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Phenolic compounds in Rosaceae fruit and nut crops-A review Onwuchekwa Ogah, Sue Carolyn Watkins, Benjamin Ewa Ubi, and Nnadozie Oraguzie J. Agric. Food Chem., Just Accepted Manuscript • DOI: 10.1021/jf501574q • Publication Date (Web): 08 Sep 2014 Downloaded from http://pubs.acs.org on September 14, 2014

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Journal of Agricultural and Food Chemistry

Phenolic Compounds in Rosaceae Fruit and Nut Crops-A Review ONWUCHEKWA OGAH1

2

, CAROLYN S. WATKINS1, BENJAMIN EWA UBI2 AND

NNADOZIE C. ORAGUZIE1†

1

Department of Horticulture, Washington State University-Irrigated Agriculture and Extension

Center, 24106 N Bunn Road, Prosser, WA 99350, USA 2

Ebonyi State University, Abakaliki, Nigeria

†

Author to whom correspondence should be addressed.

Telephone: +1 509 786 9271. Fax: +1 509 786 9370. E-mail: [email protected]

1

ACS Paragon Plus Environment


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ABSTRACT

2

The demand for new fruit cultivars with high levels of phytochemicals, in particular phenolic

3

compounds, has received increasing attention from biochemists, pharmaceutical companies, plant

4

breeders and the general public due to their health benefits. This review focuses on economically

5

important Rosaceae which contains varying proportions and concentrations of these compounds. The

6

paper discusses the common phenolics in the Rosaceae including phenolic acids, flavonols, flavanols,

7

anthocyanins, and dihydrochalcones. The non-extractable phenolics are also presented but not

8

discussed in detail.

9

environmental factors that affect their concentration and composition, are highlighted. Further, we

10

present the different approaches for biofortication and posit that breeding may be the most viable and

11

sustainable option as it improves other fruit quality traits simultaneously and increase confidence in

12

adoption of new cultivars with enhanced consumer appeal.

The metabolism and bioavailability of phenolics, as well as human and

13 14

KEYWORDS: Rosaceae, phenolic acids, flavonoids, flavanols, anthocyanins, dihydrochalcones,

15

non-extractable phenolics (NEPP), environmental influence, metabolism, bioavailability,

16

biofortification

2


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INTRODUCTION

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Fruits, nuts, and vegetables have been noted to play significant roles in human health and nutrition,

19

especially as sources of phytochemicals and other bioactive compounds. Amongst these plants are the

20

rosaceous fruit and nut crops. The Rosaceae is the 19th largest family of plants 1 and includes ~95 to

21

more than 100 genera and 2830−3100 species. 1 Of economic importance are members such as apple,

22

pear, quince, almond, peach, apricot, plums, cherries, etc. The total world production of edible

23

rosaceous fruits in 2005 based on FAO statistics is ~113 million tons. 2 At a very conservative farm

24

gate value of US $400 per ton, this translates to $45 billion. With the world value of almonds, cut

25

roses, rose plants, and other products included, the Rosaceae could be worth at least $60 billion

26

annually at the farm gate, with a consumer value of triple this amount, totaling ~$180 billion.1

27

Members of this family provide high-value nutritional foods and contribute desirable aesthetic and

28

industrial products. Several studies have emphasized that Rosaceae fruits and nuts can exert a

29

protective effect against human degenerative diseases such as cardiovascular disease, diabetes,

30

obesity, etc.

31

compounds.

1

This is due to their inherent richness in various phytonutrients including phenolic

32

Phenolic compounds are secondary plant metabolites characterized by at least one aromatic

33

ring with one or more hydroxyl groups attached. Plant phenolics are synthesized from carbohydrates

34

via the shikimate and phenyl propanoid pathways, and are generally produced as defense mechanisms

35

against pathogens and disease organisms, protection from excess ultraviolet radiation and as

36

attractants for pollinators. Complex phenolic compounds are also important structural components of

37

plants.

38

The most important groups of phenolics in plants are the flavonoids, phenolic acids, lignans

39

and stilbenes. The flavonoid group can be subdivided into seven categories including flavonols, 3



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flavones, isoflavones, flavanols, flavanones, anthocyanins and dihydrochalcones, of which flavonols,

41

flavanols, anthocyanins, isoflavones, and dihydrochalcones are found in the Rosaceae.

42

representatives of flavonols, including quercetin and kaempferol, are present in glycosylated forms

43

and the associated sugar moiety is often glucose or rhamnose. Flavanols are not glycosylated, and

44

exist in both the monomer form (catechins) and the polymer form (proanthocyanidins or condensed

45

tannins). Catechin and epicatechin are the main flavanols in rosaceous fruits and are the building

46

blocks for dimeric, oligomeric and polymeric procyanidins. Anthocyanins are pigments dissolved in

47

the vacuolar sap of usually the epidermal tissues of fruits and exist in a range of chemical forms that

48

are blue, red, purple, pink or colourless according to the pH. Cyanidins and pelargonidins are the

49

most common anthocyanins in foods. Dihydrochalcones are a family of the bicyclic flavonoids,

50

defined by the presence of two benzoid rings joined by a three-carbon bridge. Phloridzin, which

51

belongs to the dihydrochalcone family, is present in some rosaceous fruits.4,5.

3-5.

The main

52

Two classes of phenolic acids can be distinguished including derivatives of benzoic acid and

53

cinnamic acid. These acids are found in plants in both free and esterified forms with sugars and other

54

organic acids. 6.Hydroxycinnamic acids are more common than hydroxybenzoic acids, with the main

55

compounds of the hydroxycinnamic acid class including p-coumaric, caffeic, and chlorogenic acids.

56

Hydroxybenzoic and hydroxycinnamic acids are also components of complex structures such as

57

hydrolysable tannins (gallotannins and ellagitannins) and lignins, respectively.

58

Studies in animal subjects have demonstrated that phenolics are bioavailable and exert a

59

protective role against oxidative stress and free radical damages. Oxidative damage triggered by free

60

radicals can cause structural and functional alterations of cell macromolecules leading to molecular

61

mechanisms instrumental in human chronic diseases. Epidemiological studies have suggested that

62

phenolic compounds such as flavonoids, phenolic acids, anthocyanins and carotenoid compounds 4


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including quercetin, kaempferol, myricetin, p-coumaric acid, gallic acid, and ellagic acid can act as

64

antioxidants and/or cancer-inhibiting compounds, and thus may be involved in the prevention of

65

degenerative diseases such as epithelial (but not hormone-related) cancers and cardiovascular

66

diseases, Type II diabetes, thrombotic stroke, obesity and neurodegenerative diseases associated with

67

aging and infections. 7.Although phenolic compounds have long been studied for their antioxidant

68

properties, which are now well-characterized in vitro, recent studies have stressed that the

69

mechanisms of biological actions of phenolics extend beyond their antioxidant properties. It is now

70

believed that phenolics may exert their beneficial action through modulation of gene expression and

71

the activity of a wide range of enzymes and cell receptors; however, the health effects of dietary

72

phenolics depend on the amounts consumed, their chemical structure and bioavailability. 8 Although

73

polyphenols are ubiquitous in rosaceous plants, their content, distribution, bioavailability and identity

74

vary depending on genetics, fruit location, plant structure, pre-harvest and post-harvest factors and

75

climatic conditions. In this review, we will discuss the common phenolic compounds (and briefly

76

summarize the newly-emergent exploration into non-extractable phenolics) identified in

77

representative Rosaceae crops in five sub-groups, their health benefits, pre- and post-harvest factors

78

as well as climatic conditions that affect their amount and concentration. Finally, we will discuss their

79

bioavailabilty and profer suggestions on possible methods for biofortification to increase consumer

80

appeal and enhance fruit consumption.

81 82

ECONOMIC AND HEALTH BENEFITS OF ROSACEOUS FRUIT AND NUT CROPS

83

Rosaceae is the 19th largest plant family, comprising than 90 genera with over 3000 distinct

84

species and having a cosmopolitan distribution, being found just about everywhere except Antarctica.

85

Four sub-families are distinguished based on fruit type including the Maloideae (apples, loquat, 5



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quince, pear), the Prunoideae (Prunus being the largest genus of Rosaceae with cherries, plums,

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peaches, apricots and almonds among the representative fruit), the Rosoideae (roses, strawberries,

88

blackberries and raspberries) and the Spiraeoideae. Rosaceous crops (some examples previously

89

mentioned) contribute to human health and well-being and provide an economic foundation for many

90

rural communities in North America. 1,2.

91

Included in the Rosaceae family is a huge variety of edible fruit and nut crops as well as

92

highly valued ornamental trees and shrubs. Consumers prefer a wide range of choice in their

93

purchases of produce or processed foods, and the Rosaceae provides it with colorful and flavorful

94

health-promoting fruits and nuts. A huge variety of textures and flavors can be found in fruits from

95

this family which can be purchased fresh or processed. 1 In addition to the gustatory variety provided

96

by these crops, rosaceous fruits provide a major source of dietary phytochemicals (flavonoids and

97

other phenolic compounds) purported to promote health by mitigating oxidative stress and

98

inflammation which can ultimately lead to chronic disease. Some well-known antioxidants and/or

99

cancer-inhibiting compounds that have been identified in the Rosaceae are ascorbic acid, quercetin,

100

kaempferol, myricetin, p-coumaric acid, gallic acid, and ellagic acid.

101

Ellagic acid present in Rosaceae members such as strawberry, red raspberry, cloudberry,

102

apple, pears and other rosaceous fruits has been shown to affect cell proliferation and apoptosis in

103

human pancreatic adenocarcinoma cell lines, suggesting a potential anticancer role.

104

examination of 728 men aged 65–84 in the Zutphen Elderly Study

105

were shown to have a significant effect in the reduction of epithelial cancer. The same study showed

106

that tea, which contributed 87% of the total catechin intake, has a lesser effect in decreasing epithelial

107

lung cancer when compared to apple, which contributed only about 8% of the catechin consumption.

108

Further, the intake of rosaceous fruits also reduces the risk of cardiovascular disease. For example, 6


10

9

Following the

dietary rosaceous catechins

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the role of anthocyanins in cardiovascular disease includes protecting lipids from oxidant damage

110

thereby aiding in the prevention of cardiovascular vessel plaque formation, providing anti-

111

inflammatory action, induction of nitric oxide formation leading to vascular dilation, etc. Prior et al.11

112

reported that the consumption of 280 g of cherries (the equivalent of ~28 “Bing” sweet cherry fruits)

113

caused a statistically significant increase in plasma lipophilic antioxidant capacity that is

114

approximately seven times greater compared to the control. Tabak et al.

115

12

have demonstrated a beneficial relationship between consumption of catechin

116

from solid fruit (apple/pear) and general pulmonary health. The study, consisting of over 13,000

117

adults in the Netherlands, observed a positive correlation between consumption of solid fruit

118

(especially apple and pear) and increase in pulmonary function/decrease in symptoms of COPD. A

119

separate study of approximately 2,500 middle-aged men (age 45–59 years) suggested a strong

120

positive correlation between apple consumption and lung function as measured by forced expiratory

121

volume in one second (FEV1).

122

body mass index, social class and exercise, the consumption of fresh apple remained positively

123

correlated with lung function while consumption of citrus fruit and/or fruit juices did not. Greater

124

FEV1 of 138 mL was recorded for those who consumed five or more apples per week when compared

125

to those who did not consume apple.

13

Following adjustment for confounding influences such as smoking,

126

De Oliveira et al. 14.reported that a high intake of quercetin, a major component of rosaceous

127

fruits, was associated with a decreased risk of Type II diabetes. In addition, intake of myricetin,

128

common in rosaceous fruits such as strawberry, may also decrease the risk of Type II diabetes.

129

Although evidence is limited on the protective role of cherry in diabetes, a few researchers have

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reported the role of cherry anthocyanins in reducing insulin resistance and glucose intolerance.

131

15

.Sweet cherry has a relatively low glycemic index of 22 compared to other fruits such as grapes, 7



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which scored 46. This lower glycemic index makes sweet cherry a potentially better fruit-based snack

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food for people with diabetes.

134

Cyanidins and malvidin, which are very abundant in sweet cherry and other rosaceous fruits,

135

have been shown to inhibit the cyclooxygenase (COX) enzymes responsible for inflammatory

136

response. Thomson and Kubota 16 suggested that flavonoids and proanthocyanidin compounds, which

137

are common in rosaceous plants, in particular, cherries, might reduce oxidative stress and amyloid

138

production thereby reducing the risk of Alzheimer’s disease. Rosaceous fruits contain a large number

139

of antioxidants (free radical neutralizers) that purportedly help prevent arthritis and brain

140

dysfunctions. The accumulation of uric acid (the primary cause of gouty arthritis) and other toxic

141

substances in the body is one of the ill effects of un-neutralized free radicals. Consumption of

142

rosaceous produce, extremely abundant in anti-oxidants, can effectively help alleviate such health

143

hazards. Memory decline and loss of limb control are common in older individuals due to aging of

144

the brain and the nervous system, facilitated, at least in part, by the action of free radicals present in

145

the system. Dietary phenolics provide an additional mechanism of neutralizing the effect of these

146

oxidants, thereby serving to protect the system.

147

A recent study 17 with mice implanted with aggressive breast cancer cells, the MDA-MB-435,

148

demonstrated an inhibition of a marker gene in the lungs after a few weeks of being fed with peach

149

extracts containing a mixture of phenolic compounds. This mixture of phenolic compounds was

150

believed to be responsible for the tumour growth inhibition and metastasis in mice. The authors

151

suggested that the dose necessary to see these effects in mice will be equivalent to the consumption of

152

two to three peaches per day by humans.

153 154 8


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PHENOLIC COMPOUNDS IN ROSACEAE FRUITS AND NUT

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The five major phenolic compounds including pheolic acids, flavanols, flavanols, anthocyanins and

157

dihydrochalcones will be discussed within each rosaceous crop as follows:

158

Apple (Malus x domestica Borkh.). Apple is a good source of phytochemicals including phenolic

159

acids, anthocyanins, flavan-3-ols and flavonols. 6.No wonder the saying ‘an apple a day keeps the

160

doctor away’!

161

(neochlorogenic, cryptochlorogenic and chlorogenic acids, respectively)] and 3-coumarylquinic acid

162

with chlorogenic acid as the main phenolic acid in apple juice. Minor phenolic acids identified and

163

characterized are presented in Figure 1.

164

on cultivar, with cider varieties in general having a higher phenolic acid concentration than dessert

165

apples. 18

Major apple phenolic acids include 3-,4-, and 5-caffeoylquinic acid [(CQA),

5,6,18-20

.The concentration of phenolic acids varies depending

The major flavonols are quercetin glycosides (arabinose, galactose, glucose, rhamnose and

166

18,21,22

167

rutinose) and kaempferol and are found mainly in the peel (Figure 2).

As with phenolic acids,

168

apple cider varieties have a higher concentration of flavonols than dessert apples. For example, the

169

average quercetin glycoside content in the peel and pulp of a dessert apple is 6.8 mg/100 g while

170

cider apple peel and pulp contain 5.7 mg/100 g of quercetin glycoside. 18

171

Flavan-3-ol compounds, also called flavanols, exist in both the monomer form (catechins) and

172

the polymer form (proanthocyanidins) in apple. Many such compounds exist in apple (see Figure 2).

173

23,24

174

dimer B2.

175

having a comparatively high content of procyanidins which are particularly responsible for their

176

astringency and bitterness. Procyanidins are found in the whole apple fruit and their levels gradually

177

increase from 1,232 mg/kg in the seeds to 4,964 mg/kg in the epidermal tissue of the fruit.

and apple is a rich source of (-)-epicatechin, (+)-catechin, and procyanidin (a proanthocyanidin) 24

The concentration of flavanols varies from one variety to the other, with cider apples

9


25,26

The


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concentration of flavan-3-ols in apple is often affected by preparation methods. For example, only

179

about 3% of the catechins are recovered in the juice, whereas a majority is retained in the pomace. 27

180

Pure juice of dessert apple contains ~7.8 mg/100 mL (-)-epicatechin while pure juice of cider apple

181

contains ~9.0 mg/100 mL of (-)-epicatechin.

182

Some apple cultivars do not produce high anthocyanins in their skin except under high

183

sunlight. Examples include “Granny Smith” and “Golden Delicious”. The main anthocyanins are

184

cyanin derivatives such as cyanidin 3-galactoside (cy3-gal), cyanidin 3-glucoside (cy3-glu), cyanidin

185

3-arabinoside (cy3-ara), and cyanidin 3-xyloside (cy3-xyl) (Figure 4). Cyanidin 3-galactoside (cy3-

186

gal) is the major pigment accounting for 80% of the total anthocyanins in apple. 28-30

187

Studies including those of Spanos et al.

31,32

and Tomás-Barberán et al.

33

have shown that

188

dihydrochalcone derivatives such as phloridzin (phloretin 2-O-D-glucoside) and phloretin 2-O-(6-D-

189

xylosyl)-D-glucoside are major constituents of apple.

190

phloretin xyloglucoside are much lower in concentration. Vrhovsek et al.

191

dihydrochalcones while Lee et al.

192

Phloridzin is highly concentrated in the seeds, representing 98% of seed flavonoids. 36 Awad et al.

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reported 10 times more phloridzin in seeds than in the skin and 100 times more than in the flesh.

194

Gosch et al. 38 observed more than 90% phloridzin in the soluble phenolic compounds extracted from

195

apple leaves. The high concentration of dihyrochalcones in apple makes apple unique among the

196

Rosaceae as very low amounts (or none, as in pear) are found in other rosaceous fruit.

197

Sweet cherry (Prunus avium L.) and tart cherry (Prunus cerasus L.). Although sweet cherry and

198

sour cherry have small fruit in comparison to other Prunus species including peach, nectarine,

199

apricot, plum, etc., they contain a relatively high amount of phytochemicals. Phenolic acids in

200

cherries have been characterized by different authors and have been summarized by Macheix et al. 39

35

However, phloretin xylogalactoside and 34

reported 2-6% of

found 5.59 mg/100 g of phloretin glycosides in apple fruit.

10


37

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and listed in Figure 1. Sweet cherry contains about 70-80% hydroxycinnamic acid esters 40 with

202

neochlorogenic acid (3-CQA) and 3'-p-coumaroylquinic acid being predominant. The ratio of

203

neochlorogenic acid to 3'-p-coumaroylquinic acid differs among cherry cultivars as well. For

204

example, “Bing” a mid-season variety, contains 60% neochlorogenic acid and 40% 3'-p-

205

coumaroylquinic acid while “Burlat” (a founder variety for many modern early cultivars) contains

206

16.5% neochlorogenic acid and 75% 3'-p-coumaroylquinic acid. 41

207

Flavonols, particularly quercetins and kaempferols, are found in high concentrations in cherry

208

(Figure 2). Both sweet cherry and sour cherry contain a high number and concentration of flavonols

209

when compared to other rosaceous fruits with the majority consisting of glycosylated quercetins and

210

kaempferols (see Figure 2).

211

differences mainly attributable to the sugar moiety of the derivative; for example, kaempferol-3-

212

rhamnosyl-4'-diglucoside as opposed to kaempferol-3-rutinosyl-4'-diglucoside, and quercetin-3-

213

galactosyl-7-diglucoside as opposed to quercetin-3-rutinosyl-7,3'-diglucoside, etc (see Figure 2). 40,44

42,43

Both sour and sweet cherry share many of the same flavonols with

214

Sweet cherry and sour cherry contain flavanols including catechins, epicatechins,

215

gallocatechin and epigallocatechin (Figure 3). 39 The 2013 USDA Database for the flavonoid content

216

of selected food reports that catechin and epicatechin values of raw sweet cherries are 4.4 and 5.0

217

mg/100g, respectively, which is higher than in pear, quince, raspberry or strawberry.

218

results are corroborated in an independent study by Henning and Hertmann

219

epicatechin content of 4.8 mg/100g in sour cherry.

47

45,46

These

who reported an

220

Different authors have identified and characterized major anthocyanin pigments in sweet and

221

sour cherries. The eight anthocyanins identified are listed in Figure 4 and consist mainly of the

222

glucosides and rutinosides of cyanidin, pelargonidin and peonidin.

223

main anthocyanin in sweet cherry representing 84% of the total anthocyanins with cyanidin-311


40

Cyanidin-3-rutinoside is the


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glucoside making up most of the remainder. However, a different anthocyanin profile exists in sour

225

cherry. Sour cherry contains all the anthocyanidins found in sweet cherry except pelargonidin-3-

226

rutinoside, in addition to the following cyanidins unique to sour cherry: cyanidin 3-O-glucosyl-

227

rutinoside, cyanidin 3-O-sophoroside, cyanidin 3-O-arabinosyl-rutinoside and cyanidin 3-O-

228

gentiobioside.

229

50

230

80% of the total anthocyanins

231

flesh. Gao et al.

232

skin, flesh and pit, with the pit having higher concentrations. However, skin pigmentation may not in

233

most cases qualify as a determinant of anthocyanin concentration. For example, “Bing” has

234

pigmentation in the flesh while other cherries such as “Royal Ann” (sweet cherry) and

235

“Montmorency” (sour cherry) do not.

236

and flesh (about 79% and 56%, respectively) while “Bing’s” pit contains mainly cyanidin-3-glucoside

237

(about 51%). Anthocyanins are absent in the flesh of “Montmorency”, “Royal Ann”, and “Rainier”

238

cherries. The distribution of cyanidin-3-sophoroside (unique to sour cherries) differs from that of

239

other anthocyanins in that it is present in a higher proportion in “Montmorency” pit than in the skin.

240

Plum (Prunus domestica L.). Both dried and fresh plums are rich sources of nutritive and bioactive

241

compounds among which is phenolic acid.

242

varieties has higher amounts of phenolic acids than fresh plum due to concentration during the drying

243

process despite partial degradation. Generally, plum varieties contain high quantities of

244

hydroxycinnamic acids, especially neochlorogenic acid, with hydroxycinnamates (caffeoylquinic

245

acids) constituting 86% of the total phenolic acids in plum.

246

acids in plum and prune are listed in Figure 1.

48,49

Cyanidin-3-arabinosylrutinoside has been detected only in “Balaton” sour cherry.

The predominant anthocyanin in sour cherry is cyanidin-3-O-glucosyl-rutinoside which represents

42

40

Generally, the skin contains higher anthocyanins than the pit and

reported that ‘Bing’ was the only sweet cherry containing anthocyanins in the

40

Cyanidin-3-rutinoside is the major anthocyanin in the skin

However, dried plum (prune) from prune-making

50

Identified and characterized phenolic

12


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Sultana et al.

51

detected 564.8 mg/kg of total flavonols in plum while Justesen et al.

52

248

reported 1.5 mg/100 g of quercetin, 564.1 mg/kg of myricetin, and 0.7 mg/kg of kaempferol. The

249

flavonol glycosides found in plum include 3-glucosides, 3-galactosides, 3-rutinosides, and 3-

250

arabinoside-7-rhamnosides of quercetin and kaempferol.

251

major quercetin constituting about 2% of all phenolics in plum. 47 The major and minor contributors

252

to flavonol content in plum can be found in Figure 2.

39

Quercetin-3-rutinoside appears to be the

253

The main flavan-3-ols in plum are catechins, procyanidin B1, procyanidin B2, procyanidin

254

B3, epicatechin and procyanidin B4 (Figure 3).53 The same authors also reported the availability of

255

A-type dimers and trimers in smaller concentrations. According to Donovan,

256

proanthocyanidins, contributing about 70% of the total polyphenols in plum. Fresh plum contains

257

flavan-3-ols in the range of 20–40 mg/kg.

258

mg/100g of catechin and 2.84 mg/100g of epicatechin.

56

The peeled plum contains flavan-3-ols in

259

the range of 662–1837 mg/kg (as catechin equivalent).

56

The concentration of catechins increases

260

with fruit development and decreases when the fruit reaches maturity. 57

55

54

plum is rich in

The edible portion of plum has an average of 3.35

261

Anthocyanins include cyanidin 3-O-rutinoside, cyanidin 3-O-glucoside and peonidin 3-O-

262

rutinoside (Figure 4). Anthocyanins have not been detected in prune and prune juice.54 The total

263

anthocyanin content ranges from 18 to 125 mg/100 g in fresh weight.54,58,59 Cyanidin-3-rutinoside is

264

predominant in plum (14.1-33.0 mg/100 g) while cyanidin-3-glucoside and peonidin-3-rutinoside are

265

minor ranging between 1.9-13.5 mg/100g and 1.1-1.2 mg/100 g, respectively. 59

266

Apricot (Prunus armeniaca L.). Apricot contains a signiﬁcant amount of phenolic acids which

267

contribute to its nutritive value. The major phenolic acids are 3-CQA and 5-CQA, with 5-CQA being

268

more dominant.

60

Sochor et al.

61

also confirmed that 5-CQA is the principal phenolic acid. See

13



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Figure 1 for identified phenolic acids in apricot. Processed and unprocessed apricots share similar

270

qualitative phenolic acid profiles although lower quantities are found in the processed products.

271

The flavonols occur mostly as glucosides and rutinosides of quercetin and kaemferol, with 39

272

quercetin 3-rutinoside being the most identified in various cultivars (Figure 2).

273

level in apricot was estimated at 784.8 ± 32.6 mg/kg dry weight while the concentrations of

274

myricetin, quercetin, and kaempferol were 406.9 ± 16.3; 322.1 ± 6.4; 5.8 ± 0.2 mg/kg dry matter,

275

respectively. 51.

276

The total flavonol

Flavan-3-ol is one of the major phenolic compounds in apricot with (+)-catechin and (-)56

277

epicatechin being the most important flavan-3-ols.

The concentrations of (-)-epicatechin in the

278

fruit and jam are 4.6 mg/100 g and 0.5 mg/100 g, respectively while (+)-catechins concentrations are

279

3.9 mg/100g in the fruit and 0.4 mg/100 g in the jam.

280

procyanidin B2, and procyanidin B3 (Figure 3). 61,62 Processed and unprocessed apricots share similar

281

qualitative profiles although lower quantities are found in the processed products.

36

The fruit also contains procyanidin B1,

282

The study of anthocyanins in apricot seems relatively rare, since the orange color of the un-

283

blushed side of the fruit is conferred by carotenoids. However, a study by Bureau et al. 63 looked at

284

anthocyanin concentrations during ripening in two red apricot accessions. In addition to the presence

285

of cyanidin-3-O-rutinoside (representing 75% of the total anthocyanins detected), these authors also

286

found cyanidin-3-O-glucoside and peonidin-3-O-rutinoside at concentrations of approximately 12%

287

each. Their study was the first to identify peonidin-3-O-rutinoside in apricot fruit. Figure 4 lists

288

anthocyanins found in some apricot varieties.

289

Peach and Nectarine (Prunus persica L.). Peach and nectarine are similar in appearance and color,

290

although they differ by a single gene for skin texture. They possess similar qualitative and

291

quantitative phenolic acid profiles. Phenolic acids include chlorogenic acid, neochlorogenic acid, 14


Page 15 of 63


292

gallic acid and caffeic acid (Figure 1). The major phenolic acid is 5 CQA, which is about 15.6

293

mg/100 g in peach peel and cortex, 5.3 mg/100 g in peach cortex, 6.1 mg/100 g in nectarine peel and

294

cortex and 8.2 mg/100 g in nectarine cortex. 36 Peach and nectarine also contain a good amount of 3-

295

CQA (8.8 mg/100 g in peach peel and cortex, 4.1 mg/100 g in peach cortex, 4.0 mg/100 g in

296

nectarine peel and cortex, and 5.1 mg/100 g in nectarine cortex).

297

concentrations of 5-CQA, 3-CQA and caffeic acid decreased significantly in various peach cultivars

298

sampled during the ripening process in New York State in 1987 and 1988, from a high at green

299

immature stage (mid-July) to a level approximately 25% that value at harvest (mid-September).

300

36

Lee et al.

64

reported that the

Major flavonols include quercetin glucosides and galactosides (Figure 2). Chang et al.

65

301

observed malvidin 3, 5-0-diglucoside (malvin), quercetin 3-0-rutinoside (rutin), and quercetin 3-0-

302

glucoside (isoquercetin). These authors also reported that rutin and isoquercetin were the primary

303

flavonols found in peach particularly, in the peels rather than in the flesh.

304 305 306

Peach and nectarine share similar flavan-3-ol profiles including catechins, epicatechin, procyanidin B1, and procyanidin B2 (Figure 3). 53 The main anthocyanins in peach are cyanidin-3-glucoside and cyanidin-3-rutinoside with the 66

307

former being the most predominant (Figure 4).

308

higher anthocyanin contents than those with white or yellow flesh. 67 The anthocyanin content ranges

309

from 6.0–37 mg/100 g.

310

Pear-European pear (Pyrus communis L.) and Asian pear (P. pyrifolia Nakai.). Pear has a similar

311

phenolic acid profile to apple, the major difference being (in pear) the presence of arbutin (a

312

hydroquinone glucoside) and the lack of phloretin derivatives.

313

be exploited as a chemical marker for pear in cases where suppliers might be tempted to cut apple

314

juice with less expensive cider pear juice.

68

Peach cultivars with dark red colored flesh have

32

In fact, the presence of arbutin can

Identified and characterized pear phenolics are 15



69

46

315

summarized in Figure 1.

316

hydroxycinnamic ester while Spanos et al. 32 found chlorogenic acid to predominate with caffeic acid

317

making a respectable second-place appearance.

reported that chlorogenic acid was the major

Pear contains several quercetins and isorhamnetins including their glycosides. 69 See Figure 2

318 319

Amiot et al.

Page 16 of 63

for a summary of major and minor flavonol constituent of pear. Studies have shown that pear contains 96% flavan-3-ol. Galvis-Sanchez et al.

320

46

69

reported

321

flavanols, particularly procyanidins, in the peel and not in the flesh.

322

epigallocatechin, gallate and proanthocyanidins have also been reported in pear (Figure 3).70,71 Amiot

323

et al. 46 reported concentrations of 0.6–8.7 mg/100 g and 0-0.5 mg/100 g for epicatechin and catechin,

324

respectively, while Risch et al.

325

mg/kg for catechin.

72

reported concentrations of 5–60 mg/kg for epicatechin and 0–10

The major procyanidins in “Bartlett” are B1 and B2.

326

Catechin, epicatechin,

32

Red pear skin contains cyanidins and

327

peonidins (Figure 4). 71,73,74 Cyanidin-3-galactoside is the main anthocyanin in red pear with a relative

328

percentage of 63% while the second main anthocyanin is peonidin 3-galactoside. 73 Galvis-Sanchez et

329

al. 69 reported that the peels of “Red D’Anjou” and “Forelle” contain 12.0 mg/100 g and 1.2 mg/100 g

330

anthocyanins, respectively. The study also confirmed cyanidin 3-O-galactoside as the main pigment.

331

Quince (Cydonia oblonga Miller.). Studies have shown that quince is a natural source of phenolic

332

acids (Figure 1).71,745,75 Quince fruit is very firm, acidic and astringent, and not well suited to raw

333

consumption in the human diet. In Portugal a major use of the fruit is in the production of jams and

334

jellies.

335

CQA’s, 3,5-O-diCQA and two glycosylated quercetins. Quince peel contains the same six phenolic

336

compounds as the pulp (but at a much higher concentration) plus seven flavonol derivatives, which, if

337

detected in a jam product, can be used as an indicator of adulteration with unpeeled fruit. 77.

76

Six phenolic compounds can be found in quince pulps including 3-O-, 4-O-, and 5-O-

16


Page 17 of 63


The concentration of phenolic acids in quince foodstuffs varies depending on the final

338

77

339

product. According to the observations of Silva, et al.

, 3-CQA can be found in quince pulp at a

340

concentration of about 3.7 mg/100g, but approximately 62% of this is lost in jam-making with an

341

additional loss of 27% in jelly making. Cryptochlorogenic acid (4-CQA; concentration in pulp is ~0.5

342

mg/100 g) fares a little better, with no significant loss from fruit to jam, and a 60% loss from fruit to

343

jelly. The fate of 5-CQA (~8.6 mg/100g in pulp) is similar to 3-CQA. With respect to 3,5-diCQA

344

(0.6 mg/100 g in pulp), only about 34% is lost from fruit to jam. 36, 77.

345

According to Silva et al. 76,77 and Andrade et al.71, quince contains glycosides of quercetin and

346

kaempferol, and quercetin and kaempferol glycosides acylated with p-coumaric acid (Figure 2).

347

Quince peel contains five phenolic compounds in common with the pulp, and, in addition, kaempferol

348

3-glucoside, kaempferol 3-rutinoside and several partially identified compounds including

349

kaempferol glycosides, quercetin glycosides acylated with p-coumaric acid and kaempferol

350

glycosides also acylated with p-coumaric acid. Higher concentrations of quercetin-3-O-rutinoside are

351

found in the peel than in the pulp. 77.

352

Nine flavan-3-ols, mainly (-)-epicatechin, procyanidin B2, three procyanidin dimers and

353

trimers, and one tetramer have been identified and characterized (Figure 3). 78 Flavan-3-ols constitute

354

between about 78% and 94% of the total polyphenolic compounds in quince. 79 Unlike apple, cherry and pear, quince is low in anthocyanins. However, Markh et al.

355

79

356

reported two anthocyanins in red quince including cyanidin-3-glucoside and cyanidin-3-3, 5

357

diglucosides (Figure 4).

358

Almond (Prunus dulcis Mill. syn P amygdalus). The phenolic acid content of almond has been

359

associated with astringent taste, discoloration, inhibition of enzyme activity and antioxidant activities.

360

81

Various investigators have isolated and characterized phenolic acids in almond. 80-82 Most of these 17



Page 18 of 63

361

studies noted that the phenolic acid content occurs in the form of soluble esters and free phenolic

362

acids. 81 It was observed that the total amount of free phenolic acid is ~16.3 µg/g in the skin while the

363

total amount of esterified phenolic acid in the skin, shell and whole seed extract were ~279.6 µg/g,

364

167.1 µ/g and 40 µg/g, respectively. These phenolic acids are summarized in Figure 1

365

mainly benzoic acid or cinnamic acid derivatives. Glycosides of protocatechuic acid and vanillic p-

366

hydroxybenzoic acid are common in the skins.

367

glycosides of kaempferol and isorhamnetin while the skin and kernel largely contain quercetin-3-O-

368

galactoside, kaempferol glycosides (as in seed), and isorhamnetin glycosylated with galactose instead

369

of glucose.

370

acid (4-CQA) and neochlorogenic acid (5-CQA). 84

82,83

82

80,81

and are

The seed contains mainly rutinose- and glucose-

The hulls also contain chlorogenic acid and its isomers such as cryptochlorogenic

371

Glycosides of quercetin, kaempferol and isorhamnetin have been identified in almond by

372

several researchers, and their consolidated findings can be viewed in Figure 2.85,86 According to

373

Milbury et al.

374

California almonds is isorhamnetin (as the 3-O-rutinoside or 3-Oglucoside), representing about 70%

375

of the total, followed by catechin, kaempferol-3-O-rutinoside, epicatechin, quercetin-3-O-galactoside,

376

and isorhamnetin-3-O-galactoside. The seed contains the majority of kaempferol- and isorhamnetin-

377

3-O- rutinosides and glucosides while the skin and kernel contain quercetin- and isorhamnetin- 3-O-

378

galactoside in addition to the conjugates found in the seed. 86

379

85

, the predominant flavonoid across eight varieties tested in their examination of

Information on anthocyanin content of almond is limited but at least one report has suggested

380

the presence of cyanidin and delphinidin (Figure 4). 86.

381

Raspberry and Strawberry (Rubus spp and Fragaria species). Raspberries and strawberries

382

contain significant amounts of phenolic acids (Figure 1). Ellagic acid and its conjugates such as

383

ellagic acid arabinoside, ellagic acid acetyl-xyloside, and ellagic acid acetyl-arabinoside are the most 18


Page 19 of 63


384

predominant phenolic acids in red raspberry. 87-89 However, this is quite different in strawberry,

385

where the major phenolic acids are p-hydroxybenzoic acid and p-coumaric acid. 90 Berries also

386

contain ellagitannins with the highest content in red raspberry and strawberry. 91,92 The ellagitanins

387

found in raspberry include sanguiin H6, lambertianin C, and sanguiin H10. 36 Recent studies 93

388

reported two other compounds, bis-hexahydroxydiphenoyl-glucose (bis-HHDP-glucose) and galloyl-

389

HHDP-glucose, in four cultivars including Jewel, Mira, Kent and St. Pierre. The author observed

390

higher concentrations of bis-HHDP-glucose in “Mira” than in other cultivars while no significant

391

differences were observed in galloyl-HHDP-glucose among cultivars. Flavonols such as quercetin and kaempferol, including their glycosides, have been reported.

392 393

87,90

394

raspberry (Figure 2). These studies also indicated that quercetin-3-glucuronide was the major flavonol

395

in red raspberry juice. The flavonol profile of strawberry is similar with the exception of the

396

predominance of kaempferol and the presence of myricetin in strawberry. Mahmood et al.

397

reported that kaempferol was the dominant flavonol in strawberry followed by myricetin and

398

quercetin.

399

Mullen et al.87, in particular, reported the presence of various quercetins and kaempferols in

90

also

There is limited information on raspberry and strawberry flavanols. However, Määttä 93

and Gu et al.

94

400

Riihinen et al.

reported that strawberry and raspberry proanthocyanidins occur in

401

the form of procyanidins and propelargonidins. Flavanols isolated and characterized in both

402

strawberry and raspberry include catechins, epicatechin, procyanidin B1 and procyanidin B2 (Figure

403

3). Lesser amounts of proanthocyanidins are found in strawberry compared to raspberry and other

404

berries. De Pascual-Teresa et al. 95 and Pallauf et al. 96 have reported that the values of raspberry and

405

strawberry flavanols ranged from 2-48 and 10-29 mg/100 g FW, respectively.

19



Page 20 of 63

406

The berries of Rosaceae, in particular strawberry and raspberry, are among the lowest in

407

anthocyanin content compared to berries such as chokecherries, gooseberries, blueberries, etc. The

408

anthocyanins in strawberry and raspberry are principally the glycosides of cyanidin and pelargonidin

409

(Figure 4).

410

rutinose, and, to a lesser extent, sophorose.

411

anthocyanins in red raspberry. The main anthocyanin in black raspberry is cyanidin 3-(6'-p-

412

coumaroyl)-glucoside. 99 Pelargonidins in the form of pelargonidin 3-O-glucoside and pelargonidin 3-

413

O-(6'-succinyl-glucoside) are also found in strawberry. Borges et al.

414

glycosylated cyanidins and pelargonidins, along with delphinidin and malvidin, in raspberry, (see

415

Figure 4). Cyanidin-3-O-sophoroside was characterized as the major anthocyanin in raspberry, at

416

42% of the total.

97,98

The anthocyanins in raspberry are glycosylated with glucose, galactose, arabinose or Cyanidin derivatives (sophorosides) are the major

98

identified variously-

417

The anthocyanin profile in strawberry is quite different from raspberry, as the majority of

418

strawberry anthocyanins are pelargonidins with pelargonidin-3-glucoside representing 71% of the

419

total. 97.

420 421

Although dihydrochalcone is more common in apple, Hilt et al.

100

reported the presence of

phloridzin in strawberry.

422 423

NON-EXTRACTABLE POLYPHENOLS (NEPP) IN THE ROSACEAE

424

Arranz et al. 101-103 showed that apple and other Rosaceae crops including peach, nectarine, pear, and

425

quince contain many non- extractable polyphenols (NEPP). NEPP are a group of phenolic

426

compounds that cannot be extracted using organic solvents or conventional analytical procedures but

427

require acid hydrolysis of the corresponding residues to release the compounds from the food matrix.

20


Page 21 of 63


428

NEPP are mostly hydrolyzable tannins, high molecular weight proanthocyanidins and phenolic acids

429

closely associated with dietary fiber and protein occurring in the food matrix. 101,104,105.

430

Non-extractable phenolic acids are insoluble and/or are associated with cell wall polysaccharides and

431

can include (depending on the food type) caffeic acid, p-coumaric acid, ferulic acid, o-, m-, and p-

432

hydroxybenzoic acid, sinapic acid, salicylic acid, syringic acid, and vanillic acid. 105 Although NEPP

433

are not detectable using conventional procedures, studies have reported their existence in fruits and

434

plant based foods including the Rosaceae. 102,104 NEPP as dietary polyphenols are not released for

435

digestion in the intestines by mastication, stomach pH and enzymatic activity, rather, they pass intact

436

into the colon for possible fermentation by colonic microflora.104 Arranz et al. 102 reported a huge gap

437

in the content of NEPP and extractable polyphenols (EPP) in the Rosaceae (Table 1). The study

438

showed EPP content of ~18.8-28 mg/100 g in methanol/acetone/water extracts of fresh apple, peach

439

and nectarine in comparison to NEPP of ~112-126 mg/100 g of acidic hydrolysates of the extraction

440

residue from the fruit, indicating that more than 80% of total phenolic compounds are left behind with

441

conventional extraction techniques. As a specific example, apple gallic acid content was determined

442

at ~2.9 mg/100 g NEPP and ~0.53 mg/100 g EPP, such that almost 85% of the total of this particular

443

phenolic acid required acid hydrolysis for chemical conversion to the analyte detected as gallic acid.

444

The NEPP determined in the study were mainly hydroxybenzoic and hydroxycinnamic acids.

445

Although NEPP are often disregarded in nutritional studies, they do contribute to the antioxidant

446

activity of polyphenols through a surface reaction in the small intestine. As observed in different

447

animal models, NEPP have been shown to increase antioxidant and antiproliferative capacities,

448

reduce intestinal tumorigenesis and modify gene expression. 104,105.

449 450

INFLUENCE OF STORAGE AND PROCESSING ON PHENOLICS 21



Page 22 of 63

451

Apple (Malus x domestica Mill.). Van der Sluis et al. 21 reported that the content of some flavonols

452

such as quercetin glycosides, phloridzin and anthocyanins in “Jonagold”, “Golden Delicious”, “Red

453

Delicious”, “Elstar”, and “Cox's Orange Pippin” were not affected by 52 weeks of storage in

454

controlled atmospheric conditions. The study also found that the concentration of chlorogenic acid

455

and total catechins decreased slightly in “Jonagold”, while the total catechin concentration decreased

456

slightly in “Golden Delicious” but the chlorogenic acid concentrations remained stable. Furthermore,

457

after 25 weeks of cold storage, there was no decrease in chlorogenic acid in any of the varieties while

458

catechins decreased slightly in “Golden Delicious”, “Elstar”, and “Cox's Orange Pippin”. The effects

459

of storage on apple peel phenolics by Golding et al. 106 confirmed that storage at 0 °C in air for up to

460

9 months has little effect on peel phenolic content. In further corroboration of the stability of apple

461

peel phenolic content, Lattanzio et al. 107 studied the collective action of phenolic compounds for

462

fungicidal properties in cold stored (2 °C) “Golden Delicious” apples and found no significant

463

decrease in phenolic concentration after 200 days. 108

464

Tokusoglu 108 reported variations in dihydrochalcone content among different apple varieties

465

after processing into juce. In a review of studies conducted on polyphenolic content of whole apple

466

compared to freshly-prepared and commercially-prepared juices, he reported a higher content and

467

concentration of hydroxycinnamic acids, procyanidins and anthocyanins in whole apple followed by

468

(in decreasing range of concentrations) fresh juice (cider apples), fresh juice (dessert apples), “clear”

469

commercial juice and “cloudy” commercial juice. Anthocyanins were found in red apple peel but

470

were not detected in the fresh or commercial juices tested. Chlorogenic acid, p-coumaroylquinic acid,

471

procyanidins B2, procyanidins C1, (-) epicatechin and (+) epicatechin were found in whole apple but

472

not in apple juice. In a review of apple components and their relationship to human health, Hyson et

473

al. 109 cites work reporting a wide range of total polyphenolic contents in whole apple, fresh juice and 22


Page 23 of 63


474

commercial juice. Depending on variety and growing conditions, total polyphenolic content ranged

475

from 5230–27,240 mg/kg in freeze-dried whole apple representing 67 cultivars, 154–970 mg/L in

476

fresh juice (with greater values typically representing juice prepared from cider apples) and 110–459

477

mg/L in commercial juices (with higher values found in ‘cloudy’ versus ‘clear’ juice preparations). 109.

478

Sweet cherry and tart cherry (Prunus avium L. and P. cerasus L.). Processed and stored cherry

479

are available year-round as frozen, whole canned, juice concentrate, etc. During her investigation

480

into the changes in anthocyanins and polyphenolics during canning and canned storage of cherries,

481

Chaovanalikit

482

from the fruit into the syrup with minimal total loss. The proportions of cyanidin and pelargonidin

483

rutinosides slightly decreased while cyanidin and pelargonidin glucosides increased, perhaps due to

484

partial hydrolysis of rutinose to glucose. The same investigator also determined that

485

hydroxycinnamates and epicatechins were affected by storage and temperature, decreasing

486

significantly after 5 months’ storage at both 2 °C and 22 °C. The degradation of epicatechins was

487

found to increase significantly at 22 °C. Flavonol glycosides were more stable, with a slight increase

488

at 22 °C. Additionally, the anthocyanin and phenolic composition of fresh frozen “Bing” fruit stored

489

at -23 °C and -70 °C for 3 and 6 months, respectively, was compared. A 67% loss of total

490

anthocyanins was observed after 3 months storage at -23 °C, and an 88% loss after 6 months. At the

491

much lower temperature of -70 ºC, only 11% and 12% loss was observed after 3 and 6 months,

492

respectively.

493

sweet cherry after 4 months storage at -20 ºC.

494

Apricot (Prunus armeniaca L.). The influence of drying parameters on the phenolic compounds in

495

two apricot cultivars, Pelese and Cafona, using air temperatures of 55 °C and 75 °C was investigated

496

by Madrau et al.

40

40

determined that approximately half of the anthocyanins and phenolic acids leach

In corroboration, Polesello and Bonzini

111

110

observed 34-74% anthocyanin loss in

Relative to fresh fruit, total phenolic concentration experienced an across-the23



Page 24 of 63

497

board decrease. However, the study reported significantly more decrease in chlorogenic acid,

498

neochlorogenic acid and catechin at 55 °C than at 75 °C, which was attributed to attenuation of

499

polyphenoloxidase enzymatic activity at the higher temperature. Epicatechin and quercetin 3 O-

500

glucoside incurred greater loss at the higher temperature than the lower temperature. Processed and

501

unprocessed apricots share similar qualitative profiles but lower quantities of phenolic compounds

502

were found in the processed products.

503

Plum (Prunus domestica L.). Bioactive compounds in plum are degraded during drying, and this

504

affects anthocyanins in particular. The polyphenolic contents are degraded by half in commercial

505

prune compared to fresh plum.

506

were slowly degraded as a function of drying time.

507

anthocyanins in prune during the 1st month of storage. These authors also observed, in both fresh and

508

dried fruits, that changes in catechins, hydroxycinnamic acids, anthocyanins and flavonols were

509

affected by both processing parameters and cultivar. Drying destroyed the anthocyanin compounds

510

while there was a significant decrease in the flavonols generally.

511

Quince (Cydonia oblonga Miller). There are limited studies on the effect of storage and cultural

512

practices on bioactive compounds in quince.

513

concentrations of different phenolic compounds than commercial jams, with the exception of

514

procyanidins.

515

suggesting adulteration of commercial jam with pear.

516

Strawberry (Fragaria spp). In a study conducted by Amaro et al.115, the effects of cultivar choice

517

and storage conditions were investigated as they relate to the fate of anthocyanins in strawberry jams.

518

Homemade jam from two cultivars, stored at room temperature with and without exposure to light,

519

was analyzed for total anthocyanin content and antioxidant activity.

114

54

Hydroxycinnamic acids, (+)-catechin and quercetin-3-O-rutinoside 112

Piga et al.

113

reported the disappearance of

However, home made jellies showed lower

Arbutin was identified in commercial but not in the homemade quince jam,

24


Anthocyanin content and

Page 25 of 63


520

stability are critical for an attractive red color as well as antioxidant capacity. Although the two

521

cultivars chosen for this study had radically different anthocyanin profiles, total anthocyanin content

522

of each jam was similar immediately after preparation. However, after 15 days of storage “Camarosa”

523

jam maintained its anthocyanin content at approximately the 90% level, while that of “American 13”

524

dropped by about 67%. After 60 days, approximately 50% of “Camarosa” anthocyanins were

525

quantified while only about 14% of the “American 13” anthocyanins were still detected. For both

526

cultivars, jam stored in the dark fared just slightly better than jam stored with exposure to light.

527

Raspberry (Rubus spp). Zafrilla et al. 116 conducted a study on the effect of processing and storage

528

on the ellagic acid/derivatives and flavonoid content of raspberry jam. Ellagic acid glycosides and

529

flavonol glycosides were found to be little affected by thermal processing; however, the content of

530

free ellagic acid increased 2.5-fold after processing. Although a decrease in total flavonoids was

531

observed, evaluation of individual phenolics in the processed jam during six months of dark storage

532

at 20 °C showed that ellagic acid continued to increase during the first month of storage up to 45 mg/

533

kg, then decreased slightly during the remaining storage period to a steady concentration of 20-25

534

mg/kg. The authors note this increase in free ellagic acid could be due to its chemical release from

535

ellagitannins or through increased extractability afforded during processing. Quercetin glucoside

536

content decreased significantly during the first three months from ~66 mg/kg to ~40 mg/kg of fresh

537

weight, then became stable during the rest of the storage period.116 Häkkinen et al. 117 investigated the

538

influence of processing and storage on flavonol content of various berries and found that quercetin

539

was well preserved in frozen red raspberries during 9 months storage at -20 °C while myricetin and

540

kaempferol were more susceptible to losses during storage.

541

Peach (Prunus persica L.). Asami et al. 118 investigated the impact of cold storage on total phenolics

542

(TP). Peach stored at 4 °C for a period of 14 days was measured for TP levels in peeled and unpeeled 25



Page 26 of 63

543

fruit on days 0, 7 and 14. The study showed that cold storage for 14 days resulted in no loss of TP

544

activity in either the peeled or the unpeeled fruit compared to fresh peach. However, a small increase

545

(p

Phenolic Compounds in Rosaceae Fruit and Nut Crops - Journal of

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