Organic Acids in Peaches

Abstract

For greatest taste satisfaction from either fresh or processed peaches, the fruit must be picked and consumed as near to optimum maturity as possible. Flavor evaluation studies of canned cling peaches by Leonard, Luh, and Hinreiner (12) have shown that total titratable acidity in peaches decreases with maturation and that a fairly reliable indication of flavor rating is provided by the ratio of soluble solids to total acid in the raw fruit, when this value is referred to the total acidity. However, the nature of the organic acids in clingstone peaches was not investigated.Numerous studies of organic acids in freestone peaches have been published. Bigelow and Dunbar ( 3 ) reported that only malic acid was present in peaches. Nelson (18) found citric acid and malic acid present in almost equal proportions in canned peaches. Nuccorini and Cerri (21) found varying concentrations of malic, citric, and tartaric acids at different stages of development for both early-and late-ripening fruits. Peynaud (23, 24) investigated the nialic and citric acid composition of 36 varieties of peaches grown in France.Recently, Johnson, Foreman, and Mayer ( 1 2 ) reported the presence of chlorogenic acid in peaches. Gorse ( 5 ) discovered an isomer of chlorogenic acid, which he called neo-chlorogenic acid, i n ethyl acetate extracts of the Elberta and Halford varieties. Anet and Reynolds (1) isolated quinic acid from Golden Queen, J. H. Hale, and Blackburn Elberta peaches and indicated that this acid contributes greatly to the total acidity of the fruit. They also reported the presence of muck and galacturonic acids ( 2 ) in small amounts in the fresh fruit.The majority of the published information on organic acids in peaches, except the work by Anet and Reynolds ( l ) , was based either on precipitation of the organic acids as the barium salt in various concentrations of ethyl alcohol, or on esterification of the acids followed by fractional distillation. Under these conditions, separation of one acid from another may not be complete. Furthermore, no attempt was made t o correlate acid changes with an objective measurement of maturity.One of the programs of the Department of Food Technology a t Davis is concerned with factors influencing the quality of canned peaches. One phase of this program considers the importance of chemical constituents of the fruit. I n this work, the changes in major organic acids during the development of Halford and Peak clingstone and F a y Elberta freestone peaches were investigated by silicic acid column chromatography, using the method of Bulen, Varner, and Burrell ( 4 ) to determine acids in fruits. The results are correlated with the maturity of the peach as measured by pressure test. The importance of such changes t o the quality of canned peaches is discussed.

Organic Acid Changes During Ripening of Processing Peaches

“…1). This confirmed David et al (1956), Wills et al (1983a) and Chapman andHorvat (1990). However, Shenker andRieman (1953), Ryugo (1964), Ishida (1971), Souty and Andre (1975) and Meredith et al (1989) reported malic and citric acid were the only major organic acids in peaches.…”

“…Overall, 'Babygold 5' and 'Babygold 7' peaches rapidly increased in malic acid but very rapidly decreased in citric and quinic acid during ripening. A similar pattern was reported in 2 clingstone cultivars by David et al (1956). In an investigation of non-volatile acid changes in 'Monroe' peaches during fruit maturation (determined by capillary GC), Chapman and Horvat (1990) concluded that quinic was the major acid in immature fruits but rapidly decreased during maturation.…”

“…Malic is the predominant acid followed by citric and quinic acids; succinic have also been reported at very small quantities (Schenker and Rieman 1953;David et al, 1956;Ryugo, 1964;Ishida et al, 1971;Souty and Andre, 1975;Wills et al, 1983a;Meredith et al, 1989;Chapman and Horvat, 1990). However, Li and Woodroof (1968) reported that citric was the predominant acid in peaches, followed by malic acid.…”

“…Li and Woodroof (1968), Souty and Andre (1975), Meredith et al (1989) and Chapman and Horvat (1990) agreed that malic increased while citric acid decreased during ripening. David et al (1956) and Ishida et al (1971) reported that both malic and citric acid decreased during ripening.…”

“…Many qualitative and quantitative studies of organic acids in peaches have reported variable results because of different analytical methods used and/or peach cultivars studied (Schenker and Rieman, 1953;David et al, 1956;Ryugo, 1964;Li and Woodroof, 1968;Ishida et al, 1971;Souty and Andre, 1975;Wills et al, 1983a;Meredith et al, 1989;Chapman and Horvat 1990).…”