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Storing Apricots in a Modified Atmosphere – Bio Fresh

The report was submitted to the Fruit Association by:

Susan Lurie and Assia Wexler, Storage Division, Volcanic Institute

Yitzchak Kosto, Training and Professional Services, Ministry of Agriculture

 

Introduction

One main strain of apricot is grown in Israel, the “Ra’anana”.  Large quantities of Ra’anana ripen throughout the country within the same two to three week period during the month of June.  In order to prevent a drop in prices and the increase the marketing period, the fruit is stored at 0°C.  However, the optimal storage period, while maintaining the quality of the fruit, is up to three weeks, depending on the physiological ripening of the fruit when it is picked. 

Storing the fruit beyond three weeks is likely to cause problems of internal browning of the fruit’s pulp.  Research studies conducted in the past have shown when the fruit is stored under controlled conditions the period of storage can be extended to five weeks without damage to the peel, as long as CO2 levels remain between 10%-15%.

An experiment was conducted at the “Rafkor” packing house in which the fruit was individually was sealed in baskets lined with Xtend liners, manufactured by Setpac, geared towards creating a control environment within the liners.   The significant factor of the experiment was the high concentration of CO2 during the prolonged period of storage.  The following year, a decision was made to seal complete crates (a total of 21) within a huge layer of liner in order to create a modified atmosphere within the crates.

 

Methodology

The fruit was picked at a commercial harvest on June 28, 2001 and was cooled overnight by forced air systems at the packing house.  Sixteen crates were selected for the experiment.  The fruit was bright yellow with a green border.  The crates were lined with different types of liners and 18 cartons of fruit (8 kg. of fruit packed into four plastic trays) were placed into each crate.  The upper sections of the crate were covered and bound. Three cartons in each crate were left outside of the covering liner as a control group.  The treatment groups were as follows:

Bio fresh liners made by Grofit Plastics Bio Fresh – four crates

Polyethylene liners (PE), 70 microns thick – three crates

Polyethylene liners (PE), 150 microns thick – three crates

One crate in which the fruit was placed on Xtend liners made by Setpac – each carton was placed separately (as done during the experiment conducted the previous year)

Five additional crates covered with polyethylene sleeves, 40 microns thick, used to cover crates of pears; one crate was covered separately and the remaining four crates were divided into two sets and covered in pairs.

The room temperature in which the crates were stored was 6.5°C and the temperature of the fruit was 2.5°C.  The crates were sent to storage at a temperature of 0°C and were left there for 34 days, until July 1, 2001.  The air from each of the liners was analyzed on June 6th, June 19th and July 1st, immediately prior to the opening of the crates.  The liners that indicated a level of oxygen below 2% were perforated with a syringe.

On July 1, 2010, three cartons of apricots were taken from each crate (two cartons that had been in a modified atmosphere and one carton from the control group).

The fruit was examined upon removal, once again after two days and finally, after an additional two days.  The latter two examinations were conducted after the fruit had been stored at shelf temperature (20°C) during the four days in mention.  The properties examined included: 

  1. Internal and external damage – the degree of internal browning (the primary problem) was defined as mild, medium or severe.
  2. Decay.
  3. The color of the peel on the “a” scale of the Minolta chronometer and based on the visual ranking of greenish yellow, yellow or bright yellow.
  4. Firmness – using a Penifil penetrometer with a head 8mm thick on peeled fruit samples.
  5. Sugar level – Soluble Assimilated Quantity (SSC) in the juice of ten apricots, using an Atago refractometer.
  6. Acidity (TA) – the level of acid in the juice as measured by an automatic Metrohm titration device.

Two repetitive tests were conducted on each carton on each of the testing dates.

 

The Results

The treatments and the gas levels found in the crates are presented in Table 1.

The Grofit Plastics Bio Fresh liners maintained CO2 levels of less than 20% and an oxygen level higher than 2% - the target range for CO2 and oxygen levels.  Similarly, CO2 levels between 10% - 15% were found in the individual cartons lined with Xtend liners.  The oxygen levels were higher in the Xtend liners, in comparison to the Grofit Plastics Bio Fresh liners, as the Xtend liners are micro perforated (with tiny holes).  The desired modified atmosphere was not achieved with the PE liners.

CO2 levels exceeding 20% were found in the liners that were 70 microns thick and the addition of micro perforation did not reduce these levels, rather merely prevented their increase.  It was not possible to seal the liners that were 150 microns thick.  This explains the differences between crates from the same treatment group.  However, these liners also enabled the production of excess levels of CO2.

Upon removal from refrigeration, all of the fruit looked healthy except for the fruit from the crate in which the CO2 level exceeded 20%.  Brown bruise marks were visible on the skin of the fruit, a clear sign of CO2 damage.  In all of the treatment groups, the fruit’s skin was bright yellow, firm and showed little decay (Table 2).

 

In most of the treatment groups, the firmness and the acidity levels of the fruit were higher in the fruit stored in a modified atmosphere, in comparison to the fruit in the control group that had been exposed to regular air.  Skin color and SCC levels were similar in both the control groups and the modified atmosphere group.

The fruit from the crates with the Xtend liners maintained higher levels of firmness and acidity than the fruit in the other treatment groups.  A small amount of internal browning was noted in the fruit when it was removed from refrigeration, except for the fruit in the crates lined with PE liners, 150 microns thick, which showed only slight browning of the pulp (data not presented).

The quality of the fruit after being stored at 20ºC for two days and four days is indicated in Table 3 and in Illustration 3.

In all of the treatment groups with a modified atmosphere, the fruit maintained its firmness, had a bright skin color and showed less or delayed internal browning, in addition to less amounts of gel on the pulp.  There was little decay among the fruit stored in the crates lined with Xtend and Grofit Plastic Bio Fresh liners.  However, in the crates lined with PE liners, damage was caused by the high levels of CO2.

Covering the crates with plastic used for pears did not produce a modified atmosphere and therefore, did not lead to the positive effects obtained from the other coverings. After two days of shelf life, high levels of internal browning were found in the fruit that had been stored in these crates.  This was similar to the finding noted for the control group.

Two crates, lined with Xtend and Grofit Plastics Bio Fresh liners, maintained the quality of their contents throughout the entire 34 days of storage at 0ºC, and for an additional two days of shelf storage at 20ºC.  In these treatment groups, the levels of CO2 ranged between 10% - 20%.  The fruit in these treatments groups maintained adequate firmness, even after four days of shelf life.  After two days of shelf storage at 20ºC, the level of decay, the browning of pulp and the development of gel were low, if at all.  In contrast, after four days of shelf storage, internal browning was noted as being high, even though it was lower than the level of the control group.

It can be concluded that storage under modified atmosphere conditions leads to higher quality fruit, even after a period of five weeks, but the shelf life is shorter.

We would like to thank the “Rafkor” Packing House for their assistance and contribution in conducting this experiment.

 

Table 1: Treatments and composition of gases bags of apricots stored in a modified atmosphere

Treatment

 

CO2 levels

O2levels

 

Date

17.6

19.6

1.7

17.6

19.6

1.7

 

Repetition

 

 

 

 

 

 

Grofit Plastics Bio Fresh

1

11.3

15.8

19.7

6.1

 2.6

 2.4

 

2

13.2

15.4

16.5

 2.5

3.6

3.6

 

3

12.4

12.8

16.9

4.3

7.5

5.1

 

4

13.4

15.2

18.4

4.1

4.8

2.1

PE 70 microns

1*

11.1

22.8

23.1

9.5

2.7

2.1

 

2*

14.0

22.7

28.2

5.3

2.1

1.0

 

3*

15.3

18.9

21.7

2.6

 2.8

2.3

PE 150 microns

1

7.2

7.54

10.3

13.3

13.7

12.9

 

2

7.1

9.9

24.5

13.5

11.5

3.9

 

3*

14.9

21.1

22.9

5.1

2.1

3.2

Xtend

1

15.3

13.9

15.0

3.1

9.4

9.5

 

2

14.1

14.0

12.7

3.8

10.3

7.2

 

3

12.9

13.8

12.2

7.2

9.2

9.8

 

4

14.8

16.2

15.8

4.4

9.8

12.0

 

5

10.9

12.4

15.0

8.4

9.8

11.0

 

6

13.3

13.7

13.2

6.4

8.1

9.3

Pear PE

1

 

 

0.4

 

 

20.6

 

2

 

 

0.6

 

 

20.6

 

3

 

 

0.5

 

 

20.5

*The bags were perforated with a needle following the June 19th testing. Between 20 and 30 holes were made.

Table 2: Apricot quality after 34 days of storage at 0 ºC in regular air or in a modified atmosphere

Treatment

Firmness

SCC (%)

Acidity (%)

“a” color

CO2 damage

 

Air

MAP

Air

MAP

Air

MAP

Air

MAP

 

Grofit Plastics Bio Fresh

4.1

5.5

14.2

14.3

1.0

1.2

7.0

5.5

 

 

6.8

6.5

13.1

14.6

1.1

1.1

2.9

7.9

 

 

6.7

4.5

13.7

12.6

1.0

1.4

3.3

2.1-

 

 

6.9

8.5

14.0

15.5

1.0

1.3

1.4

3.2

 

PE 70 microns

7.2

8.5

13.3

13.5

0.95

1.3

1.9-

3.2

+

 

7.7

8.4

13.7

13.2

1.1

1.3

2.8

3.2

+

 

6.9

5.5

15.2

15.6

0.9

1.4

2.7

5.6

 

PE 150 microns

6.9

6.3

15.2

14.2

0.9

1.4

2.7

2.7

+

 

6.9

6.5

16.3

13.4

1.2

1.2

1.8

1.3

+

 

5.8

7.8

15.0

13.4

1.0

1.7

1.0

0.6

 

Xtend

 

8.6

 

12.0

 

1.3

 

1.6

 

 

 

8.7

 

12.9

 

1.4

 

2.6

 

 

 

8.3

 

15.0

 

1.4

 

3.9-

 

 

 

9.4

 

11.8

 

1.4

 

2.6

 

 

 

7.9

 

13.9

 

1.4

 

3.5

 

 

 

8.1

 

13.4

 

1.4

 

3.5-

 

Pear PE

6.4

 

13.5

 

0.8

 

2.4

 

 

 

6.5

 

12.3

 

1.2

 

0.8-

 

 

 

6.2

 

12.6

 

1.0

 

2.6

 

 

 

Table 3:  Apricot quality after two days and four days of storage at 20ºC

 

Treatment

Grofit  Plastics

Control Group

PE 70

Control Group

PE 150

Control Group

Xtend

PE for Pears

Firmness

2 days

5.3

1.2

5.7

4.6

6.3

5

8

5.1

Core

4 days

5

3.8

4.7

3.6

6.5

4.7

7.9

4.4

Soft Fruit

2 days

16

29

19

--

33

39

0

25

%

4 days

30

92

33

8.1

49

75

4

77

Yellow Skin

2 days

27

12

23

--

16

--

28

--

 

 

 

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