Multi-accelerant approach for rapid shelf-life determination of beverages in polymeric packaging.

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.

Dynamic Thermal Properties Estimation Using Sensitivity Coefficients for Rapid Heating Process.

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.

Mammalian mucosal α-glucosidases coordinate with α-amylase in the initial starch hydrolysis stage to have a role in starch digestion beyond glucogenesis.

Starch digestion in the human body is typically viewed in a sequential manner beginning with α-amylase and followed by α-glucosidase to produce glucose. This report indicates that the two enzyme types can act synergistically to digest granular starch structure. The aim of this study was to investigate how the mucosal α-glucosidases act with α-amylase to digest granular starch. Two types of enzyme extracts, pancreatic and intestinal extracts, were applied. The pancreatic extract containing predominantly α-amylase, and intestinal extract containing a combination of α-amylase and mucosal α-glucosidase activities, were applied to three granular maize starches with different amylose contents in an in vitro system. Relative glucogenesis, released maltooligosaccharide amounts, and structural changes of degraded residues were examined. Pancreatic extract-treated starches showed a hydrolysis limit over the 12 h incubation period with residues having a higher gelatinization temperature than the native starch. α-Amylase combined with the mucosal α-glucosidases in the intestinal extract showed higher glucogenesis as expected, but also higher maltooligosaccharide amounts indicating an overall greater degree of granular starch breakdown. Starch residues after intestinal extract digestion showed more starch fragmentation, higher gelatinization temperature, higher crystallinity (without any change in polymorph), and an increase of intermediate-sized or small-sized fractions of starch molecules, but did not show preferential hydrolysis of either amylose or amylopectin. Direct digestion of granular starch by mammalian recombinant mucosal α-glucosidases was observed which shows that these enzymes may work either independently or together with α-amylase to digest starch. Thus, mucosal α-glucosidases can have a synergistic effect with α-amylase on granular starch digestion, consistent with a role in overall starch digestion beyond their primary glucogenesis function.