Benchmarking of techniques used to assess the freeze damage in potatoes

Quality deterioration of mashed potatoes during the freeze-thaw cycle: From the perspective of moisture and microstructure

This study aimed to simulate cold chain sales temperatures to predict the effects of temperature fluctuations on the physicochemical properties, moisture distribution, microstructure, and flavor of mashed potatoes. The results showed a decline in the hardness and chewability of mashed potatoes alongside the migration of water from bound water states to weakly bound states under freeze-thaw cycles (FTC) conditions. Microstructural analysis indicated that the adhesive forces between proteins and starch granules were weakened, and the structure of mashed potatoes particles was destroyed following FTC. The oxidation and degradation of fat induced by FTC increased the content of key compounds such as octanal and nonanal, thereby contributing to an overall deterioration in the flavor of mashed potatoes. This study elucidates the effects of FTC on water migration, microstructure, and flavor characteristics of mashed potatoes, thereby providing a theoretical foundation for improving the quality of prefabricated frozen mashed potatoes dishes.

Physico-Chemical Properties and Storage Stability of an Emulsion as a Fat Replacer in Meat Analogs during the Freezing Storage

This study determined the effects of physicochemical and microbial properties of emulsion as a fat replacer in meat analogs during freezing storage. Meat analogs were prepared with different fat replacers: vegetable oil (O) for control, oil in water emulsion (E), and non-emulsified oil in water emulsion (EC) for emulsion control. After that, meat analogs were stored for 0.5, one, three, and six months at −18 °C and −60 °C. The results showed that the drip loss of all samples was not significantly different (p > 0.05). However, the liquid holding capacity of EC and E was significantly higher than that of O (p < 0.05). Additionally, the microstructures of meat analogs of E and EC were smaller with denser pore sizes than O. This explains the significantly lower hardness of E and EC compared to O (p < 0.05). Overall, E showed superior physiochemical and sensory quality. During the storage, the stability of chemical properties, such as volatile basic nitrogen and thiobarbituric acid reactive substances, showed no significant changes (p > 0.05). Moreover, the microbial studies (total viable counts and Escherichia coli count) suggested that meat analogs did not deteriorate during the preparation and storage. Thus, this study suggests that emulsion-type fat replacers influence meat analogs’ physicochemical and sensorial properties. However, these properties are not influenced by the storage temperature and duration.

Effect of isochoric freezing on quality aspects of minimally processed potatoes

The enhanced interest in greater convenience foods has recently led to the expansion of minimally processed potato products. This study investigated the effects of isochoric freezing on pre-peeled potato cubes, including quality attributes (microstructure, texture, and color), nutritional value (ascorbic acid (AA) content, total phenolic content, and antioxidant capacity), and polyphenol oxidase activity. Isochoric freezing (-3 °C/30 MPa) was compared with isobaric freezing (-3 °C/0.1 MPa) and individual quick freezing followed by frozen storage at -20 °C for 4 weeks. The isochoric sample had lower drip loss and volume shrinkage as well as better preserved texture and microstructure than the other samples. All freezing methods caused an increase in total phenolic content and antioxidant capacity, but a decrease in AA content. Also, all freezing methods caused browning of the thawed potatoes, but isochoric freezing delayed its onset for more than 1 week. PRACTICAL APPLICATION: Results showed that isochoric freezing of pre-peeled and cut potatoes caused less freeze damage than isobaric and individual quick freezing, which might find application in the commercial preservation of minimally processed food products.