Comparing steady-state to unsteady-state respiration rate measurement methods for design of modified atmosphere packaging of grape tomatoes and blueberries with microperforations.

Designing modified atmosphere packages (MAPs) for fresh produce requires respiration rate (RR) data. A steady-state (SS) approach is widely used but is expensive, tedious, and time-consuming. Unsteady-state (USS) methods mitigate shortcomings of the SS approach, but comparisons between the two approaches have not been done to verify the design outcomes of MAPs, especially those with microperforations. RR measurement methods for grape tomatoes and blueberries were compared. Data were then used to design microperforated MAP packages to compare predicted design specifications created from RR data with observed shelf life. Results show that the USS method provides similar magnitudes of RR and predicts similar numbers of perforations as the SS method. Observations of packages produced using 100 µm perforations, using measured respiration data, suggest that both methods underestimated what might have been deemed correct by about one microperforation. PRACTICAL APPLICATION: Designing packaging for fresh produce requires the knowledge of produce respiration. Steady-state methods are conceptually simple, but time-consuming. Unsteady-state methods are rapid. This work compares methods on design of packages.

Effect of pH on lipid oxidation of red onion skin extracts treated with washed tilapia (Oreochromis niloticus) muscle model systems.

The aim of the study was to investigate the effect of pH on the lipid oxidation of red onion skin extracts (ROSEs) treated with washed tilapia muscle model systems (WTMS). Minced and buffered washed samples were prepared at pH 6.3 and 6.8. The WTMS were treated with2 different concentrations of red onion skin prior to storage for 5 days. Lipid oxidation was investigated via peroxide values (PVs), thiobarbituric acid reactive substances (TBARS), and the formation of volatile compounds. Fatty acid profiles of the samples were also identified. The ROSEs were able to significantly suppress the PV (~71%) and TBARS (~42%) formation. Hexanal and octanal formations in the WTMS were relatively less in the ROSE-treated samples. The WTMS samples prepared at pH 6.3 were more vulnerable to lipid oxidation than those prepared at pH 6.8. Red onion skin polyphenols may increase the lag phase of lipid oxidation, depending on pH levels, resulting in the shelf life extension of raw fish.

Permeable Gas Cavity at Elevated Pressure Enhances Modified Atmosphere Packaging of Fresh Produce.

Modified atmosphere packaging (MAP) of fresh produce involves exploiting package properties to satisfy respiration activity of produce. While effective, package material properties are not infinitely adjustable to match needs of all products. Additional ways of providing favorable in-package gaseous environments are needed. This work explores the use of permeable inserts filled with gas at elevated pressures as a means to achieve in-package gaseous atmospheres that may not be possible by the package alone. Mathematical models were developed to predict transient package atmospheres for packages containing respiring produce and pressurized permeable inserts. The model was validated for semirigid tray packages containing grape tomatoes and Granny Smith apples. With inserts initially pressurized with oxygen at approximately 200 to 300 kPa (about 30 to 45 psi), about 2 weeks additional shelf life was observed relative to controls for both tomatoes and apples in test packages. Additionally, simulations provide design guidance for pressurized inserts for the case of very high respiration rate produce such as spinach. PRACTICAL APPLICATION: This work promises to expand application of modified atmosphere packaging (MAP). Currently, applications are limited by gas transfer material properties of existing packaging films. However, packaging offers other important functions that may not be well served by materials that satisfy critical gas permeation requirements. This work demonstrates an approach that disconnects packaging material specifications from MAP design.

Measuring and predicting head space pressure during retorting of thermally processed foods.

UNLABELLED: Traditional metal cans and glass jars have been the mainstay in thermally processed canned foods for more than a century, but are now sharing shelf space with increasingly popular flexible pouches and semi-rigid trays. These flexible packages lack the strength of metal cans and glass jars, and need greater control of external retort pressure during processing. Increasing internal package pressure without counter pressure causes volumetric expansion, putting excessive strain on package seals that may lead to serious container deformation and compromised seal integrity. The primary objective of this study was to measure internal pressure build-up within a rigid air-tight container (module) filled with various model food systems undergoing a retort process in which internal product temperature and pressure, along with external retort temperature and pressure, were measured and recorded at the same time. The pressure build-up in the module was compared with the external retort pressure to determine the pressure differential that would cause package distortion in the case of a flexible package system. The secondary objective was to develop mathematical models to predict these pressure profiles in response to known internal temperature and initial and boundary conditions for the case of the very simplest of model food systems (pure water and aqueous saline and sucrose solutions), followed by food systems of increasing compositional complexity (green beans in water and sweet peas in water). Results showed that error between measured and predicted pressures ranged from 2% to 4% for water, saline, and green beans, and 7% to 13% for sucrose solution and sweet peas. PRACTICAL APPLICATION: Flexible packages have limited strength, and need more accurate and closer control of retort pressure during processing. The package becomes more flexible as it heats and might expand with increasing internal pressure that may cause serious deformation or rupture if not properly controlled and/or counterbalanced with external retort pressure. This article describes methods for determining exactly what the retort pressure profile will need to be to avoid this problem during retorting, and mathematical models to predict these pressures in response to known internal temperature and initial/boundary conditions.

The impact of packaging materials on the antioxidant phytochemical stability of aqueous infusions of green tea (Camellia sinensis) and yaupon holly (Ilex vomitoria) during cold storage.

Ready to drink (RTD) teas are a growing segment in the beverage category, brought about by improvements in the flavor of these products and healthy market trends driven by consumers. The presented results evaluated the antioxidant phytochemical stability of RTD teas from aqueous infusions of traditional green tea (Camellia sinensis) and a botanical tea from yaupon holly (Ilex vomitoria) as influenced by packaging materials during cold storage. Two common packaging materials for RTD products are glass and polyethylene terephthalate (PET) and have been compared to a retortable pouch (RP), an emerging packaging material for various types of food since it is durable, inexpensive, lightweight, and easy to sterilize. Storage stability was then evaluated for each aqueous infusion prepared at 10 g/L at 90 °C for 10 min and evaluated at 3 °C in the absence of light over 12 weeks. Analyses included quantification and characterization of individual polyphenolics by high-performance liquid chromatography-photodiode array and liquid chromatography-electrospray ionization-mass spectrometry as well as changes in total antioxidant capacity. For green tea, concentrations of the three major flavan-3-ols, epigallocatechin gallate, epigallocatechin, and epicatechin gallate were better retained in glass bottles as compared to other packages over 12 weeks. In yaupon holly, chlorogenic acid and its isomers that were the predominant compounds were generally stable in each packaging material, and a 20.6-fold higher amount of saponin was found as compared to green tea, which caused higher stability of flavonol glycosides present in yaupon holly during storage. The antioxidant capacity of green tea was better retained in glass and PET versus RP, whereas no differences were again observed for yaupon holly. Results highlight the superiority of oxygen-impervious glass packaging, but viable alternatives may be utilizable for RTD teas with variable phytochemical compositions.