Phytonutrients and Metabolism Changes in Topped Radish Root and Its Detached Leaves during 1 °C Cold Postharvest Storage

Glucosinolates, lipid-soluble vitamins E and K contents, primary metabolites and plant hormones were analyzed from topped radish root and detached leaf during storage at 1 °C. The topped root was analyzed at 0, 5, 15, 30, and 90 days after storage while the detached leaf was analyzed at 0, 5, 15, 30, and 45 days in an airtight storage atmosphere environment. The results showed that aliphatic glucosinolates were gradually decreased in leaf but not in root. There was a highly significant correlation between tryptophan and 4-methoxyindoleglucobrassicin in both tissues (r = 0.922, n = 10). There was no significant difference in vitamins E and K in leaf and root during storage. Plant hormones partially explained the significantly changed metabolites by tissue and time, which were identified during cold storage. Phenylalanine, lysine, tryptophan, and myo-inositol were the most important biomarkers that explained the difference in leaf and root tissue during cold storage. The most different metabolism between leaf and root tissue was starch and sucrose metabolism. Therefore, different postharvest technology or regimes should be applied to these tissues.

Seasonality, shelf life and storage atmosphere are main drivers of the microbiome and E. coli O157:H7 colonization of post-harvest lettuce cultivated in a major production area in California

Background Lettuce is linked to recurrent outbreaks of Shiga toxin-producing Escherichia coli (STEC) infections, the seasonality of which remains unresolved. Infections have occurred largely from processed lettuce, which undergoes substantial physiological changes during storage. We investigated the microbiome and STEC O157:H7 (EcO157) colonization of fresh-cut lettuce of two cultivars with long and short shelf life harvested in the spring and fall in California and stored in modified atmosphere packaging (MAP) at cold and warm temperatures. Results Inoculated EcO157 declined significantly less on the cold-stored cultivar with short shelf life, while multiplying rapidly at 24 °C independently of cultivar. Metagenomic sequencing of the lettuce microbiome revealed that the pre-storage bacterial community was variable but dominated by species in the Erwiniaceae and Pseudomonadaceae. After cold storage, the microbiome composition differed between cultivars, with a greater relative abundance (RA) of Erwiniaceae and Yersiniaceae on the cultivar with short shelf life. Storage at 24 °C shifted the microbiome to higher RAs of Erwiniaceae and Enterobacteriaceae and lower RA of Pseudomonadaceae compared with 6 °C. Fall harvest followed by lettuce deterioration were identified by recursive partitioning as important factors associated with high EcO157 survival at 6 °C, whereas elevated package CO2 levels correlated with high EcO157 multiplication at 24 °C. EcO157 population change correlated with the lettuce microbiome during 6 °C storage, with fall microbiomes supporting the greatest EcO157 survival on both cultivars. Fall and spring microbiomes differed before and during storage at both temperatures. High representation of Pantoea agglomerans was a predictor of fall microbiomes, lettuce deterioration, and enhanced EcO157 survival at 6 °C. In contrast, higher RAs of Erwinia persicina, Rahnella aquatilis, and Serratia liquefaciens were biomarkers of spring microbiomes and lower EcO157 survival. Conclusions The microbiome of processed MAP lettuce evolves extensively during storage. Under temperature abuse, high CO2 promotes a lettuce microbiome enriched in taxa with anaerobic capability and EcO157 multiplication. In cold storage, our results strongly support a role for season and lettuce deterioration in EcO157 survival and microbiome composition, suggesting that the physiology and microbiomes of fall- and spring-harvested lettuce may contribute to the seasonality of STEC outbreaks associated with lettuce grown in coastal California.

Application of air ionization in refrigerant storage of grapes refuse, boiled with starch syrup, in marshmallow technology

Experimental data on the change in the number and species composition of microorganisms in the atmosphere have been provided. These includes the changes on the walls of refrigeration chambers and on the surface of berries of the grape varieties Preobrazhenie and Livia when stored in a refrigerating chamber with a normal and ionized atmosphere. It was shown that the use of an ionized atmosphere with a concentration of positive aeroions of 0.25… 0.48 × 1 × 103 cm3 and negative aeroions of 0.11… 0.25 × 1 × 103 cm3 helped to reduce the overall microbiota contamination in a storage atmosphere by 94.7%. This happened on the surface of the walls and structures of the refrigerating chamber by 100% and on the surface of berries of the grape varieties Preobrazhenie and Livia by 95.6% and 97.1%, respectively.

Hypobaric Storage of Representative Root, Leaf, Fruit, and Flower Tissues: Comparisons to Storage at Atmospheric Pressure and Normoxia

Hypobaric or low-pressure storage (LPS) is a technology that has been reported to have significant potential to preserve fresh produce quality. However, excessive moisture loss has often been erroneously reported to limit the utility of LPS. We report on hypobaric (1.6 to 2.0 kPa) storage of representative bulky and leafy fruits and vegetables {strawberry (Fragaria ×ananassa Duchesne ex Rozier) fruit, carrot [Daucus carota subsp. sativus (Hoffm.) Arcang.] roots, spinach (Spinacia oleracea L.) leaves, and rose (Rosa ×hybrida ‘Attaché Pink’) flowers} using a laboratory-scale LPS and provide data on the regulation of humidity and temperature and describe effects on moisture loss and quality. The LPS achieved near saturation (>99.5%) of water without condensation on the chamber sidewalls. This required tight regulation of the chamber wall temperature (2.2 °C ± 0.15 °C) and careful control of the flux of air into the chamber. The rate of moisture loss was unaffected by the pressure of the storage atmosphere; however, it was affected by commodity, being lower for strawberry than for carrot or spinach, and averaging 0.08%, 0.40%, and 0.35% per day, respectively (average of normal and low pressure combined). Moisture loss of long-stemmed rose in LPS averaged 0.071% per day over an 8-week storage period. Although moisture loss was low, the LPS environment appeared to enhance water loss from deeper within plant tissues than storage at atmospheric pressure and, in roses, resulted in bent neck 2 or 3 days after removal from storage after 3 weeks. For this reason, LPS did not benefit storability of cut ‘Attaché Pink’ roses compared with high-humidity chambers maintained at atmospheric pressure.

Effect of 1-Methylcyclopropene (1-MCP) and Storage Atmosphere on the Volatile Aroma Composition of Cloudy and Clear Apple Juices

The effects of 1-methylcyclopropene (1-MCP), storage atmosphere (controlled (CA) or regular (RA)), and juice processing (clear or cloudy) on the volatile aroma compounds from McIntosh and Honeycrisp apples following 4-month storage were studied. All the major esters, aldehydes, and total volatile content from McIntosh juice were significantly affected by the two-way interaction between harvest maturity and 1-MCP treatment (p ≤ 0.01), as well as harvest maturity and storage atmosphere (p ≤ 0.001). In McIntosh juices, a remarkable reduction of all types of esters, aldehydes, most alcohols, and total volatile compounds was found when juices were prepared from 1-MCP-treated apples. In Honeycrisp, significant differences in the level of esters and the total volatile aroma was caused by storage atmosphere and juice processing techniques (p ≤ 0.001), but not by 1-MCP treatment. As compared to clear juices, cloudy juice samples from Honeycrisp had a considerably higher content of total volatiles, esters, and aldehydes.