ABSTRACT
The fouling of indirect shell and coil heat exchanger by heavy whipping cream (HWC) and non-fat dry milk (NFDM) was studied at aseptic Ultra-High Temperature (UHT) processing conditions (140 °C) using a novel non-intrusive sensor. The sensor emitted a heat pulse intermittently throughout the duration of the process causing an incremental increase in temperature at the tube external surface. The temperature response of the sensor varied due to the radial growth of the fouling layer formed by certain components of the products. Each heating pulse and the temperature response was studied to estimate the thermal conductivity of the fouling layer using inverse problems and parameter estimation. The changes in thermal conductivity were used as an indication of the fouling layer development during food processing at UHT temperatures. The estimated parameters from experimental results showed a decreasing trend in the thermal conductivity of HWC and NFDM from 0.35 to 0.10 and 0.63 to 0.37, respectively. An image analysis tool was developed and used to measure the fouling layer thickness at the end of each trial. The measured thickness was found to be 0.58 ± 0.15 for HWC and 0.56 ± 0.07 mm for NFDM. The fouling layer resistance for HWC and NFDM was 5.95 × 10-3 ± 1.53 × 10-3 and 1.53 × 10-3 ± 2.0 × 10-4 (m2K)/W, respectively.
ABSTRACT
An effective analysis method with multiple accelerant factors is needed for shelf-life determination and prediction for food products with reduced analysis time. Raising the storage temperature is the most common approach utilized in the conventional accelerated shelf-life test (ASLT) to reduce the shelf-life testing time of food. Oxygen pressure as an accelerant for the shelf-life determination of food products has not been given much attention even though it has shown a negative impact on food shelf-life. Combining oxygen pressure and temperature as accelerants has the potential to further reduce the overall analysis time compared to the ASLT. This study focuses on the effects of applying oxygen pressure and temperature as multi-accelerants on the shelf-life of a shelf-stable product by investigating the extent of vitamins degradation and modeling the reaction using a mechanistic approach. A shelf-stable model food fortified with vitamins A, B1, C and D3 was developed to investigate the effect of multiple accelerants on the quality indicators of shelf-stable foods in a polyethylene terephthalate (PET) container. PET bottles filled with model food were placed in a high-pressure (138 kPa) 100% oxygen environment at 40 °C. This novel process is named as the ultra-accelerated shelf-life test (UASLT). Samples were also subjected to ASLT conditions at 40 °C and control condition at 22.5 °C, both at ambient pressure for comparison. UASLT treatment induced a rapid degradation of 27.1 ± 1.9%, 35.8 ± 1.0%, and 35.4 ± 0.7% in vitamins A, C and D3, respectively, in just 50 days. Slower degradation was observed with samples kept under the ASLT conditions for 105 days with a degradation of 24.0 ± 2.0%, 32.0 ± 3.1% and 25.1 ± 1.5% for vitamin A, C and D3, respectively. The control samples that were studied for 210 days showed 14.9 ± 5.0%, 13.8 ± 2.2% and 10.6 ± 0.8% degradation in vitamins A, C and D3, respectively. The increase in the ΔE values due to browning in samples kept at the UASLT, ASLT and control conditions were 11.67 ± 0.09, 7.49 ± 0.19 and 2.51 ± 0.11, respectively. The degradation of vitamin B1 was similar across the treatments. The addition of oxygen pressure significantly increased the degradation reaction rates of the vitamins and color due to the rapid influx of oxygen. A mechanistic model that coupled oxygen diffusion and simultaneous vitamin degradation provided a good fit to the experimental data for the UASLT treatment with a rate constant of 0.686, 0.631 and 0.422 M-1day-1 for vitamins C, D3 and A, respectively. Elevated external oxygen pressure can be used as an accelerant along with moderate temperatures for rapid shelf-life testing of products in polymeric packaging with two-fold reduction in the overall analysis time as compared to ASLT.
Subject(s)
Food Packaging , Food Storage , Food Packaging/methods , Vitamins , Beverages , Vitamin A , OxygenABSTRACT
Simultaneous estimation of thermal properties can be challenging, especially when the parameters are temperature-dependent. Previous research has shown that by using a complementary experiment, temperature-dependent thermal conductivity can be estimated using a single experiment. The objective of this study was to optimize the complementary experiments that can facilitate the simultaneous estimation of temperature-dependent thermal conductivity and volumetric heat capacity. A theoretical study was conducted with two experiments in a single trial with the sample being kept in a cylindrical sample holder, which had a thin film heater in the center. The first part of the experiment was conducted by keeping the external surface temperature at 50 °C for 300 s and allowing the center temperature to equilibrate with the boundary temperature. Then, the second part of the experiment followed, where the thin film heater was supplied with electrical power to increase the center temperate to 140 °C. Several heating profiles were studied to maximize the information obtained from the complementary experiments, and the best one was the power profile with a sinusoidal function. All four parameters of sweet potato puree temperature-dependent thermal conductivity (0.509 to 0.629 W/mK at 25 °C and 140 °C, respectively) and volumetric heat capacity (3.617 × 106 to 4.180 × 106 J/m3K at 25 °C and 140 °C, respectively) were estimated with low standard errors.
ABSTRACT
Disposal of plastic waste has become a widely discussed issue, due to the potential environmental impact of improper waste disposal. Polyethylene terephthalate (PET) packaging accounted for 44.7% of single-serve beverage packaging in the US in 2021, and 12% of global solid waste. A strategic solution is needed to manage plastic packaging solid waste. Major beverage manufacturers have pledged to reduce their environmental footprint by taking steps towards a sustainable future. The PET bottle has several properties that make it an environmentally friendly choice. The PET bottle has good barrier properties as its single-layer, mono-material composition allows it to be more easily recycled. Compared to glass, the PET bottle is lightweight and has a lower carbon footprint in production and transportation. With modern advancements to decontamination processes in the recycling of post-consumer recycled PET (rPET or PCR), it has become a safe material for reuse as beverage packaging. It has been 30 years since the FDA first began certifying PCR PET production processes as compliant for production of food contact PCR PET, for application within the United States. This article provides an overview of PET bottle-to-bottle recycling and guidance for beverage manufacturers looking to advance goals for sustainability.
ABSTRACT
Thermal conductivity determination of food at temperatures > 100 °C still remains a challenge. The objective of this study was to determine the temperature-dependent thermal conductivity of food using rapid heating (TPCell). The experiments were designed based on scaled sensitivity coefficient (SSC), and the estimated thermal conductivity of potato puree was compared between the constant temperature heating at 121.10 °C (R12B10T1) and the rapid heating (R22B10T1). Temperature-dependent thermal conductivity models along with a constant conductivity were used for estimation. R22B10T1 experiment using the k model provided reliable measurements as compared to R12B10T1 with thermal conductivity values from 0.463 ± 0.011 W m-1 K-1 to 0.450 ± 0.016 W m-1 K-1 for 25-140 °C and root mean squares error (RMSE) of 1.441. In the R12B10T1 experiment, the analysis showed the correlation of residuals, which made the estimation less reliable. The thermal conductivity values were in the range of 0.444 ± 0.012 W m-1 K-1 to 0.510 ± 0.034 W m-1 K-1 for 20-120 °C estimated using the k model. Temperature-dependent models (linear and k models) provided a better estimate than the single parameter thermal conductivity determination with low RMSE for both types of experiments. SSC can provide insight in designing dynamic experiments for the determination of thermal conductivity coefficient.