Postharvest shelf life extension of minimally processed kale at ambient and refrigerated storage by use of modified atmosphere.

Kale is becoming an important vegetable worldwide, mainly due to its nutritional properties. Kale leaves can be marketed whole, although minimal processing is also in demand. In this article, it was analyzed the effect of packaging in a modified atmosphere of fresh-cut kale leaves stored at 20 °C and 4 °C. Kale leaves were cut into 4 × 4 cm strips and stored in low-density polyethylene bags. Samples processed in the same way but stored in PVC were used as controls. Leaves kept in a modified atmosphere showed a delay in color change with Hue values from about 130 to 120 under PMA against 130 to 100 in control group (CTR) leaves. Chlorophyll degradation was also delayed in both storage temperatures. Samples stored under PMA showed about two times the levels of total chlorophylls with respect to CTR samples at the end of the storage. No changes in total sugar content were detected during storage and no differences were detected between control and modified atmospheres stored samples. Samples maintained in a modified atmosphere showed a lower decrement in soluble proteins and a lower rate of RUBISCO degradation at both temperatures. The relation of RUBISCO content PMA/CTR ranged from 1 to about 3 toward the end of storage No changes in phenols content were found when comparing control and treated samples. However, flavonoid and the antioxidant contents increased in samples stored in modified atmospheres with respect to their controls. We demonstrated that storage in modified atmospheres could be an adequate and simple methodology to extend postharvest life of this minimally processed product at both ambient and refrigerated storage.

Evidence of glucosinolates translocation from inflorescences to stems during postharvest storage of broccoli.

Broccoli is a vegetable appreciated by consumers for its nutritional properties, particularly for its high glucosinolate (GLS) content. However, broccoli shows a high rate of senescence during postharvest and the GLS content in inflorescences decreases sharply. Usually, postharvest studies on broccoli focus on inflorescences, ignoring the other tissues harvested such as the stems and main stalk. In this work, GLS metabolism in whole heads of broccoli (including inflorescences, small stems and stalk) was analysed during postharvest senescence. The content of GLS content, expression of GLS metabolic genes, and expression of GLS transport-associated genes were measured in the three parts of harvested broccoli. A marked decrease in the content of all GLSs was detected in inflorescences, but an increase in the stems and stalk. Also, decreased expressions of GLS biosynthesis and degradation genes were detected in all tissues analysed. On the other hand, an increase in the expression of one of the genes involved in GLS transport was observed. These results suggest that GLSs would be transported from inflorescences to stems during postharvest senescence. From a commercial point of view, broccoli stems are usually discarded and not used as food. However, the accumulation of GLSs in the stems is an important factor to consider when contemplating potential commercial use of this part of the plant.

Effect of Aloe vera gel coating on organoleptic and nutritional quality of minimally processed carrot.

Demand for fresh vegetables has led to development studies in postharvest area mainly focused on minimizing and look for alternatives to chemical additives for food preservation. The use of natural derived edible coatings emerges as a promising alternative for maintaining quality of vegetables. The objective of this study was to evaluate the effect of Aloe vera gel in minimally processed carrot during postharvest storage. Samples with different degrees of processing were immersed in Aloe vera gel, packaged polyolefin bags, and stored in refrigerated chambers at 5 °C for 12 days. Different organoleptic and quality parameters were evaluated. In general, the samples treated with Aloe vera gel showed less quality loss and a lower increment in the bleaching index. Moreover, sensory analysis allowed to establish that carrots processed in slices and shredded and coated with the gel had a more flavorful taste and higher moisture content. Aloe vera treatment did not influence the microbiological growth of bacteria and fungi during storage. Regarding nutritional quality, the treated samples showed a higher accumulation or lower degradation of phenols, flavonoids, and carotenoids, probably generating in this way, a higher antioxidant capacity in these samples. Finally, Aloe vera gel treatment did not influence sugar dynamics in any of the samples. It can be concluded that the treatment with Aloe vera gel allows maintaining a better organoleptic and nutritional quality of carrots with different degrees of processing during refrigerated storage.

Harvesting at different time-points of day affects glucosinolate metabolism during postharvest storage of broccoli.

The consumption of broccoli provides a large quantity of compounds with nutraceutical properties to the human diet. Broccoli has a high content of glucosinolates, compounds of the specialized metabolism with anticarcinogenic activity. In a previous work, we found that harvesting different time-points during the day affects the rate of senescence of broccoli heads during postharvest storage. In this work, we tested the same cultural practice to evaluate glucosinolate content and expression of genes involved in glucosinolate metabolism. Broccoli heads were harvested at 8:00, 13:00 and 18:00 h and stored for 5 d at 20 °C in darkness. We found that content and composition of the glucosinolate pool was affected by the time of harvest. Levels of indolic glucosinolates decreased with the time of harvest on the day whereas indolic glucosinolate showed only a moderate decrease. The expression of genes associated to the biosynthesis of aliphatic glucosinolates was variable during the day. In relation to indolic glucosinolates, an increase in the expression of the transcription factor BolMYB51 was detected around 13:00 h, which strongly correlated with the increase in expression of genes associated to their biosynthesis towards the end of the day. During postharvest, the storage in darkness affected differently the metabolisms of indolic and aliphatic glucosinolates. The content of aliphatics decreased during the postharvest period, as well as the expression of the genes associated with their biosynthesis. In contrast, in the case of indolics, their content remained constant or varied slightly, while the expression of the associated biosynthetic genes decreased only slightly. Finally, the genes related to the degradation of glucosinolates appeared to be strongly regulated by light conditions, since their expression increased during the course of the day and decreased markedly during postharvest storage in darkness. These results suggest that harvesting of broccolis close to noon would be convenient to maintain higher levels of glucosinolates during postharvest storage.

The time of the day to harvest affects the degreening, antioxidant compounds, and protein content during postharvest storage of broccoli.

Harvesting of broccoli at several moments of the day affects the rate of senescence during storage. In this work, broccoli heads were harvested at several moments and then kept at 20°C in order to analyze protein metabolism and antioxidant compounds. Almost no differences were detected in the contents of total and soluble proteins, and free amino acids. Only an increment in free amino acids was detected by day 3 in samples obtained at 8:00 hr. With reference to antioxidants, the contents of ascorbic acid, carotenoids and xanthophylls, phenols, and flavonoids were similar in samples harvested at different moments. However, an increment was detected in carotenoids, phenols, and flavonoids during storage of samples collected at 18:00 hr on day 3 and samples collected at 13:00 hr on day 5. The combination of delay of senescence and increment in antioxidants suggest harvesting at 12:00 or 18:00 hr. PRACTICAL APPLICATION: Broccoli is a vegetable with an important level of nutrients. However, it is also highly perishable and suffers a high rate of senescence and loss of quality during postharvest. In this work, it is demonstrated that the simple practice of harvests in different moments of the day can affect the postharvest behavior of broccoli, and it is suggested to carry out the harvest toward the end of the day.