Karl Foord, UMN Extension Educator
The fresh peach season is upon us, and there are few things as bad as the anticipation of a delicious peach only to discover that the flesh is mealy and mostly inedible. I have been burned enough by mealy peaches to be wary of buying them in grocery stores. It is extremely difficult to look at a peach and determine whether the flesh is mealy. This makes peaches a risky purchase because you never know whether you will be delighted or disappointed. This article addresses two topics; 1) how you can improve the chances of not getting a mealy peach, and 2) how does peach flesh become mealy?
Carlos H. Crisosto, Department of Plant Sciences, UC Davis
Top: Flesh browning. Bottom: Healthy peach.
The best way I know to reduce the chance of buying a mealy peach is to reduce the time from farm to your house as well as the number of transfer points that the peach travels through in getting to you (Figure 1). One way to do this is to purchase fruit in bulk from a local Pick-Your-Own (PYO) farm that will deliver fruit direct from a peach grower in Michigan. The farmer contacts these entities when the peaches are ready. A truck is procured and the peaches travel to a central PYO and from there to your PYO where you are called to pick up the peaches. The peaches can get to you in a matter of days.
Explaining how a peach becomes mealy requires understanding the fruit distribution process and the physiology of the peach. Peach flesh becomes mealy if a physiologically immature peach is placed in cold storage or a physiologically mature peach is stored at suboptimal temperatures. To avoid the first problem, peaches are harvested and then "conditioned" at 68°F for 24 hours to ensure that all are physiologically mature. To avoid the second problem, following conditioning the peaches should be chilled to between 32° and 37°F and kept in this range throughout the processes taking the peach from farm to retail store. At the retail store the peaches can be brought back to 68°F where they can ripen in a 4 to 6 day range at which point they will be ready-to-eat.
Peaches stored in the 38° to 51°F temperature range develop mealy brown flesh and ripen inconsistently. Peaches stored in the 31° to 34°F temperature range with 90% relative humidity can maintain quality for two weeks or more. If peaches are exposed to temperatures at or below 30°F, their tissues will be damaged by freezing.
If the most likely cause of mealy peaches is storage in the 38° to 51°F temperature range and we are still buying mealy peaches, then somewhere in the shipping and distribution process the peaches are experiencing this temperature range. This could be because it is difficult to maintain this cold chain or because of the great variety of fruits and vegetable being shipped, compromises must be made during transport. Not all fruits and vegetables have the same optimum storage temperature. Apples and peaches do well at 32°F, whereas grapefruit like 50° to 60°F, lemons like 45° to 48°F and the temperature optimum for oranges depends on where they come from. California oranges have a different temperature optimum (45-48°F) than Florida (32-34°F) which has a different temperature optimum than Arizona and Texas (32-48°F).
As a scientist it would be interesting to know where the system breaks down, however as a consumer I just want to find the easiest way to get a great tasting peach.
Ask your Pick-Your-Own farmer if they purchase Michigan Fruit for sale through their business.
L. Kitinoja and A. A. Kader, Postharvest Horticulture Series No. 8E, Postharvest Technology Research and Information Center, University of California, Davis 2002.