Plasticizer types and coating methods affect quality and shelf life of eggs coated with chitosan

ABSTRACT:  Effects of different plasticizer types (glycerol, propylene glycol, and sorbitol) and coating methods (brushing, dipping, and spraying) on the internal quality and shelf life of chitosan-coated eggs were evaluated during 5 wk of storage at 25 °C. The Haugh unit and yolk index values suggested that chitosan coating, irrespective of the plasticizer types, extended the shelf life of eggs by almost 3 wk at 25 °C compared with noncoated eggs. After 5 wk of storage, plasticizer types did not significantly affect the quality (weight loss, Haugh unit, and yolk index) of chitosan-coated eggs. However, there was an observable trend indicating that use of sorbitol rather than propylene glycol and glycerol as a plasticizer was better in reducing weight loss (whole egg) of chitosan-coated eggs during a 5-wk storage. After a 5-wk storage, there were no significant differences in weight loss and weight of albumen and yolk among chitosan-coated eggs, regardless of the coating methods. However, both brushing and dipping methods yielded chitosan-coated eggs with better yolk (higher yolk index values) and albumen (lower pH) qualities than did the spraying method. During 3 to 5 wk of storage, the Haugh unit values of chitosan-coated eggs by the brushing method were higher than or comparable to those by dipping or spraying. Therefore, coating of eggs with chitosan using sorbitol as a plasticizer and by the brushing method may offer a protective barrier in preserving the internal quality and thus extending shelf life of eggs.     

Selected Quality and Shelf Life of Eggs Coated with Mineral Oil with Different Viscosities

ABSTRACT:  Selected quality and shelf life of eggs coated with mineral oil having 6 different viscosities (7, 11, 14, 18, 22, and 26 cP) were evaluated during 5 wk of storage at 25 °C. As the storage time increased, weight loss and albumen pH increased whereas Haugh unit and yolk index values decreased. After 5 wk of storage, eggs coated with 11, 14, 18, 22, or 26 cP oil possessed better quality than the control noncoated eggs and eggs coated with 7 cP oil. Oil coating, irrespective of viscosities, did not improve the emulsion capacity. There was an observable trend that coating with 26 cP oil was more effective in preventing weight loss and in maintaining the Haugh unit of eggs compared with coating with other viscosities of mineral oil. Based on the Haugh unit, the grade of noncoated eggs changed from "AA" at 0 wk to "C" after 3 wk whereas that of 26 cP oil-coated eggs from "AA" at 0 wk to "A" at 3 wk and "B" at 5 wk of storage. Coating with 26 cP oil reduced the weight loss of eggs by more than 10 times (0.85% compared with 8.78%) and extended the shelf life of eggs by at least 3 more weeks compared with the noncoated eggs.     

Effect of Plasticizer Concentration and Solvent Types on Shelf-life of Eggs Coated with Chitosan

ABSTRACT:  Effects of plasticizer concentrations (0, 0.5, 1.0, 1.5, and 2.0% glycerol) and solvent types (1% acetic and 1% lactic acid) on internal quality of eggs coated with 2% chitosan solution were evaluated during 5 wk of storage at 25 °C. In comparison of plasticizer concentrations, eggs coated with chitosan dissolved in acetic acid containing 2% glycerol showed significant reduction in weight loss compared with the noncoated eggs during 5 wk of storage. At 2% glycerol, the Haugh unit and yolk index values suggested that chitosan-coated eggs can be preserved for at least 3 wk longer than the control noncoated eggs during 5 wk of storage at 25 °C. Use of acetic acid rather than lactic acid as a chitosan solvent was more advantageous in view of shelf-life extension of eggs.     

Effect of molecular weight, type of chitosan, and chitosan solution pH on the shelf-life and quality of coated eggs

ABSTRACT:  Effects of the molecular weight and type of chitosans and pH of chitosan solution on antibacterial activity against Salmonella enterica Enteritidis and on internal quality of chitosan-coated eggs were evaluated during 4 wk of storage at 25 °C. Two types of chitosans were studied: α-chitosans with 4 different molecular weights (Mw = 282, 440, 746, and 1110 kDa) and β-chitosan (Mw = 577 kDa). The α-chitosan with 282 kDa exhibited stronger bactericidal effects than did other α- and β-chitosans. The weight loss, Haugh unit, and yolk index values suggested that coating of eggs with α-chitosan with 282 kDa increased the shelf-life of eggs by almost 3 wk at 25 °C compared with noncoated eggs. The pH (4.5, 5.0, and 5.5) of the α-chitosan (282 kDa) solution did not affect the internal quality of chitosan-coated eggs. Therefore, coating of eggs with 282 kDa α-chitosan without pH adjustment (initial pH of 4.5) may offer a protective barrier against contamination of S. Enteritidis while simultaneously preserving the internal quality of eggs.     

Internal quality and shelf life of eggs coated with oils from different sources

Selected internal quality and shelf life of eggs coated with oils from differences sources (mineral oil, canola oil, corn oil, grape seed oil, olive oil, soybean oil, and sunflower oil) were evaluated during 5 wk of storage at 25 °C. As the storage time increased, weight loss increased whereas Haugh unit and yolk index values decreased. Throughout the 5 wk of storage, eggs coated with oils, regardless of oil sources, possessed better albumen and yolk quality than the control noncoated eggs. Oil coating minimized weight loss of eggs (<0.8%) compared with that (7.26%) of the noncoated eggs after 5 wk of storage at 25 °C. No significant differences in internal quality (weight loss, Haugh unit, yolk index, and albumen pH) were generally observed among oil-coated eggs during 5 wk of storage. Based on the Haugh unit, the grade of noncoated eggs changed from AA at 0 wk to A at 1 wk and to B after 3 wk whereas that of oil-coated eggs from AA at 0 wk to A at 4 wk and maintained A grade until 5 wk. This study demonstrated that oil coating, irrespective of oil sources, preserved the internal quality, minimized weight loss (<0.8%), and extended the shelf life of eggs by at least 3 wk longer than observed for the noncoated eggs at 25 °C storage. Soybean oil was a more practical option as a coating material for eggs due to its low cost. PRACTICAL APPLICATION: Eggs are highly perishable and susceptible to internal quality deterioration when stored above 7 °C. Refrigeration of eggs may be seldom practiced in some developing regions of the world. Therefore, an alternative method, that is inexpensive yet effective, to preserve the internal quality of eggs and to prevent microbial contamination is needed. Oil coating has been proven to preserve the internal quality, prolong shelf life, and minimize weight loss of eggs. This study demonstrated that, compared with other vegetable oils, soybean oil was a more practical option as a coating material for eggs during 5 wk of storage at 25 °C due to its low cost.     

A novel emulsion coating and its effects on internal quality and shelf life of eggs during room temperature storage

Effects of mineral oil (MO), chitosan solution (CH) and their emulsions (MO:CH = 75:25, 50:50, and 25:75 ratios) as coating materials in preserving internal quality of eggs were evaluated during a 5‐weeks storage at 25 °C. Consumers (n = 109) evaluated surface properties and purchase intent of freshly coated eggs. As storage time increased, Haugh unit and yolk index values decreased whereas weight loss increased. Noncoated eggs rapidly changed from AA to B and C grades after 1 and 3 weeks, respectively. However, all emulsion‐coated eggs maintained their A‐grade quality for 4 weeks. Compared with noncoated eggs, all emulsion coatings reduced weight loss of eggs by at least seven times (0.88–1.03% vs. 7.14%). Only MO:CH = 25:75 emulsion‐coated eggs were not sensorially glossier than noncoated eggs. All emulsion‐coated eggs had >80% positive purchase intent and were negative for Salmonella. This study demonstrated that MO:CH emulsion coatings preserved internal quality and prolonged shelf life of eggs.     

Edible coating affects physico‐functional properties and shelf life of chicken eggs during refrigerated and room temperature storage

Effects of chitosan, whey protein concentrate (WPC), mineral oil (MO) and/or soybean oil (SO) coating on egg quality were compared at 25 and 4 °C, respectively, during 5 and 20 weeks of storage. Storage time and temperature, and type of coating significantly affected Haugh unit, yolk index, weight loss, albumen pH and emulsifying capacity. Shelf life was extended 4 weeks by MO and SO and 2 weeks by chitosan and WPC longer than that observed for noncoated eggs at 25 °C. MO‐ and SO‐coated eggs maintained AA grade for 20 weeks at 4 °C. Weight loss of SO‐coated eggs was <1% after 5 weeks at 25 °C and after 20 weeks at 4 °C. Yolk index and emulsifying capacity were more correlated at 25 °C than at 4 °C. MO and SO were more effective coating materials, with SO providing a more cost‐effective coating for extending egg shelf life.     

Chitosan Coating Improves Shelf Life of Eggs

ABSTRACT: Internal and sensory quality of eggs coated with chitosan was evaluated during a 5-wk storage at 25 °C. Three chitosans with high (HMw, 1100 KDa), medium (MMw, 746 KDa), and low (LMw, 470 KDa) molecular weight were used to prepare coating solutions. Coating with LMw chitosan was more effective in preventing weight loss than with MMw and HMw chitosans. The Haugh unit and yolk index values indicated that the albumen and yolk quality of coated eggs can be preserved up to 5 wk at 25 °C, which is at least 3 wk longer than observed for the control noncoated eggs. Based on external quality, consumers could not differentiate the coated eggs from the control noncoated eggs. Overall acceptability of all coated eggs was not different from the control and commercial eggs.     

Effects of initial albumen quality and mineral oil–chitosan emulsion coating on internal quality and shelf‐life of eggs during room temperature storage

Effects of mineral oil (MO) and mineral oil–chitosan emulsion (MO:CH = 25:75) as coatings on internal quality and shelf‐life of eggs were evaluated during 5‐week storage at 25 °C. Eggs with three different initial albumen qualities [Haugh unit (HU): H = 87.8, M = 75.6 and L = 70.9] were evaluated. As storage time increased, HU and yolk index values decreased whereas weight loss increased. Coating with MO and/or 25:75 MO:CH emulsion could preserve the internal quality for at least 4 more weeks for H‐eggs and at least 3 more weeks for M and/or L‐eggs, all with weight losses <0.92%. All coated eggs had >70% positive purchase intent, and their colour differences at week 0 could not be detected by naked human eye (ΔE^* < 3.0, noncoated eggs as reference). Consumers significantly differentiated freshly MO‐coated from noncoated eggs on overall surface appearance. This study demonstrated that MO and 25:75 MO:CH emulsion coatings could preserve internal quality and prolong shelf‐life of eggs.     

Effects of mineral oil coating on internal quality of chicken eggs under refrigerated storage

The selected internal qualities (weight loss, Haugh unit, yolk index, and albumen pH) of noncoated and mineral oil‐coated chicken eggs during 15 weeks of storage at 4 °C and/or during 5 weeks of storage at 25 °C were evaluated. Results indicated that, without refrigeration, the noncoated and mineral oil‐coated eggs rapidly changed from AA to C and B grades as measured by Haugh unit, respectively, after 5 weeks of storage. However, the AA quality of the noncoated eggs could be maintained under refrigerated storage (4 °C) for at least 5 weeks. The mineral oil coating and refrigerated storage (4 °C) synergistically minimised weight loss and preserved the albumen and yolk qualities of chicken eggs during a long‐term storage. At 4 °C, the mineral oil‐coated eggs preserved the initial AA grade for at least 15 weeks with l.19% weight loss.     

Comparing effects of α‐ vs. β‐chitosan coating and emulsion coatings on egg quality during room temperature storage

Effects of α‐ and β‐chitosan (CH), soybean oil (SO) and their emulsions (CH:SO = 2:3) as coating materials on selected internal quality and sensory properties of eggs were evaluated during 5 weeks storage at 25 °C. After 3 weeks of storage, α‐ and β‐CH‐coated eggs changed to B grade, while SO‐ and emulsion‐coated eggs preserved grade A quality. Weight loss of eggs coated with SO and CH:SO emulsions was <2.0% vs. 5.3–5.8% for noncoated and CH‐coated eggs after 5 weeks of storage. β‐CH (0.9%) maintained lower weight loss of eggs than α‐CH (1.2%) only at 1‐week storage. Albumen pH of eggs coated with SO and CH:SO emulsions decreased progressively throughout storage. Eggs coated with β‐CH:SO emulsion and SO were significantly glossier than noncoated eggs. Consumers indicated positive purchase intent (69.17–76.67%) for all coated eggs. Overall, α‐CH:SO and β‐CH:SO emulsions extended egg shelf life by at least 3 weeks during room temperature storage.     

Mineral oil-chitosan emulsion coatings affect quality and shelf-life of coated eggs during refrigerated and room temperature storage

Effects of mineral oil (MO) and 4 emulsions (prepared with different emulsifier types) of MO and chitosan solution (CH) at a fixed ratio of MO:CH = 25:75 as coating materials in preserving the internal quality of eggs were evaluated during 5 wk at 25 °C and 20 wk at 4 °C. Generally, as storage time increased, Haugh unit and yolk index values decreased whereas weight loss increased. However, MO and/or 4 emulsion coatings minimized the weight loss (<1.5%) and preserved the albumen and yolk quality of eggs (with the final B grade) for at least 3 wk longer than those observed for noncoated eggs at 25 °C. At 4 °C, all coated eggs changed from AA to A grade after 5 wk and they maintained this grade for 10 wk (5 wk longer than that of noncoated eggs). Although refrigeration (4 °C) alone could maintain the B grade of noncoated eggs for up to 20 wk, coating treatments were necessary to keep the weight loss below 2%. Compared with 4 °C, the increasing weight loss showed stronger negative correlation (P < 0.01) with the decreasing Haugh unit (-0.46 to -0.89) and yolk index (-0.36 to -0.89) at 25 °C. The emulsifier type used in this study generally did not affect the internal quality of eggs. Salmonella spp. detection was negative for all coated and noncoated eggs. This study demonstrated that MO and MO:CH emulsion coatings preserved the internal quality, prolonged the shelf-life, and minimized weight loss (<2%) of eggs.     

Oil Coating Affects Internal Quality and Sensory Acceptance of Selected Attributes of Raw Eggs during Storage

Four (coconut, palm, rice bran, and soybean) edible oils and glycerol were applied on eggshell. All noncoated and coated eggs were stored for 5 wk at 25 ± 2 °C and drawn weekly for quality evaluation. All oil coatings were more effective in preserving internal quality of eggs than was glycerol coating. As storage time increased, the preservative effects of edible oil coating on weight loss, and albumen and yolk quality were significantly noticed. Oil‐coated eggs had significantly lower weight loss (<0.43%) than did noncoated (3.87%) and glycerol‐coated (3.73%) eggs after 5 wk of storage. Based on the Haugh unit, oil‐coated eggs maintained AA grade up to 3 wk. After 5 wk of storage, noncoated, glycerol‐coated, and oil‐coated eggs changed from AA grade to below B, below B and A grade, respectively. The albumen pH of noncoated and glycerol‐coated eggs considerably increased from 8.23 to 9.51 and 9.42, respectively, while those of oil‐coated eggs either maintained or slightly increased to 8.32. The albumen viscosity of all eggs decreased with increased storage time. Consumers (N = 120) could differentiate surface glossiness of oil‐coated eggs from uncoated eggs (R‐index of 81.42% to 86.99%). All oil‐coated eggs were acceptable for surface glossiness (liking scores of 6.22 to 6.77) and surface odor (liking scores of 6.20 to 6.55) with overall liking scores of 6.34 to 7.03. Overall, this study demonstrated that edible oil (coconut, palm, rice bran, and soybean) coating could preserve internal quality of eggs (maintaining grade A) at least 4 wk longer than noncoated eggs. Practical Application: Freshness is a major contribution to the egg quality. The internal quality of eggs begins to deteriorate after they have been laid due to loss of moisture and carbon dioxide via the eggshell pores. Refrigeration is very effective in preserving egg quality. Surface coating is an alternative method to preserve egg quality, although it is much less effective than refrigeration. This study demonstrated that coconut, rice bran, soybean, and palm oils, which are abundant and commonly consumed in many parts of the world, could preserve the internal quality and reduce weight loss of oil‐coated eggs during room temperature storage.     

Soybean oil‐chitosan emulsion affects internal quality and shelf‐life of eggs stored at 25 and 4 °C

Effects of soybean oil (SO), chitosan solution (CH) and their emulsions (SO:CH = 60:40, 50:50 and 40:60 ratios) as coatings on internal quality of eggs stored at 25 and 4 °C, respectively, for 7 and 20 weeks, were evaluated. Eggs coated with SO and SO:CH emulsions maintained grade AA and/or A quality up to 7 weeks at 25 °C and 20 weeks at 4 °C, while noncoated eggs changed from AA to B grade after 2 weeks at 25 °C. Compared with noncoated eggs, shelf‐life of eggs stored at 25 °C was extended for 5 weeks by all SO:CH emulsions. Weight loss of eggs coated with SO:CH emulsions was <3% after 7 weeks at 25 °C and <5% after 20 weeks at 4 °C. SO:CH emulsion is alternatively an effective coating with possible shorter drying times for reducing weight loss and preserving the internal quality of eggs.     

Chitosan-soybean oil emulsion coating affects physico-functional and sensory quality of eggs during storage

Effects of soybean oil (SO) and chitosan-soybean oil (CH:SO = 40:60) emulsion as coating materials for preserving internal quality of eggs were evaluated during 7 and 15 weeks storage at 25 °C and 4 °C, respectively. Consumers (n = 150) assessed surface properties and purchase intent of freshly coated eggs. Noncoated eggs deteriorated from AA to B grade after 1 week while coated eggs retained A grade up to 5 weeks at 25 °C. Amongst coatings, CH:SO emulsion maintained a lower albumen pH while SO was better at reducing weight loss. Effect of refrigeration on albumen pH was minimal. Weight loss of coated eggs was <3% after 7 weeks at 25 °C. Emulsion capacity and emulsion viscosity were minimally affected by coating and refrigeration, and their trends were more correlated to the yolk index at 25 °C than at 4 °C. Only SO-coated eggs were not sensorially smoother than noncoated eggs; however, CH:SO emulsion-coated eggs had the least shell colour changes (ΔE^∗, values at day 0 as a reference) during storage at 25 °C. All coated eggs had 85% positive purchase intent. SO and CH:SO emulsion coatings significantly extended egg shelf-life compared to that of noncoated eggs at room and refrigerated storage.     

Effectiveness of chitosan‐based coating in improving shelf‐life of eggs

Despite eggs having a natural packaging—shell—they are perishable and can lose their quality during storage. Chitosan‐based coatings were applied to shell eggs to examine potential effects on egg quality properties (weight loss, Haugh unit, yolk index) during 4 weeks of storage. Mineral amounts in yolks were also evaluated after 4 weeks of storage. Three chitosan‐based coatings produced with organic acids (acetic‐(C‐AA), lactic‐(C‐LA), and propionic (C‐PA)) were evaluated on shelf‐life enhancements of fresh egg quality. All chitosan‐coated eggs showed greater interior quality than the non‐coated eggs. The coatings significantly maintained weight loss compared to the control specimen (4.96%). Lower weight loss (3.45% for C‐PA, 3.53% for C‐LA) was observed in the coated eggs. Eggshell chitosan coat containing lactic and propionic acids maintained higher Haugh unit and yolk index than eggs coated with acetic acid. Uncoated (UC) eggs changed from grade ‘A’ to ‘B’ after 1 week of storage. Chitosan‐based coating containing lactic and propionic acids maintained eggs in grade ‘A’ for 4 weeks. Haugh unit showed that C‐LA and C‐PA effectively maintained eggs at grade ‘A’ quality for at least 3 weeks more than control and 1 week more than C‐AA. Results also indicated that the chitosan coating maintained mineral amounts at nutritional values (especially calcium, iron and magnesium concentration) in yolks after 4 weeks storage. Copyright © 2006 Society of Chemical Industry     

Comparison of Shelf Life of Eggs Coated with Chitosans Prepared under Various Deproteinization and Demineralization Times

Internal quality of eggs coated with chitosans prepared under various deproteinization (DP at 0, 5, 15 min) and demineralization (DM at 0, 10, 20, 30 min) times was evaluated. Chitosans prepared under DP 0 min/DM 30 min, DP 5 min/DM 30 min, and/or DP 15 min/DM 20 min conditions can be effectively used as an egg‐coating material in preserving the internal quality of eggs compared with chitosan prepared under the DP 15 min/DM 30 min condition. The Haugh unit and yolk index values suggested that the chitosan‐coated eggs can be preserved for at least 2 wk longer than the control noncoated eggs during 5 wk of storage at 25°C.     

Methyl jasmonate coupled with modified atmosphere packaging to extend shelf life of tomato (Lycopersicon esculentum Mill.) during cold storage

The effects of methyl jasmonate coupled with modified atmosphere packaging (MJ+MAP) on the quality and shelf life of mature green tomato ( Lycopersicon esculentum Mill.) were investigated during cold storage at 5 °C. Tomatoes were treated with 10⁻⁴  m MJ and packaged under 5%O₂/5%CO₂/90%N₂ in a plastic bag. The effects of MJ+MAP were compared with control as well as heat treated (HT) samples. Control samples were tomatoes packaged under atmospheric air. HT samples were prepared by dipping tomatoes in hot water at 50 °C for 3 min and packaged under atmospheric air. The results showed that MJ+MAP and HT could delay ethylene production during tomato ripening and consequently slowed down the softening rate. MJ+MAP tomatoes showed better quality and less chilling injury (CI) symptoms than HT and control samples. Based on a nine-point score, shelf life criteria assumed that rejection would occur when the sensory attributes declined below 5. Control and HT overall acceptance scores were shown to fall below 5 scores after 3 and 6 weeks storage, while MJ+MAP had overall acceptance scores above 5 for up to 9 weeks. Control and HT samples could be stored for about 4 and 6 weeks, respectively, while MJ+MAP tomatoes could be stored for up to 9 weeks.     

Effect of whey protein isolate-pullulan edible coatings on the quality and shelf life of freshly roasted and freeze-dried Chinese chestnut

ABSTRACT:  Harvested chestnut is characterized by a short shelf life, exposing many Chinese producers to a storage problem as product losses are very high. The objective of this study was to develop a suitable technology to extend the shelf life of harvested chestnut fruits for commercial use. The effect of whey protein isolate–pullulan (WPI–Pul) coating on fresh-roasted chestnuts (FRC) and roasted freeze-dried chestnut (RFDC) quality and shelf life was studied under 2 different storage temperature (4 and 20 °C) conditions. Coatings were formed directly onto the surface of the fruits by dipping them into a film solution. SEM micrographs showed homogeneous WPI–Pul to cover the whole surface of chestnut with good adherence and perfect integrity. Moisture loss or gain, fruit quality, and shelf life were evaluated by weight loss or gain, surface color development, and visible decay during the storage period of 15 to 120 d at 4 and 20 °C, respectively. WPI–Pul coating had a low, yet significant effect on reducing moisture loss and decay incidence of FRC, hence delaying changes in their external color. The results were satisfactory when the coating was done with freeze-drying at low temperature storage, thus improving the quality and increasing the shelf life. This provides an alternative strategy to minimize the significant losses in harvested chestnut.     

Postharvest Aloe vera gel-coating modulates fruit ripening and quality of 'Arctic Snow' nectarine kept in ambient and cold storage

To evaluate the role of Aloe vera gel coating on ripening and fruit quality of nectarine ( Prunus persica L. Batch cv 'Arctic Snow'), the uncoated and coated fruit were allowed to ripen at 20 ± 1 °C in first experiment and in the second experiment, the fruit were stored at 0 ± 0.5 °C and 90 ± 5% RH for 3 and 6 weeks prior to ripening at 20 ± 1 °C. Aloe vera gel-coated fruit kept at ambient or 3 and 6 weeks cold storage reduced respiration rate, ethylene production (62, 37 and 43% respectively), retarded fruit softening, reduced electrolyte leakage (EL), weight loss (65%), levels of ascorbic acid and total antioxidants (24, 9 and 13%) during ripening than control. In conclusion, Aloe vera gel can be used for extending storage life at ambient or cold storage and maintaining quality of 'Arctic Snow' nectarine.