Gustavo Martínez

Broccoli (Brassica oleracea L. var. Italica) is a rich source of glucosinolates, bioactive compounds whose levels are markedly affected by postharvest senescence. The present study evaluated the effects of hormonal regulators associated with senescence—cytokinins, ethylene, and the ethylene-action inhibitor 1-methylcyclopropene (1-MCP)—on glucosinolate metabolism during postharvest storage of broccoli heads. Broccoli heads were treated with 6-benzylaminopurine (BAP), ethephon, or 1-MCP and stored at 20 °C for five days in darkness. Senescence progression was evaluated through superficial color and chlorophyll content. Glucosinolate pattern and gene expression involved in glucosinolate biosynthesis and degradation was also analyzed. Postharvest storage induced rapid yellowing, chlorophyll loss, and a general decline in glucosinolate content in control samples. BAP and 1-MCP treatments significantly delayed senescence, preserved chlorophyll levels, and reduced glucosinolate losses, particularly for indolic glucosinolates such as glucobrassicin and neoglucobrassicin. In the case of BAP-treated samples, glucobrassicin and neoglucobrassicin contents were 117% and 93% higher, respectively, compared to the controls on day 5. In the case of 1-MCP-treated samples, greater differences were detected on day 3, with glucobrassicin and neoglucobrassicin levels 69% and 66% higher, respectively. In contrast, ethephon accelerated senescence and promoted a more pronounced decrease in both aliphatic and indolic glucosinolates. Gene expression analyses showed a general downregulation of aliphatic glucosinolate biosynthetic genes during storage, whereas indolic pathway genes exhibited hormone-dependent responses. Overall, the results indicate that senescence-associated hormonal regulation plays a central role in glucosinolate metabolism during broccoli postharvest storage, and that BAP and 1-MCP treatments are effective strategies to maintain nutritional quality by delaying senescence and glucosinolate degradation.

Lilies are commonly grown and marketed as cut flowers. Harvesting causes considerable stress, which triggers accelerated senescence, making this process a limiting factor of their postharvest life. Senescence control is achieved through various methodologies, including moderate-temperature thermal treatments for a short time. These treatments cause mild stress that can affect the tissues metabolism. This study aimed to determine the quality, postharvest life, and metabolism of Lilium longiflorum after applying thermal stress to the base of the flower stems. Heat treatments were performed by using hot water (50 °C during 5 min) in the first 2 cm above the cut on the stalk, while a similar treatment was carried out with water at 20 °C for the controls. The treated stems showed less weight loss and water consumption; but the buds opened later. Similarly, less senescence and chlorophyll loss were observed in the leaves of the treated samples. A trend towards a higher concentration of phenols was observed in the first days of storage in the leaves and tepals of the treated stems, no significant variations in flavonoid content were detected. Lower amounts of TBARS and less electrolyte loss were detected in the heat-treated samples, indicating less peroxidation and greater membrane stability. The treatment also induced higher anthocyanin accumulation in tepals. The results suggest that the hot water thermal treatment in postharvest is an appropriate method to improve stem freshness, bud opening degree, and delay senescence, prolonging vase life without negative effects during storage.

Broccoli is a vegetable with a growing consumer demand worldwide due to its important nutritional properties, including high amounts of glucosinolates. However, this vegetable has a short postharvest life and quickly loses its organoleptic and nutritional quality. Modified atmosphere is one of the numerous methodologies used to delay deterioration during postharvest storage of broccoli heads. In this study, the effect of a modified atmosphere during postharvest storage of broccoli on glucosinolate metabolism was evaluated. Five glucosinolates were identified by using a UPLC system coupled to a mass spectrometer. We detected one aliphatic glucosinolate and four indolic glucosinolates, and their concentration was found to decrease during storage. The decrease in content was less marked, and in some cases, an increased level was observed in the treated samples. Moreover, the treatment made it possible to maintain higher expression (analyzed by real-time quantitative PCR) of genes linked to glucosinolate biosynthesis. We also detected an increased expression of some genes related to indolic glucosinolate biosynthesis. Overall, storage of broccoli in modified atmospheres allowed for maintaining better visual quality and higher levels of glucosinolates.

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.

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.

The aim of this work was to improve the understanding about the relationship between solar radiation and temperature exposure during crop and tomato fruit susceptibility to postharvest chilling injury. Two preharvest treatments were applied: direct sunlight exposed plants (Ex) and shaded plants (Sh). After harvest, fruit were stored at 10⁰C and 4⁰C for ten days. Then, fruit were removed from the chambers and stored at room temperature for four days. Several determinations were carried out: total mineral and calcium content, fruit quality and postharvest parameters, ions leakage and thiobarbituric acid reactive species content and chilling injury index (CII). Ex fruit had higher values of chilling injury index than the Sh fruit, and at the same time, fruit under 4⁰C storage treatment presented a more marked damage than those stored at 10⁰C, demonstrating that accumulated radiation in the field, as a result of a higher solar radiation exposure, is a critical factor affecting postharvest chilling injury susceptibility. The lower calcium content in the Ex fruit could be one of the causes of their response to chilling.

Broccoli contains a high content of nutraceutical compounds, such as glucosinolates and flavonoids. In this work, the effect of different treatments that modulate postharvest senescence of broccoli was evaluated and flavonoid metabolism during postharvest storage was analyzed at 20°C. A decrease in hue angle (HUE°) and chlorophylls and an increase in flavonoid content were detected during senescence. It observed that most of the treatments that delayed senescence also decreased flavonoid content, except visible light and UV-C treatments. In all cases, a direct correlation between those treatments that increased flavonoid biosynthesis and BoPAL gene expression was detected. This response was not detected in the expression of the other two flavonoid synthesis relevant genes BoCHS and BoCHI, suggesting that BoPAL has a greater influence on the regulation of the via, during broccoli senescence. Practical applications Broccoli is a vegetable with valuable nutritional properties. Because it is in full development at the time of harvest, it has a short shelf life. In this work, it is showed that visible light and UV-C treatments not only delayed the senescence of broccoli, but also increased flavonoid content. Our results suggest that the most important enzyme in the phenylpropanoid biosynthesis pathway during broccoli postharvest is phenylalanine ammonia lyase, and that this may be a key point in regulating the biosynthesis of these nutritionally valuable compounds.

BACKGROUND: Softening is one of the main features that determine fruit quality during strawberry (Fragaria x ananassa, Duch.) ripening and storage. Being closely related to textural changes, the molecular and biochemical bases underlying strawberry cell‐wall metabolism is a matter of interest. Here we investigated the abundance of transcripts encoding putative strawberry endo‐xylanases in plant tissues, during fruit ripening and under postharvest and hormonal treatments. Total xylanase activity and expression of related genes in strawberry varieties with contrasting firmness were analyzed.RESULTS: FaXynA and FaXynC mRNA abundance was significantly higher than FaXynB in each plant tissue studied. Higher total xylanase activity was detected at the end of the ripening of the softer cultivar (‘Toyonoka’) in comparison with the firmer one (‘Camarosa’), correlating with the abundance of FaXynA and FaXynC transcripts. Postharvest 1‐methylcyclopropene treatment up‐regulated FaXynA and FaXynC expressions. FaXynC mRNA abundance decreased with heat treatment but the opposite was observed for FaXynA. Calcium chloride treatment down‐regulated FaXynA and FaXynC expression. Both genes responded differently to plant growth regulators' exposure. FaXynC expression was down‐regulated by auxins and gibberellins treatment and up‐regulated by abscisic acid. FaXynA was up‐regulated by auxins, while no changes in mRNA levels were evident by abscisic acid and gibberellins treatment. Ethephon exposure did not change FaXynA and FaXynC expressions.CONCLUSION: New knowledge about the presence of xylanases in ripening strawberry fruit and their response to postharvest and hormonal treatments is provided. Our findings suggest a role for endo‐xylanases in hemicelluloses depolymerization and possibly in strawberry fruit softening. © 2020 Society of Chemical Industry