Effects of storage and processing on apple phytochemicals storage

Apple phytochemical content is not greatly affected by storage. Quercetin glycosides, phloridzin, and anthocyanin content of Jonagold, Golden Delicious, Red Delicious, Elstar, and Cox's Orange apples were not affected by 52 weeks of storage in controlled atmospheric conditions. Chlorogenic acid and total catechins decreased slightly in Jonagold apples. Total catechin concentration decreased slightly in Golden Delicious, but chlorogenic acid concentrations remained stable [72]. After 25 weeks of cold storage, there was no decrease in chlorogenic acid in any variety of apple, but catechin content decreased slightly in Golden Delicious, Elstar, and Cox's Orange apples. Both types of storage had no effect on antioxidant activity in any variety of apple examined. Another group looked specifically at the effects of storage on apple peel phenolics and found that storage at 0°C for 9 months had little effect on phenolic content [79]. Lattanzio et al. (2001) found that after 60 days of cold storage the concentration of total phenolics in the skin of Golden Delicious apples increased. After 100 days, the total phenolics in the skin began to decrease, but even after 200 days in storage, the total phenolics were similar to those at the time of harvest [80].


Processing of apples has been found to affect phytochemical content. Apple juice obtained from Jonagold apples by pulping and straight pressing had 10% of the antioxidant activity of fresh apples, while juice obtained after pulp enzyming had only 3% of antioxidant activity. After pulp enzyming, the juice contained 31% less phloridzin, 44% less chlorogenic acid, and 58% less catechin. Most of the compounds remained in the apple pomace [81]. Similarly, Guyot et al. (2003) found that 42% of total phenolics were extracted in the juice, leaving over half the total phenolics in the apple pomace. They found that hydroxycinnamic acids and dihydrochalcones showed the greatest extraction yields in the juice, 65% and 80 % respectively. Procyanidins had the lowest yield in the juice (32%) [82]. Apple phenolics, especially procyanidins, have been found to bind with cell wall material, which could lead to the decreased levels of polyphenols found in apple juices [83].

Apple pomace is a major waste product accumulated mainly during apple juice processing. Phloridzin, chlorogenic acid, epicatechin, and quercetin glucosides have all been isolated from apple pomace [84]. These phenolics isolated from apple pomace have been found to have high antioxidant activity suggesting that apple pomace may have dietary health benefits and commercial use [84]. Millions of pounds of waste apple peels are generated in the production of applesauce and canned apples in New York State each year. Since apple peels contain a majority of the antioxidants when compared to the flesh [85], apple peels have the potential to be a value-added ingredient in food products. Apple peels were blanched and then dried under a variety of conditions (oven dried at a range of temperatures between 40° and 80°, air dried, or freeze dried). The freeze-dried samples had the greatest total phenolic and flavonoid content, and the total phenolic and flavonoid was actually greater than in the fresh peels. The apple peel powder had strong antioxidant activity and also greatly inhibited cancer cell proliferation [85].



In numerous epidemiological studies, apples have been associated with a decreased risk of chronic diseases such as cardiovascular disease, cancer, and asthma. In vitro and animal studies have demonstrated that apples have high antioxidant activity, can inhibit cancer cell proliferation, decrease lipid oxidation, and lower cholesterol, potentially explaining their role in reducing risk of chronic disease. Apples contain a wide variety of phytochemicals, many of which have been found to have strong antioxidant activity and anticancer activity. The interaction of the many apple phytochemicals warrants more study as researchers attempt to further explain the mechanism behind the apple's ability to reduce risk of chronic disease. Recent research has shown that apples do contain bioavailable phytochemicals, although more work is needed to better understand the bioavailability of phytochemicals within the apple matrix as opposed to pure phytochemicals.Many factors affect the phytochemical profile of apples, and are important to consider as one attempts to understand and maximize the health benefits of apples. Phytochemical concentrations vary greatly between different cultivars. The level of some phytochemicals varies during maturation of the fruits in response to available light, stage of fruit development and to some types of fertilization. In general, storage of apples does not seem to greatly affect apple phytochemicals, but the processing of apples for juice results in a very significant decrease in phenolics. Processed apple peels retain their phenolic and flavonoid compounds activity and therefore may be used as a value-added ingredient with potent antioxidant activity.

The potential health benefits of apples are numerous. Regular consumption of fruits and vegetables, including apples, as part of a healthy diet may aid in the prevention of chronic disease and maintenance of good health.





Jeanelle Boyer and Rui Hai Liu

Department of Food Science and Institute of Comparative and Environmental Toxicology, Cornell University, Ithaca, New York 14853-7201 USA
Email: Jeanelle Boyer, This email address is being protected from spambots. You need JavaScript enabled to view it.; Rui Hai Liu, This email address is being protected from spambots. You need JavaScript enabled to view it.
Nutrition Journal 2004, 3:5 doi:10.1186/1475-2891-3-5

The electronic version of this article is the complete one and can be found online at: http://www.nutritionj.com/content/3/1/5

2004 Boyer and Liu; licensee BioMed Central Ltd. This is an Open Access article: verbatim copying and redistribution of this article are permitted in all media for any purpose, provided this notice is preserved along with the article's original URL.