Stability of vitamin C, color, and garlic aroma of garlic mashed potatoes in polymer packages processed with microwave-assisted thermal sterilization technology

The U.S. Army and NASA need ready-to-eat meals with extended shelf-life for military operations and future manned space missions. For traditional heat sterilization methods, aluminum foil laminated pouches are used to achieve a shelf-life of 3 to 5 years at room temperature. However, those packages are not suited for advanced thermal processing technologies based on microwave energy. This research investigated the effect of polymeric packaging materials on storage stability of garlic flavor, vitamin C, and color of garlic mashed potatoes processed with microwave-assisted thermal sterilization (MATS) technology. Three types of high-barrier metal oxide-coated polymer pouches were used for MATS process, designed to achieve lethality approximately F₀ = 6 min. Aluminum foil-based pouches were used for retort process as control. Results demonstrated that both oxygen and water vapor barrier properties (oxygen transmission rate [OTR] and water vapor transmission rate [WVTR]) of the polymer pouches were affected by MATS processing. OTR increased by three to nine times, while WVTR increased by 5 to 20 times after processing. The MATS process resulted in 13% to 16% vitamin C loss, while retort process resulted in 18% loss in garlic mashed potato. The kinetics of vitamin C indicated that metal oxide-coated high-barrier packages (after processing OTR <0.1 cc/m² .day; WVTR <1.0 g/m² .day) could replace aluminum foil-based pouches for MATS processed shelf-stable ready-to-eat garlic mashed potatoes. PRACTICAL APPLICATION: Garlic mashed potatoes in polymer packages processed in a microwave-assisted thermal sterilization (MATS) system had better retention of vitamin C compared to samples packaged in aluminum laminated pouches and processed in retort. Polymer packages combined with MATS processing could potentially provide safe, better quality, and nutritious shelf-stable food products for military and space missions.

Natural color pigments: oxidative stability and degradation kinetics during storage in thermally pasteurized vegetable purees

BACKGROUND

Package oxygen transmission rate (OTR) can affect the stability of natural color pigments such as anthocyanins, betalains and chlorophylls in foods during storage. In the present study, we investigated the oxygen sensitivity of selected pigments in thermally pasteurized vegetable purees held at a refrigeration temperature. We modulated the oxygen ingress in packaging using multilayer films with OTRs of 1, 30 and 81 cm3  m-2  day-1 . Red cabbage, beetroot and pea purees were vacuum packed, pasteurized to achieve a cumulative lethality ofP 90 ° C 10 ° C = 12.8-13.4 min and stored at 7 °C for 80 days.

RESULTS

Anthocyanins were relatively stable (< 4% losses), regardless of the film OTR. Betalains showed the highest sensitivity to different OTRs, with total losses varying from 4% to 49% at the end of storage and showing significant differences (P < 0.05) among the three films. Chlorophylls showed no significant difference (P > 0.05) in sensitivity to film OTRs. However, continuous degradation of chlorophylls was observed for all film types, with total chlorophyll losses ranging from 33% to 35%. Overall color differences (ΔE) at the end of storage for cabbage, beet and pea puree were between 0.50-1.70, 1.00-4.55 and 7.41-8.08, respectively. Betalains and chlorophylls degradation followed first-order and fractional conversion kinetics, whereas ΔE followed zero-order and fractional conversion kinetics during storage.

CONCLUSION

All three pigments behaved differently to oxygen ingress during storage. Low to medium barrier films are suitable for products containing red cabbage anthocyanins. High barrier films are must for betalains, whereas medium to high barrier films are suitable for chlorophyll-containing products. © 2019 Society of Chemical Industry.