Method for shipment and ripening of peaches, nectarines & plums

The invention herein pertains to a process for improvement of stored fresh market fruits such as peaches, plums and nectarines by retarding mealiness, dryness and internal breakdown. Peaches in particular are routinely stored at 0.degree. C. to prevent softening. Unfortunately, "chilling injury" occurs in peaches, plums and nectarines stored by this conventional technique which can result in insurance claims, litigation and general consumer dissatisfaction. The invention comprises five steps for the transshipment thereof that results in enhanced fruit quality. This process is particularly suitable for imported fruits from overseas where transshipment by boat is required. The process can also be used to improve the quality of domestic fruits held for late-season "market window" sales.

FIELD OF THE INVENTION 
This invention pertains to a process for the combined harvest, shipping, 
handling, ripening and distribution of whole peaches, plums and nectarines 
for enhancement of fruit quality thereof. 
BACKGROUND OF THE INVENTION 
Although peaches are grown in temperate climates, they are 
"chill-sensitive" like tropical fruits. This "chilling injury" results in 
mealiness, browning and internal breakdown after lengthy storage around 
0.degree. C., although recommended by all industry guidelines, for 
example, see the i) U.S. Department of Agriculture marketing bulletin 
No.64 entitled "How Fresh Peaches are Marketed," August 1978 and ii)the 
School Food Journal's June/July 1987 edition entitled "Tree Fruit: Ancient 
Food Adapts to the 80's". Previous attempts to store peaches in 
"controlled atmosphere" have also been unsuccessful. This "chilling 
injury" is a consequence of low temperature controlled atmosphere storage 
conditions and long term air storage. In particular, the degradation of 
fruit quality is induced by long exposure at storage temperatures of less 
than 8.degree. C. 
In view of this problem, the invention herein provides a unique combination 
of steps for harvesting and post harvest handling of peaches, plums and 
nectarines that will minimize "chilling injury" and also prolong the shelf 
life of these fruits. 
SUMMARY OF THE INVENTION 
The present invention pertains to a process for improvement of stored fresh 
market peaches and nectarines by retarding mealiness, dryness and internal 
breakdown. Peaches are routinely stored at 0.degree. C. to prevent 
softening. Unfortunately, "chilling injury" occurs in peaches, plums and 
nectarines stored by this conventional technique can result in unwanted 
insurance claims, litigation and consumer dissatisfaction. The invention 
process herein consists of five sequential steps for enhancing quality of 
these fruits. The process is particularly suitable for imported fruit from 
overseas where marine transport is required. The invention herein will 
improve the quality of domestic fruits produced in the U.S. held for 
late-season "market window" sales. 
Accordingly, an object of the present invention is to provide an integrated 
process of harvesting, shipping, handling, and distribution of peaches, 
nectarines and plums in particular as well as other fruits that can use 
this method. Thus, the invention provides at a supermarket distribution 
level, fruits having: i) more flavor; ii) less acidity; iii) absence of 
mealiness and internal browning; and iv) last longer without molding. 
Still further advantages will become apparent from considering the ensuing 
detailed description.

DETAILED DESCRIPTION 
The following consecutive five steps describes the process for shipment of 
peaches, nectarines and plums in particular: 
Stage 1: Maturity: The fruit should be harvested early-mature. A 
Minolta.RTM. colorimeter "a" value of -8 or greener is required. This 
ensures that low-ethylene evolving fruit results which has a long storage 
life. This is a critical stage that must be followed. This overall process 
will not be effective with "late-mature" or "tree-ripe" fruit. 
Stage 2: Preshipment Period. Holding the fruit from stage 1 at 0.degree. C. 
is required. This should be for two weeks or less. The industry well known 
standard chlorination dip is may also be required during this period to 
inhibit mold growth, e.g. using standard 100 ppm sodium hypochlorite 
solution with a pH of 6.0. 
Stage 3: Shipment. Shipment at non-chilling temperature of 10.degree. C. in 
shipboard cargo containers maintained at 3% oxygen with a tolerance of 
.+-.1%, and 10% carbon dioxide with a tolerance of .+-.5% (controlled 
atmosphere storage). Appropriate devices that can accomplish this task 
include concepts developed by Anderson's U.S. Pat. No. 4,842,875 entitled 
"Controlled Atmosphere Package" which is hereby incorporated by 
reference. This teaching mentions the use of peaches as just one fruit 
used in the application of this invention; however, the actual O.sub.2 
/CO.sub.2 levels are not the same as required by the instant invention. 
The effect of low oxygen to reduce ethylene production is minimal at 8% 
oxygen on peaches. For low oxygen levels to be effective to bring about 
lower ethylene levels and thus ripening, the oxygen levels must be below 
5%. The instant invention reduces the oxygen levels around 3% to retard 
the ripening process. 
Additionally, U.S. Pat. No. 4,411,921 by Woodruff entitled "Method for 
Inhibiting Fungal Growth on Fresh Fruits and Vegetables" teaches of using 
O.sub.2 /CO.sub.2 /CO as a mixture for the shipment of fruits and 
vegetables in general, with peaches and nectarines as examples. However, 
this patent does not teach of: i) the critical time the peaches and 
nectarines must be picked as in the instant invention, ii) the lack of 
needing carbon monoxide (CO) in the shipment of fruit as by the instant 
invention, CO is a highly toxic agent and should be avoided in containers 
and iii) avoiding chilling temperatures to fruits during shipment. 
Other preferred container storage are ocean-going tractor trailer 
containers with atmospheric control capability to maintain these O.sub.2 
/CO.sub.2 levels. Additionally, an ethylene scrubber unit is a preferable 
add-on device to the container to maintain the ethylene content in the 
container not greater than 50 parts per billion to retard ripening of the 
fruit. This maintains the firmness of the fruit while in transit. 
Stage 4: Ethylene Treatment. Post-shipping exposure at the port-of-entry 
of-entry to ethylene gas in a "ripening room" to remove excess acidity in 
fruit and stimulate volatile aroma production. Exposure to a concentration 
of ethylene greater than 10 parts per million for between 4 to 24 hours is 
required. This step is illustrated in Erb's U.S. Pat. No. 3,924,010 
entitled "Method for Ripening Fruit in Atmosphere of Ethylene and Carbon 
Dioxide" which is hereby incorporated by reference. This reference 
provides detail as to the apparatus and ethylene treatment technique of 
ripening fruit in general, but does not use the same quantities of 
ethylene as in the instant invention. 
Stage 5: Post-shipping period. Deliver from the port-of entry to the 
consumer within 2 weeks using normal temperatures 0.degree. C. (32.degree. 
F.) and ambient atmospheric conditions. This fruit can be handled normally 
by local freight and warehouse operations receiving treated fruit while 
avoiding "chilling injury" that can occur after 17 days at 0.degree. C. 
______________________________________ 
Test Results: 
LORING PEACHES STORAGE STUDY AT 10.degree. C. 
At harvest, the mean fruit weight was 161.2 grams. 
The Hunter "a" value measured with a 
Minolta .RTM. Colorimeter was -12.0. 
Storage Treatment 
10.degree. C. in 3% O.sub.2 
10.degree. C. in Air 
and 10% CO.sub.2 
Storage Ethylene Firmness Ethylene 
Firmness 
Days (.mu.l/kg-hr) 
(kg force) 
(.mu.l/kg-hr) 
(kg force) 
______________________________________ 
0 -- 7.0 -- 7.0 
4 0.32 -- 0.13 -- 
12 2.38 -- 0.36 -- 
16 10.68 0.67 0.32 1.10 
15 24.10 -- 0.52 
25 273.52 -- 1.12 -- 
32 395.93 -- 1.43 -- 
34 359.26 0.62 1.41 0.80 
43* 469.55 -- 3.42 -- 
50** 505.66 0.20 9.79 0.31 
______________________________________ 
*External mold (Penicillium spp.) present on air stored fruit. 
**External mold (Penicillium spp.) present on 3% oxygen, 10% carbon 
dioxide stored fruit. 
***Fruit quality measurements of ethylene produced by peaches are reporte 
in microliters (.mu.l) per kilogram hour (.mu.l/kghr). Fruit firmness (kg 
force) was measured by an Effegi penetrometer rifted with the appropriate 
tip for peaches. Fruit was removed from respirometer jars on the dates 
noted. They were then placed in air at 20.degree. C. for four days. After 
that fourday period firmness measurements were taken. 
Since both treatments were given at 10.degree. C. fruits were juicy; no 
mealiness was detected in the fruit. 
At about day 16, standard storage techniques of the peaches become overly 
ripe and senescent whereas using the instant five stage method of the 
invention delayed such occurrence until about day 50, thus a threefold 
increase in allowable storage time. 
Alternative ways of doing major stages 2, 3, and 4 above can vary the 
maturity of peaches, plums and nectarines. In particular, temperature 
ranges of stage 2 of this concept can be varied to prevent softening 
without risking "chilling injury" by holding the temperature at 8.degree. 
C. (47.degree. F.). As to stage 3 above, lower levels of oxygen and higher 
levels of carbon dioxide can be effective to avoid damage to the fruits 
shipped. Moreover, ethylene sampling of the fruit at the port of entry can 
be performed to determine whether stage 4 is required and estimate "shelf 
life" of the fruits at the port of entry. 
Although the description above contains many specificities, these should 
not be construed as limiting the scope of this invention as set forth in 
the appended claims, but as merely providing illustration of the presently 
preferred embodiment of this invention.