The role of heat treatments and pectin compounds in the occurrence of chilling injury in nectarine fruit (Prunus persica var. nectarina Ait.) during storage

Abstract

Istraživano je djelovanje toplinskih tretmana na sadržaj frakcija pektina (pektini topljivi u vodi, pektini topljivi u amonijevom oksalatu i pektini topljivi u natrijevoj lužini), pojavu ozljeda od niskih temperatura i senzorna svojstva nektarine sorata 'Diamond Ray' i 'Venus' čuvanih dva i četiri tjedna na 0°C u normalnoj atmosferi i pet dana života na polici. Primijenjeni toplinski tretmani bili su potapanje u toplu vodu temperature 48 °C u trajanju šest i 12 minuta (HWD 48 °C 6' i HWD 48 °C 12'), potapanje u toplu vodu temperature 52 °C u trajanju od dvije minute (HWD 52 °C 2') i tretman vrućim zrakom temperature 45 °C u trajanju od 60 minuta uz podizanje temperature za 24°C svakih 60 minuta, sve dok temperatura mezokarpa kraj koštice ne dostigne 45 °C (HAT 45 °C/24). Kod sorte 'Diamond Ray' tretman vrućim zrakom nije smanjio ozljede od niske temperature, ali ih nije ni povećao, dok su vodeni tretmani (HWD 48 °C 6', HWD 48 °C 12' i HWD 52 °C 2') povećali udio plodova s ozljedama od niskih temperatura. Sorta 'Venus' nije pokazala simptome ozljeda od niskih temperatura. Utjecaj je toplinskih tretmana na udjele frakcija pektina različit, ovisno o sorti i duljini čuvanja plodova. Pektini topljivi u amonijevom oksalatu imaju važnu ulogu kod ozljeda od niskih temperatura. Plodovi s većim udjelom pektina topljivih u amonijevom oksalatu imali su niži udio plodova s ozljedama od niskih temperatura. Utvrđena je povezanost omjera pektina topljivih u vodi i pektina topljivih u amonijevom oksalatu intenzitetom ozljeda od niskih temperatura, što ukazuje da bi taj omjer mogao bi biti dobar pokazatelj ozljeda od niskih temperatura. Toplinski tretmani ne narušavaju kakvoću ploda nektarine, ali utječu na senzorna svojstva plodova nakon čuvanja dva i četiri tjedna na 0 °C i pet dana života na polici.The effect of heat treatment on the ratio of the pectin fractions (water soluble pectin, ammonium oxalate soluble pectin and sodium hydroxide soluble pectin), the occurrence of chilling injury and sensory properties nectarine cultivars 'Diamond Ray' and 'Venus' stored 2 and 4 weeks at 0 °C in normal atmosphere and 5 days of shelf life was studied. Heat treatments that were applied were hot water dip treatment at temperature 48 ° C for 6 and 12 minutes (HWD 48 °C 6'and HWD 48 °C 12', respectively), at temperature 52 °C for 2 minutes (HWD 52 °C 2 ') and treatment with hot air at temperature of 45 °C for 60 minutes, followed by raising the temperature to 24° C every 60 minutes until the temperature of the mesocarp at stones reaches 45 °C (HAT 45°C/24). Treatment of hot air did not reduce development of chilling injury of nectarine 'Diamond Ray', but also did not increase, while water treatments (HWD 48 °C 6', HWD 48 °C 12'and HWD 52 °C 2') showed an increase in chilling injury development. Nectarine 'Venus' had no symptoms of chilling injuries. Heat treatment had different effect on the ratio of the different fractions of pectin depending on cultivar and storage. Ammonium oxalate soluble pectin fraction play an important role in chilling injury development. Fruit with higher ratio of ammonium oxalate soluble pectin had lower ratio of chilling injured fruit. It was found good relationship between the ratio of water-soluble pectin and ammonium oxalate soluble pectin with intensity of chilling injuries which shows that this ratio could be a good indicator of chilling injury. Heat treatments do not impair the quality of the nectarine fruit, but affects the sensory properties of fruit after 2 and 4weeks of storage at 0 ° C and 5 days of life on the shelf