Comparison of practical methods for postharvest preservation of loquat fruit
Introduction
Ninghaibai is a white-fleshed loquat cultivar. Due to its excellent sensory quality, Ninghaibai cultivation at present covers more than 2.8 million ha in China. However, compared with some of the yellow-fleshed loquats, Ninghaibai has relatively poor keeping qualities and it is also rather susceptible to postharvest pathogenic microorganisms.
There are a number of methods for extending the postharvest life of fruit. Protective packaging has shown promise with various packaging being combined with low storage temperatures and high humidities both to extend shelf life and also to maintain sensory quality (Jacobsson et al., 2004, Esturk et al., 2012, Pareek et al., 2014, Candir et al., 2011, Ding et al., 2002). For example, pears packed in corrugated cardboard boxes with high-density polyethylene or un-perforated polypropylene liners can give good results in terms both of sensory quality and also of shelf-life extension (Kaur et al., 2013, Kaur et al., 2014, Nath et al., 2012).
An alternative is the use of edible coatings, and these have received greater attention in recent years due to their environmental friendliness, effectiveness and enhanced consumer acceptance (Han 2014). Examples of coating materials available are: carnauba and mineral oil coatings on tomatoes (storage for 28 d at 10 °C; Dávila-Aviña et al., 2014), composite coatings of 2% sodium alginate, 0.2% olive oil and 1% ascorbic acid on Chinese dates (Ziziphus mauritiana) (10 d at 25 °C; Rao et al., 2016). In addition, shrimp shell chitosan and N,O-carboxymethyl chitosan can extend the shelf life of tomatoes (Benhabiles et al., 2013a). A double-layer coating with 600 nm droplet size +1.0% conventional chitosan has a good effect on keeping quality of dragon fruit for up to 28 d at 10 °C (Ali et al., 2014).
A number methods have been evaluated for extending the shelf-life of loquats. Controlled atmospheres with 10% O2 +1% CO2 was effective in maintaining loquat quality for more than 50 d at 1 °C (Ding et al., 2006). The fruit quality of the loquat Mogi could be maintained for up to 30 d at the low temperature of 1 °C or 5 °C (Ding et al., 1998). Cai et al. (2006a) found that low-temperature conditioning alleviates chilling injury in loquat and extends storage time for up to 60 d. The loquat Luoyangqing treated with 5 μL L−1 1-methylcyclopropene showed excellent postharvest quality of firmness and reduced browning (Cai et al., 2006b). Shao et al. (2013) found that after short-term, hot-air treatment (45 °C for 3 h) loquats showed reduced chilling injury after stored at 5 °C for 35 d. Loquats treated with 1 mmol L−1 aqueous acetylsalicylic acid prevented chilling injury and decreased lignification (Cai et al., 2006c). Ding et al. (Ding et al., 2002) found that a combination of controlled atmosphere (approximately 4 kPa O2 and 5 kPa CO2) and 20 μm thick PE film at 5 °C allowed loquats to be stored for 60 d with a higher quality and minimal risk of disorder development. Coating with 0.75% chitosan was an effective method of maintaining loquat quality attributes for 28 d at 7 °C (Ghasemnezhad et al., 2011).
In this study, we compare six convenient methods for postharvest preservation of the white-fleshed loquat cultivar Ninghaibai. These methods have not previously been reported and include four different packaging materials and one film coating agent at two different thicknesses.
Section snippets
Fruit material and treatment
Mature fruit of loquat Eriobotrya japonica Lindl. cv. Ninghaibai were harvested from ten-year-old trees in Ninghai, Zhejiang, China. A total of 6300 fruit were selected for the experiment. These were of uniform size and color, and on visual inspection were free of disease and mechanical damage.
The fruits were randomly divided into seven treatments with three repetitions per treatment and 300 fruits per repetition. The control and the six treatments were: (T1) fruit were wrapped in sterile
Weight loss
Fruit weight decreased with duration of storage in all treatments and in the controls. Fruit treated with each of the packing methods and with the KGM coatings all showed significantly reduced weight loss compared with the controls (P < 0.05), exceptions were T5 at 7 d and T3 at 21 d. The least weight loss occurred with wrapping T1 with a weight loss rate of just 1.9% after 42 d storage at 4 °C. The KGM coatings T5 and T6 also showed good reductions of weight loss (Fig. 2A).
TSS and TA content
Treatments T5
Discussion
Packaging materials are well known to be very important for fruit storage. High moisture levels are maintained inside, and these help to slow fruit weight loss (Ding et al., 2002, Ding et al., 2006, Amorós et al., 2008). We chose four different materials to package our Ninghaibai loquat fruit. Sterile non-woven gauze (T1) and expanded polyethylene (T2) are both recyclable and environmentally friendly. Our results show that both these products prolong storage time for Ninghaibai loquats, helping
Acknowledgments
This work was supported by the National Natural Science Foundation of China (No. 31570679, 31170638), Ningbo Significant Science and Technology Project (No. 2013C11022).
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