Molecular Dynamics and Structure in Physical Properties and Stability of Food Systems

Application of state diagrams to understand the nature and kinetics of (bio)chemical reactions in dry common bean seeds: A scientific guide to establish suitable postharvest storage conditions

Storage is a fundamental part of the common bean postharvest chain that ensures a steady supply of safe and nutritious beans of acceptable cooking quality to the consumers. Although it is known that extrinsic factors of temperature and relative humidity (influencing the bean moisture content) control the cooking quality deterioration of beans during storage, the precise interactions among these extrinsic factors and the physical state of the bean matrix in influencing the rate of quality deteriorative reactions is poorly understood. Understanding the types and kinetics of (bio)chemical reactions that influence the cooking quality of beans during storage is important in establishing suitable storage conditions to ensure quality stability. In this review, we integrate the current insights on glass transition phenomena and its significance in describing the kinetics of (bio)chemical reactions that influence the cooking quality changes during storage of common beans. Furthermore, a storage stability map based on the glass transition temperature of beans as well as kinetics of the main (bio)chemical reactions linked to cooking quality deterioration during storage was designed as a guide for determining appropriate storage conditions to ensure cooking quality stability.

Effect of larval nutrition on the hemolymph protein composition during metamorphosis of Anastrepha obliqua

Few studies have focused on how nutrition affects the bioavailability and investment of protein during the metamorphosis of tephritids. Our study allowed us to observe how the type and particle size of the bulking agent affected the protein composition in the hemolymph of the larva and adult of Anastrepha obliqua. Results indicated that, true protein bioavailability and protein profile was greatly modified by the bulking agent and its particle size. The physical structure of the food matrix affected the content of crude fiber (F), crude protein (P), F/P ratio, non-protein nitrogen, ammoniacal nitrogen, and α-amylase and trypsin inhibitors. Results from SDS-PAGE revealed 45 fractions with well-defined bands ranging from ~28 to ~401 kDa in larvae and adults, we found the main differences between the samples from different food matrices within the 75-100 kDa range. Hemolymph of adults from the coarse coconut fiber food matrix treatment showed a single band with a molecular weight close to 250 kDa, probably associated with a storage protein such as lipophorins. The food matrix with a coarse bulking agent had a high concentration of ammoniacal nitrogen, suggesting high microbial activity. In conclusion, the particle size of the bulking agent of the food matrix changes the bioavailability of protein in hemolymph in the adult regardless of the total concentration of protein. Also, when the particle size of the bulking agent favored the F/P ratio, higher larval density resulted in higher individual larval weight, larval yield, and adult emergence.

Natural Food Colorants and Preservatives: A Review, a Demand, and a Challenge

The looming urgency of feeding the growing world population along with the increasing consumers' awareness and expectations have driven the evolution of food production systems and the processes and products applied in the food industry. Although substantial progress has been made on food additives, the controversy in which some of them are still shrouded has encouraged research on safer and healthier next generations. These additives can come from natural sources and confer numerous benefits for health, beyond serving the purpose of coloring or preserving, among others. As limiting factors, these additives are often related to stability, sustainability, and cost-effectiveness issues, which justify the need for innovative solutions. In this context, and with the advances witnessed in computers and computational methodologies for in silico experimental aid, the development of new safer and more efficient natural additives with dual functionality (colorant and preservative), for instance by the copigmentation phenomena, may be achieved more efficiently, circumventing the current difficulties.

Microstructural and chemical properties of gari and eba: Food products from cassava (Manihot esculenta Cranz)

The microstructure, elemental distribution and rheological behavior of two varieties of gari and their doughs (eba) were investigated. SEM analysis revealed a concave structure with fibre-strands, which were altered after processing to eba. Gari nanostructures which were analyzed with TEM were not affected when processed to eba. SEM-EDX microanalysis revealed the presence of magnesium, potassium, calcium, manganese, iron, and cobalt for both varieties, which were altered after processing. Rheological analysis revealed increases in storage modulus, with concomitant loss factor for both varieties. Their viscosity decreased with increasing shear rate. GC-MS analysis revealed the presence of sugar, fatty acids, and steroids in both varieties, which were also affected after processing. Both varieties showed significant free radical scavenging activity which was not affected after processing. These results indicate that the conclave microstructure, elements and phytochemicals of both gari varieties are altered after processing to eba, with their nanostructure and antioxidant activity unaltered.

The kinetics of ageing in dry-stored seeds: a comparison of viability loss and RNA degradation in unique legacy seed collections

BACKGROUND AND AIMS

Determining seed longevity by identifying chemical changes that precede, and may be linked to, seed mortality, is an important but difficult task. The standard assessment, germination proportion, reveals seed longevity by showing that germination proportion declines, but cannot be used to predict when germination will be significantly compromised. Assessment of molecular integrity, such as RNA integrity, may be more informative about changes in seed health that precede viability loss, and has been shown to be useful in soybean.

METHODS

A collection of seeds stored at 5 °C and 35-50 % relative humidity for 1-30 years was used to test how germination proportion and RNA integrity are affected by storage time. Similarly, a collection of seeds stored at temperatures from -12 to +32 °C for 59 years was used to manipulate ageing rate. RNA integrity was calculated using total RNA extracted from one to five seeds per sample, analysed on an Agilent Bioanalyzer.

RESULTS

Decreased RNA integrity was usually observed before viability loss. Correlation of RNA integrity with storage time or storage temperature was negative and significant for most species tested. Exceptions were watermelon, for which germination proportion and storage time were poorly correlated, and tomato, which showed electropherogram anomalies that affected RNA integrity number calculation. Temperature dependencies of ageing reactions were not significantly different across species or mode of detection. The overall correlation between germination proportion and RNA integrity, across all experiments, was positive and significant.

CONCLUSIONS

Changes in RNA integrity when ageing is asymptomatic can be used to predict onset of viability decline. RNA integrity appears to be a metric of seed ageing that is broadly applicable across species. Time and molecular mobility of the substrate affect both the progress of seed ageing and loss of RNA integrity.

Variation of desiccation tolerance and longevity in fern spores

This work contributes to the understanding of plant cell responses to extreme water stress when it is applied at different intensity and duration. Fern spores are used to explore survival at relative humidity (RH)<85% because their unicellular nature eliminates complexities that may arise in multicellular organisms from slower drying and variable responses of different cell types. Fern spore cytoplasm solidifies between 30 and 60% RH and spores survive this transition, but subsequently lose viability. We characterized the kinetics of viability loss in terms of the fluid to solid transition using concepts of water activity (i.e., sorption) and glass transition (Tg), two concepts that dominate studies of food and pharmaceutical stability. For all fern species studied, longest survival times were observed in spores placed at about 10-25% RH and mortality rates increased sharply above and below this moisture level. A RH of 10-25% corresponds well to sorption behavior parameters and is below the glass transition, measured using differential scanning calorimetry. Though response to RH was similar among species, the kinetics of deterioration varied considerably among species and this implies differences in the structure or mobility of molecules within the solidified cytoplasm. Our work suggests that desiccation damage occurs in desiccation tolerant cells, and that it is expressed as a time-dependent response, otherwise known as aging.