ± ± ± ±
0.30a 0.05a 0.15a 0.72a 0.04a 0.52a 0.52b 0.03a 0.48ba 0.36cb 0.04c 0.61cb 0.28c 0.02c 0.62c
L = 80.25 a = -0.38 b = 78.62 L = 80.12 a = -0.38 b = 78.27 L = 78.81 a = -0.39 b = 77.55 L = 78.08 a = -0.41 b = 76.55 L = 76.22 a = -0.43 b = 75.34
5% O2
± ± ± ± ± ± ± ± ± ± ± ± ± ± ±
0.30a 0.05a 0.15a 0.19a 0.03a 0.58a 0.27ba 0.04a 0.40a 0.25b 0.03ba 0.42b 0.37cb 0.05b 0.28c
L = 80.25 a = -0.38 b = 78.62 L = 80.18 a = -0.38 b = 78.48 L = 79.25 a = -0.39 b = 77.81 L = 78.92 a = -0.40 b = 76.96 L = 77.45 a = -0.41 b = 75.94
2% O2
± ± ± ± ± ± ± ± ± ± ± ± ± ± ±
0.30a 0.05a 0.15a 0.22a 0.05a 0.11a 0.62a 0.03a 0.50a 0.45ba 0.05a 0.40b 0.42b 0.02ba 0.50c
8
21% O2
± ± ± ± ± ± ± ± ± ± ± ± ± ± ±
0.30a 0.05a 0.15a 0.62ba 0.02b 0.33b 0.35cb 0.05b 0.58c 0.25c 0.03c 0.41c 0.32d 0.02d 0.54c
L = 80.25 a = -0.38 b = 78.62 L = 78.02 a = -0.42 b = 76.11 L = 75.82 a = -0.45 b = 74.19 L = 73.58 a = -0.47 b = 72.15 L = 70.40 a = -0.48 b = 71.31
10% O2
± ± ± ± ± ± ± ± ± ± ± ± ± ± ±
0.30a 0.05a 0.15a 0.45a 0.03a 0.20a 0.42b 0.02b 0.27b 0.35c 0.05b 0.30c 0.59dc 0.04c 0.27c
L = 80.25 a = -0.38 b = 78.62 L = 79.64 a = -0.41 b = 77.25 L = 77.18 a = -0.42 b = 76.73 L = 75.26 a = -0.44 b = 74.11 L = 73.48 a = -0.45 b = 73.38
5% O2
Different letters indicate statistically significant differences (p < 0.05).
Clear Glass Bottles 0 L = 80.25 a = -0.38 b = 78.62 3 L = 77.08 a = -0.44 b = 74.11 6 L = 74.22 a = -0.47 b = 72.44 9 L = 71.18 a = -0.49 b = 70.44 12 L = 68.20 a = -0.51 b = 69.34
Month
Room temperature (25 – 28 °C)
± ± ± ± ± ± ± ± ± ± ± ± ± ± ±
0.30a 0.05a 0.15a 0.48a 0.04a 0.35a 0.27ba 0.04a 0.38a 0.64b 0.02b 0.33b 0.36c 0.03b 0.46b
L = 80.25 a = -0.38 b = 78.62 L = 79.70 a = -0.40 b = 77.61 L = 78.31 a = -0.42 b = 76.91 L = 76.18 a = -0.43 b = 75.71 L = 75.25 a = -0.44 b = 74.42
2% O2
± ± ± ± ± ± ± ± ± ± ± ± ± ± ±
0.30a 0.05a 0.15a 0.36a 0.03a 0.60a 0.55a 0.02a 0.63a 0.44b 0.03a 0.55b 0.35b 0.02b 0.55b
L = 80.25 ± 0.30a a = -0.38 ± 0.05a b = 78.62 ± 0.15a L = 78.20 ± 0.52a a = -0.43 ± 0.02b b = 76.3 ± 0.47a L = 75.88 ± 0.70b a = -0.45 ± 0.03b b = 74.38 ± 0.25b L = 73.10 ± 0.22c a = -0.47 ± 0.04c b = 72.68 ± 0.20c L = 71.55 ± 0.42d a = -0.49 ± 0.03d b = 70.65 ± 0.47d
21% O2
Temperature 10 °C
L = 80.25 a = -0.38 b = 78.62 L = 79.50 a = -0.41 b = 77.27 L = 76.44 a = -0.43 b = 75.58 L = 74.45 a = -0.45 b = 74.35 L = 73.25 a = -0.47 b = 72.33
10% O2
± ± ± ± ± ± ± ± ± ± ± ± ± ± ±
0.30a 0.05a 0.15a 0.39a 0.04a 0.28a 0.50b 0.04b 0.25b 0.31c 0.03b 0.20b 0.55c 0.04c 0.28c
L = 80.25 a = -0.38 b = 78.62 L = 79.05 a = -0.40 b = 78.12 L = 77.25 a = -0.42 b = 76.48 L = 75.82 a = -0.43 b = 75.35 L = 74.48 a = -0.45 b = 73.85
5% O2
± ± ± ± ± ± ± ± ± ± ± ± ± ± ±
0.30a 0.05a 0.15a 0.20a 0.03a 0.24a 0.50ba 0.03ba 0.25a 0.50cb 0.04b 0.45b 0.29c 0.01b 0.52cb
L = 80.25 a = -0.38 b = 78.62 L = 79.63 a = -0.40 b = 78.36 L = 77.45 a = -0.42 b = 77.19 L = 76.55 a = -0.43 b = 76.61 L = 75.80 a = -0.44 b = 75.20
2% O2
± ± ± ± ± ± ± ± ± ± ± ± ± ± ±
0.30a 0.05a 0.15a 0.32a 0.02a 0.17a 0.30ba 0.01ba 0.24a 0.28b 0.02b 0.25a 0.36b 0.04b 0.18b
Table 4b Changes in color of EVOO packaged in clear glass bottles at room temperature (25–28 °C) and 10 °C as a function of headspace oxygen concentration and storage time. Values are mean ± SD of 3 replicates and 3 analyses each, n = 9.
Different letters indicate statistically significant differences (p < 0.05).
Dark Glass Bottles 0 L = 80.25 a = -0.38 b = 78.62 3 L = 78.31 a = -0.42 b = 76.11 6 L = 76.75 a = -0.46 b = 74.41 9 L = 74.20 a = -0.47 b = 72.17 12 L = 73.28 a = -0.49 b = 70.25
Month
Room temperature (25 – 28 °C)
Table 4a Changes in color of EVOO packaged in dark glass bottles at room temperature (25–28 °C) and 10 °C as a function of headspace oxygen concentration and storage time. Values are mean ± SD of 3 replicates and 3 analyses each, n = 9.
B.M. Iqdiam, et al.
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with 2% headspace oxygen in dark bottles at 10 °C protects total polyphenols of EVOO beyond 6 months; (c) EVOO with 2 and 5% headspace oxygen in dark bottles at 10 °C protects chlorophylls of EVOO beyond 6 months; (d) EVOO with 2% oxygen headspace, in dark glass containers at 10 °C protects the OSI of EVOO beyond 6 months; and (e) EVOO with 2 and 5% headspace oxygen in dark bottles at 10 °C protects color parameters of EVOO beyond 9 months. Overall, low oxygen MAP technology appears viable for enhancing the shelf-life of EVOO during storage. Understanding how MAP technology influences EVOO quality and shelf-life will ultimately assist processors in improving the storage conditions for EVOO. Combining MAP technology and other factors such as packaging type, package headspace volume, and storage temperature are likely to present potential advantages for EVOO storage.
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