Pomegranate Husk Scald Browning during Storage: A Review on Factors Involved, Their Modes of Action, and Its Association to Postharvest Treatments

Abstract

The pomegranate (Punica granatum L.), which contains high levels of health-promoting compounds, has received much attention in recent decades. Fruit storage potential ranges from 3 to 4 months in air and from 4 to 6 months in Controlled Atmospheres (CA) with 3–5% oxygen and 10–15% carbon dioxide. Storage life is limited by decay, chilling injury, weight loss (WL), and husk scald. In particular, husk scald (HS) limits pomegranate long-term storage at favorable temperatures. HS appears as skin browning which expands from stem end towards the blossom end during handling or long-term storage (10–12 weeks) at 6–10 °C. Even though HS symptoms are limited to external appearance, it may still significantly reduce pomegranate fruit marketability. A number of postharvest treatments have been proposed to prevent husk scald, including atmospheric modifications, intermittent warming, coatings, and exposure to 1-MCP. Long-term storage may induce phenolic compounds accumulation, affect organelles membranes, and activate browning enzymes such as polyphenol oxidases (PPO) and peroxidases (POD). Due to oxidation of tannins and phenolics, scalding becomes visible. There is no complete understanding of the etiology and biochemistry of HS. This review discusses the hypothesized mechanism of HS based on recent research, its association to postharvest treatments, and their possible targets.

Prevention of Chilling Injury in Pomegranates Revisited: Pre- and Post-Harvest Factors, Mode of Actions, and Technologies Involved

“… Integral model linking pre-harvest and harvest factors and its effects on chilling injury (CI) development during postharvest storage of pomegranate fruit. This integrative approach based on studies reported in the literature (see Section 3.1 and Section 3.2 ) can be used as a reference for identifying and introducing future studies on pre-harvest and harvest factors and also dissect their effects on different pomegranate fruit quality attributes and physiological disorders besides CI (e.g., husk scald effects [ 17 ]. Accordingly, chemical treatments (e.g., MeJa, ASA, salicylic acid, arginine), fruit variety, fruit maturity, shade, and irrigation will affect quality attributes (e.g., soluble solids, aril color, antioxidant enzymes, polyphenols) and reduce or favor chilling injury symptoms.…”

“…Proposed hypothetical model is based on references from Section 3.3 . Proposed model could be the basis of a hurdle strategy combining different technologies to attenuate CI in a similar fashion as previously described for husk scald disorder in pomegranate fruit [ 17 ].…”

“…The internal symptoms manifest as brown discoloration of the white segments between the arils and red color reduction or browning of arils as shown in Figure 2 [ 14 , 15 , 16 ]. Usually, pomegranates in short-term storage at <5 °C show CI symptoms starting from 6–8 weeks [ 17 , 18 ].…”

“…CI is different than husk scald development in pomegranate fruit that usually takes place at temperatures >6–10 °C and appears during long-term storage after 10–12 weeks, and is characterized by skin discoloration due to water loss and mediated by ABA signaling [ 17 , 18 ]. A similar mode of action of browning takes place in husk scald skin browning involving membrane damage, PPO, and oxidation of polyphenols [ 18 ].…”

Effects of 1–MCP Treatment on Postharvest Fruit of Five Pomegranate Varieties during Low-Temperature Storage

“…Although browning increases under 5 • C, storage at low temperatures is necessary [6]. Symptoms of peel browning include pitting, husk scald, some softening, a higher sensitivity to decay, internal seed discoloration, and browning of chilling injury in postharvest pomegranate fruit during low-temperature storage [29,33,35]. We observed peel browning in the three soft-seed pomegranate fruit ('Mollar', 'Malisi', and 'Tunisian soft seed') from 30-45 d and in the two semi-soft-seed fruit ('Moyuruanzi' and 'Dongyan') from 60 d after the low-temperature storage.…”