Effects of Post-harvest Pre-cooling Processes and Cyclical Heat Treatment on the Physico-chemical Properties of “ Red Haven Peaches” and “Shahmiveh Pears” During Cold Storage

Ahmad Kalbasi-Ashtari

Abstract


The effects of different post-harvest hydrocooling solutions along with conventional cold
storage and cyclical heat treatment on the physico-chemical properties and sensory characteristics
of Persian “Red Haven” peaches and “Shahmiveh” pears were studied. Peaches and pears were
harvested at 24oC and at 26oC respectively and immediately pre-cooled with: 20oC ambient air,
14oC raw water, plain ice water, ice water + 2% (W/W) CaCl2, and ice water + 2% (W/W) CaCl2 +
100ppm chlorine respectively for a holding time of 24h, 45, 30, 30 and 30 min until their final
temperatures reached to 20oC, 15oC, 4oC, 4oC and 4oC. Pre-cooled fruits were transferred to cold
storage at 2oC and 85%RH respectively for 4 and 10 weeks. All the peaches were brought out of the
cold storage once a week for about 10 hours and held at 20oC ambient temperature to prevent
possible chilling injuries. Periodical measurements of physico-chemical parameters of fruits during
storage and their sensory evaluation after storage showed that in most of the cases peaches and
pears pre-cooled with different ice water solutions had significantly higher firmness, pectin content,
organoleptic scores and lower weight loss than air-cooled samples. Addition of CaCl2 to ice water
along with cyclical heat treatment during storage increased the firmness (up to 50%) and lowered
the pectin hydrolysis and weight loss of peaches up to respectively 25% and 50%. Similarly,
addition of CaCl2 to ice water increased the firmness (up to 60%) and lowered the pectin hydrolysis
and weight loss of pears up to respectively 30% and 40%. Sensory analysis also showed that
peaches and pears precooled with ice water containing CaCl2 had significantly higher firmness and
more attractive appearance, color and flavor than air cooled samples.

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