نوع مقاله : مقاله پژوهشی
نویسندگان
1 استادیار پژوهشی، بخش تحقیقات فنی و مهندسی کشاورزی، مرکز تحقیقات و آموزش کشاورزی و منابع طبیعی استان خوزستان، سازمان تحقیقات، آموزش
2 مربی پژوهش، بخش تحقیقات فنی و مهندسی کشاورزی، مرکز تحقیقات و آموزش کشاورزی و منابع طبیعی استان خوزستان، سازمان تحقیقات، آموزش
3 کارشناس محقق، بخش تحقیقات فنی و مهندسی کشاورزی، مرکز تحقیقات و آموزش کشاورزی و منابع طبیعی استان خوزستان، سازمان تحقیقات، آموزش
چکیده
کلیدواژه‌ها
موضوعات
عنوان مقاله [English]
نویسندگان [English]
Proper management of post-harvest systems is one of the most crucial steps in reducing agricultural losses and waste. This study was aimed to find the effect of forced air pre-cooling of dill using a window air conditioner on its shelf life. For this purpose, a metal frame with dimensions of 2×1×1 m was covered with a polyethylene foam sheet and a window air conditioner (after removing its thermostat) equipped with a controller was connected to one end of this chamber. In the next step, bunches of dill without packaging and the cardboard packaging with polyethylene liner were placed in three different conditions, including without pre-cooling and keeping at ambient temperature, with pre-cooling and keeping at ambient temperature, with pre-cooling and keeping under refrigeration. The results showed that during 4 days of storage, bunches of dill kept at ambient temperature had more total loss (50-60%) but after that, packaging caused severe loss (100%) due to moisture accumulation. If cold storage and packaging was ignored after pre-cooling, total loss would increase swiftly. For this reason pre-cooled dill with proper packaging and refrigeration showed the least amount of total loss (8.95±1.03%), physiological water loss (5.16±1.78%), pH (6.16±0.16), a*(-20.29±1.45) and the highest amount of moisture content (87.60±3.76), hardness (764±50 N), ascorbic acid (2.74±0.05 mg. g-1 of dill dry weight basis), total acceptance (4.1±0.65), L* (43.44±6.39), and b* (20.09±4.31).
کلیدواژه‌ها [English]
The effect of forced air pre-cooling on dill shelf life
EXTENDED ABSTRACT
The pre-cooling process is the first and most crucial step in temperature management. It is generally defined as the procedure of removing heat immediately after harvest and before storage or handling to decrease food loss and waste. Any delay in pre-cooling can negatively affect food security and safety, and is also considered a major economic problem for the supply chain of agricultural products. The effect of poor pre-cooling is only apparent when decay and water loss result in rejected loads during distribution, so this process is not taken seriously by farmers. A range of techniques are available to achieve the pre-cooling process for fresh produce but many of them are restricted for small scale producers because of their high cost. Many studies have been performed on the development of innovative small-scale equipment. Characteristics of crops, load volume, initial and target temperature and its cost should be considered well to select wisely. This study was aimed to find the effect of forced air pre-cooling of dill using a window air conditioner on its shelf life.
A metal frame with dimensions of 2×1×1 m was covered with a polyethylene foam sheet (as a cheap insulator) with a thickness of 1 cm. A window at the end of this chamber (to install the window air conditioner) and a door in one side for entering and exiting the product were considered. The thermostat of the window air conditioner was moved to the outside of the pre-cooling chamber. A controller equipped with 8 sensors was connected to monitor and control the temperature of this chamber. 10 Kg plastic boxes of dill were placed inside the chamber in the form of 3×2×2 boxes (length, width and height) with a distance of 10 cm. After turning on, the temperatures were recorded over time, and 1/2 and 7/8 cool time were determined. In the next step, bunches of dill without packaging and in the cardboard packaging with polyethylene liner were placed in three different conditions: without pre-cooling and keeping at ambient temperature, with pre-cooling and keeping at ambient temperature, with pre-cooling and keeping under refrigeration. Total loss (%), physiological water loss (%), hardness (N), pH, CIELAB color, ascorbic acid (mg/g) and total acceptance were measured over time. A Factorial experiment with a basic RCBD design was used for data analysis and means comparison was done by Duncan's multiple range test in α=0.05.
The constructed pre-cooler was successfully cool down field temperature of dill bunches. 37 min and 92 min were determined as 1/2 and 7/8 cool time, respectively using cooling curve while the relative humidity was 81.95±1.66% inside this chamber. The results showed that different treatments and time had significant interaction on Total loss, physiological water loss, hardness, pH, CIELAB color (L*, a*, b*), Ascorbic acid and total acceptance. The total loss es of dill stored at ambient temperature and without packaging (with or without pre-cooling treatment) at day=2, 4 were significantly higher than others due to higher physiological water loss while after 6 days of storage, total losses of packed dill stored at ambient temperature were reached to 100% due to bacterial soft rot. After 6 days of storage pre-cooled dill with packaging and refrigeration showed the least amount of total loss (8.95±1.03%), physiological water loss (5.16±1.78%), pH (6.16±0.16), a*(-20.29±1.45) and the highest amount of moisture content (87.60±3.76), hardness (764±50 N), ascorbic acid (2.74±0.05 mg. g-1 of dill dry weight basis), total acceptance (4.1±0.65), L* (43.44±6.39) and b* (20.09±4.31).
According to the results obtained here, pre-cooling can alleviate negative effects of high temperatures immediately after harvest. Pre-cooling followed by packaging and refrigeration could effectively limit total loss to 20% after 10 days. If pre-cooling or packaging is not followed by refrigeration, progressive and significant losses can occurr. Further research is required to compare the effect of different packaging materials and dimensions on dill shelf life.
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