Influence of domestic processing and storage on flavonol contents in berries

Effects of domestic processing and storage on the flavonols quercetin, myricetin, and kaempferol in five berries were studied using an optimized RP-HPLC method with UV and diode array detection after an acid hydrolysis of the corresponding glycosides. In fresh berries, the total content of flavonols was highest in lingonberry (169 mg/kg) and black currant (157 mg/kg), intermediate in bilberry (41 mg/kg) and strawberry (17 mg/kg), and lowest in red raspberry (9.5 mg/kg). Cooking strawberries with sugar to make jam resulted in minor losses (quercetin 15%, kaempferol 18%). During cooking of bilberries with water and sugar to make soup, 40% of quercetin was lost. Traditional preservation of crushed lingonberries in their own juice caused a considerable (40%) loss of quercetin. Only 15% of quercetin and 30% of myricetin present in unprocessed berries were retained in juices made by common domestic methods (steam-extracted black currant juice, unpasteurized lingonberry juice). Cold-pressing was superior to steam-extraction in extracting flavonols from black currants. During 9 months of storage at 20 C, quercetin content decreased markedly (40%) in bilberries and lingonberries, but not in black currants or red raspberries. Myricetin and kaempferol were more susceptible than quercetin to losses during storage.     

Assessment of the differences in the phenolic composition of five strawberry cultivars (Fragaria x ananassa Duch.) grown in two different soilless systems

The phenolics from different strawberry cultivars (Aromas, Camarosa, Diamante, Medina, and Ventana) cultivated in two different soilless systems (with and without recycling nutrient solution) were quantified to assess differences in their profiles as a function of both the variety and the cultivation system. Considering groups of phenols, it was found that either anthocyanins (including pelargonidin-3-glucoside, cyanidin-3-glucoside, pelargonidin-3-rutinoside, pelargonidin-3-acetylglucoside, and two unidentified pelargonidin derivatives) or phenolic acids (including caffeic, ferulic, p-coumaric, p-hydroxybenzoic, and ellagic acid) were quantitatively more important than those of flavonols (quercetin and kaempferol); the ranges of values were 78.81-198.88, 49.77-128.37, and 12.85-43.04 microg/g, respectively. Considering individual compounds and after applying relevant pattern recognition techniques, it was concluded that the contents of cyanidin-3-glucoside, pelargonidin-3-rutinoside, p-coumaric acid, and pelargonidin-3-glucoside were the most appropriate variables to discriminate among varieties, whereas those of p-hydroxybenzoic acid and pelargonidin-derivative 1 were the most appropriate to discriminate between cultivation systems. The first factor of PCA was mainly linked to anthocyanins and quercetin, whereas the second principal component (PC) was related to kaempferol and p-coumaric acid.     

Phytochemical composition of onion during long-term storage

Onion cultivar “Sunpower” has growing popularity in Korea due to high storability. The present study considers changes in flavonols, sugars, and two amino acids in onion bulbs during a long-term storage in the ambient dark storage room and in glasshouse equipped with a climate control system. Flavonol and sugar contents were found to fluctuate noticeably during the storage period. Amino acid content remained relatively unchanged till the onset of inner sprouting, increasing afterward. Visible sprouts appeared at week 22 in the dark storage room and for four weeks later in the glasshouse. The bulbs lost 20–30% of their weight depending on storage conditions at the end of the storage trials. At the same time, the content of nutraceutics in study expressed on the dry weight basis remained of the same order of magnitude. The nature of observed variations in chemical composition of onions as well as relation of this phenomenon to physiological development of stored onion bulbs is discussed. A conclusion is made that the “Sunpower” onion cannot sustain overwinter storage.     

Ozonated water extends the shelf life of fresh-cut lettuce

The use of ozonated water as a sanitizer to extend the shelf life of fresh-cut lettuce and the effect on the antioxidant constituents (polyphenols and vitamin C) were investigated. Fresh-cut iceberg lettuce (Lactuca sativa L.) was washed at 4 degrees C using three different ozonated water dips [10, 20, and 10 activated by ultraviolet C (UV-C) light mg L(-1) min total ozone dose], and the dips were compared with water and chlorine rinses. Treated lettuce was packaged in air or active modified atmosphere packaging (MAP) (4 kPa of O2 + 12 kPa of CO2 balanced with N2) and stored for 13 days at 4 degrees C. Despite its strong oxidizing activity, ozonated water did not stimulate the respiratory activity of fresh-cut lettuce. Moreover, ozonated water maintained the initial visual appearance of fresh-cut lettuce and controlled browning during storage in air. Initially, ozonated water and chlorine reduced the total mesophilic population by 1.6 and 2.1 log, respectively, when compared with water. Active MAP was effective in controlling total microbial growth, achieving 2.0 log reduction in relation to samples stored in air at the end of storage. On the other hand, active MAP caused a 2.0-3.5 reduction of coliforms on sanitized samples compared with water-washed samples. The most efficient treatments were ozone 20 and ozone 10 activated by UV-C, which were as effective as chlorine. Changes in individual phenolic compounds were independent of the washing treatments. In air, chlorogenic and isochlorogenic acid contents increased noticeably after 13 days while monocaffeoyltartaric and dicaffeoyltartaric acids remained unchanged. MAP effectively suppressed accumulation of caffeoylquinic derivatives, whereas caffeoyltartaric derivatives decreased during MAP storage to reach similar levels. The content of vitamin C (ascorbic acid and dehydroascorbic acid) decreased during storage, particularly under MAP. Ozonated water could be an alternative sanitizer to chlorine for fresh-cut lettuce due to good retention of sensorial quality and browning control with no detrimental reduction in the antioxidant constituents.     

Characterization and quantitation of phenolic compounds in new apricot (Prunus armeniaca L.) varieties

Thirty-seven apricot varieties, including four new releases (Rojo Pasión, Murciana, Selene, and Dorada) obtained from different crosses between apricot varieties and three traditional Spanish cultivars (Currot, Mauricio, and Búlida), were separated according to flesh color into four groups: white, yellow, light orange, and orange (mean hue angles in flesh were 88.1, 85.0, 77.6, and 72.4, respectively). Four phenolic compound groups, procyanidins, hydroxycinnamic acid derivatives, flavonols, and anthocyanins, were identified by HPLC-MS/MS and individually quantified using HPLC-DAD. Chlorogenic and neochlorogenic acids, procyanidins B1, B2, and B4, and some procyanidin trimers, quercetin 3-rutinoside, kaempferol 3-rhamnosyl-hexoside and quercetin 3-acetyl-hexoside, cyanidin 3-rutinoside, and 3-glucoside, were detected and quantified in the skin and flesh of the different cultivars. The total phenolics content, quantified as the addition of the individual compounds quantified by HPLC, ranged between 32.6 and 160.0 mg 100 g(-1) of edible tissue. No correlation between the flesh color and the phenolic content of the different cultivars was observed.     

Phenolic composition of kiwifruit juice

Phenolic compounds in kiwifruit pulp were separated and characterized by reversed-phase HPLC, and the effect of juice processing on the phenolic composition was studied. Fractionation of phenolic compounds was achieved through selective elution from C-18 cartridges prior to preconcentration and subsequent separation by HPLC. Strongly acidic compounds were identified as derivatives of coumaric and caffeic acids, including chlorogenic acid, protocatechuic acid, and a derivative of 3,4-dihydroxybenzoic acid. The weakly acidic fraction contained epicatechin, catechin, and procyanidins (B3, B2, or B4 and oligomers). Flavonols were present as the glycosides of quercetin (glucoside, rhamnoside, and rutinoside) and kaempferol (rhamnoside and rutinoside). Phenolic compounds were present, at levels of <1-7 mg/L, in clarified juice. The concentration of phenolics was highest after high-temperature short-time treatment (HTST) of juice. Hydrolysis of hydroxycinnamic acids occurred after enzyme addition and HTST treatment. The flavonol glycoside composition is the best identifier of kiwifruit juice.     

贮藏温度对三疣梭子蟹蟹肉风味的影响

为延缓三疣梭子蟹品质劣变,延长其货架期,本试验研究了冰温贮藏、冷藏、冰藏对蟹肉挥发性风味、腺苷三磷酸(ATP)关联物及游离氨基酸含量的影响,并对其呈味物滋味强度值(TAV)及味精当量(EUC)进行分析。结果表明,冰温组蟹肉挥发性风味在贮藏前6 d 无明显变化,而冷藏和冰藏组蟹肉挥发性风味分别在贮藏第2和第4 天开始出现明显变化。冰温组蟹肉肌苷酸(IMP)和腺苷酸(AMP)的滋味强度值、游离氨基酸总量、鲜味氨基酸、甜味氨基酸和甜苦味氨基酸占总游离氨基酸的百分比、EUC均高于同期冰藏、冷藏。组综上所述,冰温贮藏能有效保持蟹肉良好风味,缓解蟹肉风味劣变。本研究结果为冰温贮藏技术在梭子蟹保鲜中的应用提供了一定的理论依据。     

Characterization and quantification of anthocyanins and polyphenolics in bluehHoneysuckle (Lonicera caerulea L.)

Anthocyanins and phenolics of 10 blue honeysuckle (Lonicera caerulea L.) genotypes were characterized and quantified by HPLC-DAD. Peak assignments were confirmed by low-resolution electrospray mass spectrometry. Six anthocyanins were detected with the major peak identified as cyanidin 3-glucoside. Five additional anthocyanins were characterized as cyanidin 3,5-diglucoside, cyanidin 3-rutinoside, pelargonidin 3-glucoside, peonidin 3-glucoside, and peonidin 3-rutinoside. Four polyphenolics were identified as chlorogenic acid, neochlorogenic acid, quercetin 3-rutinoside, and quercetin 3-glucoside. Two additional unidentified phenolics were characterized as flavonol and hydroxycinnamic derivatives based on UV-vis spectra. Hydroxycinnamate levels ranged from 30.4 to 156.2 mg/100 g, whereas the flavonol content ranged from 12.6 to 32.8 mg/100 g. The L. caerulea subspecies boczkarnikovae contained the highest amounts of hydroxycinnamic derivatives and flavonols.     

Quince (Cydonia oblonga miller) fruit characterization using principal component analysis

This paper presents a large amount of data on the composition of quince fruit with regard to phenolic compounds, organic acids, and free amino acids. Subsequently, principal component analysis (PCA) is carried out to characterize this fruit. The main purposes of this study were (i) the clarification of the interactions among three factors-quince fruit part, geographical origin of the fruits, and harvesting year-and the phenolic, organic acid, and free amino acid profiles; (ii) the classification of the possible differences; and (iii) the possible correlation among the contents of phenolics, organic acids, and free amino acids in quince fruit. With these aims, quince pulp and peel from nine geographical origins of Portugal, harvested in three consecutive years, for a total of 48 samples, were studied. PCA was performed to assess the relationship among the different components of quince fruit phenolics, organic acids, and free amino acids. Phenolics determination was the most interesting. The difference between pulp and peel phenolic profiles was more apparent during PCA. Two PCs accounted for 81.29% of the total variability, PC1 (74.14%) and PC2 (7.15%). PC1 described the difference between the contents of caffeoylquinic acids (3-O-, 4-O-, and 5-O-caffeoylquinic acids and 3,5-O-dicaffeoylquinic acid) and flavonoids (quercetin 3-galactoside, rutin, kaempferol glycoside, kaempferol 3-glucoside, kaempferol 3-rutinoside, quercetin glycosides acylated with p-coumaric acid, and kaempferol glycosides acylated with p-coumaric acid). PC2 related the content of 4-O-caffeoylquinic acid with the contents of 5-O-caffeoylquinic and 3,5-O-dicaffeoylquinic acids. PCA of phenolic compounds enables a clear distinction between the two parts of the fruit. The data presented herein may serve as a database for the detection of adulteration in quince derivatives.     

Solid foodstuff supplemented with phenolics from grape: antioxidant properties and correlation with phenolic profiles

Osmotic dehydration was assessed as an operation for supplementing a solid foodstuff (a gel was used as the model food) with grape phenolics from a concentrated red grape must to increase its antioxidant properties. The model food was processed for up to 24 h, and the osmotic pressure was adjusted by diluting the concentrated red grape must. In all conditions tested, low molecular weight phenolics (相似文献   

Characterization of cyanidin- and quercetin-derived flavonoids and other phenolics in mature saskatoon fruits (Amelanchier alnifolia Nutt.)

In order to further characterize the anthocyanins, flavonols, and other phenolics present in mature saskatoon ( Amelanchier alnifolia Nutt.) fruit, extracts were characterized using high-performance liquid chromatography, gas chromatography, and liquid chromatography-mass spectrometry. Cyanidin 3-O-galactoside, cyanidin 3-O-glucoside, cyanidin 3-O-arabinoside, and cyanidin 3-O-xyloside were identified as the four major anthocyanins in the mature fruit. The quercetin-derived flavonols, quercetin 3-O-glucoside, quercetin 3-O-galactoside, quercetin 3-O-arabinoside, quercetin 3-O-xyloside, quercetin 3-O-arabinoglucoside, quercetin 3-O-robinobioside, and quercetin 3-O-rutinoside were also identified in mature fruit extracts. In addition, two chlorogenic acid isomers (hydroxycinnamates), 3-O-caffeoylquinic acid and 5-O-caffeoylquinic acid were detected. The total content of the anthocyanin-, flavonol-, and hydroxycinnamate-type phenolics detected in mature 'Smoky' saskatoon fruit was 140, 25, and 96 mg/100 g fresh weight, respectively. These data further our knowledge of the phenolic composition of mature saskatoon fruit, and as anthocyanins, flavonols, and hydroxycinnamates exhibit antioxidant activities, the presence and levels of these classes of phenolics will aid in the understanding of the potential health-beneficial effects of saskatoon fruits in the human diet.     

Effect of brining on biological activity of leaves of Vitis vinifera L. (Cv. Sultani Cekirdeksiz) from Turkey

Leaves of Vitis vinifera (Fam. Vitaceae) cv. 'Sultani Cekirdeksiz' cultivated in Manisa-Alasehir in western Turkey, were processed with or without brine. Fresh, brined, and nonbrined leaves (after being subjected to 3 months of fermentation) were sampled and extracted with distilled water under reflux. Antioxidant, anti-inflammatory, and anti-nociceptive activities of the water extracts were investigated using in vitro and in vivo methods. Free radical scavenging activity (1,1-diphenyl-2-picrylhydrazyl, DPPH* assay), iron(III) reductive activity (reducing power activity assay), capacity of inhibition of linoleic acid peroxidation (ferric thiocyanate and thiobarbituric acid method), anti-nociceptive activity (p-benzoquinone-induced abdominal constriction test), and anti-inflammatory activity (carrageenan-induced hind paw edema model) were used to determine biological activities of the extracts. In addition, the contents of total phenolics, flavonoids, and flavonols in the extracts were determined by spectrophotometrical methods. Results were compared with those of ascorbic acid, butylated hydroxytoluene, and gallic acid as reference antioxidants. The extracts of fresh, brined, and nonbrined leaves showed almost the same activity in all antioxidant assays. These extracts inhibited the oxidation of linoleic acid to the same extent as BHT. Compositions of the extracts were analyzed by a reverse phase HPLC-PDA method. The occurrence of hydroxycinnamic acids (e.g., caffeic acid) and flavonoids (e.g., quercetin) was verified in the extracts. The content of total flavonoids as well as quercetin was increased by fermentation.     

Cultural system affects fruit quality and antioxidant capacity in strawberries

Cultural system [hill plasticulture (HC) versus matted row (MR)] and genotype interactions affected strawberry fruit quality. In general, fruit soluble solids content, total sugar, fructose, glucose, ascorbic acid, titratable acid, and citric acid contents were increased in the HC system. Fruit from HC also had higher flavonoid contents and antioxidant capacities. Strawberry fruit contains flavonols as well as other phenolic compounds such as anthocyanins and phenolic acids. Pelargonidin-based anthocyanins such as pelargonidin 3-glucoside, pelargonidin 3-rutinoside, and pelargonidin 3-glucoside-succinate were the predominant anthocyanins in strawberry fruit. The content of cyanidin-based anthocyanins, cyanidin 3-glucoside and cyanidin 3-glucoside-succinate, was much lower than that of pelargonidin-based anthocyanins in either system. Strawberry fruit from the HC system had significantly higher amounts of p-coumaroylglucose, dihydroflavonol, quercetin 3-glucoside, quercetin 3-glucuronide, kaempferol 3-glucoside, kaempferol 3-glucuronide, cyanidin 3-glucoside, pelargonidin 3-glucoside, pelargonidin 3-rutinoside, cyanidin 3-glucoside-succinate, and pelargonidin 3-glucoside-succinate. Fruits from plants grown in the MR system generally had the lowest contents of phenolic acids, flavonols, and anthocyanins. Strawberry fruit grown under HC conditions had significantly higher peroxyl radicals (ROO*) absorbance capacity (ORAC).     

Onions: a source of unique dietary flavonoids

Onion bulbs (Allium cepa L.) are among the richest sources of dietary flavonoids and contribute to a large extent to the overall intake of flavonoids. This review includes a compilation of the existing qualitative and quantitative information about flavonoids reported to occur in onion bulbs, including NMR spectroscopic evidence used for structural characterization. In addition, a summary is given to index onion cultivars according to their content of flavonoids measured as quercetin. Only compounds belonging to the flavonols, the anthocyanins, and the dihydroflavonols have been reported to occur in onion bulbs. Yellow onions contain 270-1187 mg of flavonols per kilogram of fresh weight (FW), whereas red onions contain 415-1917 mg of flavonols per kilogram of FW. Flavonols are the predominant pigments of onions. At least 25 different flavonols have been characterized, and quercetin derivatives are the most important ones in all onion cultivars. Their glycosyl moieties are almost exclusively glucose, which is mainly attached to the 4', 3, and/or 7-positions of the aglycones. Quercetin 4'-glucoside and quercetin 3,4'-diglucoside are in most cases reported as the main flavonols in recent literature. Analogous derivatives of kaempferol and isorhamnetin have been identified as minor pigments. Recent reports indicate that the outer dry layers of onion bulbs contain oligomeric structures of quercetin in addition to condensation products of quercetin and protocatechuic acid. The anthocyanins of red onions are mainly cyanidin glucosides acylated with malonic acid or nonacylated. Some of these pigments facilitate unique structural features like 4'-glycosylation and unusual substitution patterns of sugar moieties. Altogether at least 25 different anthocyanins have been reported from red onions, including two novel 5-carboxypyranocyanidin-derivatives. The quantitative content of anthocyanins in some red onion cultivars has been reported to be approximately 10% of the total flavonoid content or 39-240 mg kg (-1) FW. The dihydroflavonol taxifolin and its 3-, 7-, and 4'-glucosides have been identified in onions. Although the structural diversity of dihydroflavonols characterized from onions is restricted compared with the wide structural assortment of flavonols and anthocyanins identified, they may occur at high concentrations in some cultivars. From bulbs of the cultivar "Tropea", 5.9 mg of taxifolin 7-glucoside and 98.1 mg of taxifolin have been isolated per kilogram of FW.     

Changes in phenolic content of tomato products during storage

The effect of storage on the total polyphenol content and individual phenolic compounds as well as on the hydrophilic antioxidant capacity of ketchups and tomato juices was studied. The total polyphenol content was determined using the Folin-Ciocalteu assay, and the antioxidant capacity of the hydrophilic fraction was determined using DPPH and ABTS(+) assays. Individual polyphenols were identified and quantified using liquid chromatography/electrospray ionization tandem mass spectrometry on a triple quadrupole. All analyses were carried out for ketchups and tomato juices after storage for 3, 6, and 9 months. The total polyphenol content and antioxidant capacity of the hydrophilic fraction decreased during storage of ketchups and tomato juices. Ketchups, in general, showed a slightly greater stability during storage than tomato juices. The most significant decrease was observed for quercetin followed by caffeic and ferulic acids, whereas glycosilated polyphenols showed greater stability during storage.     

Effect of copigments and grape cultivar on the color of red wines fermented after the addition of copigments

The prefermentation addition of copigments led to significantly different red wines according to the copigment structure (flavonol or hydroxycinnamic acid) and the grape cultivar [Tempranillo (= Cencibel) or Cabernet Sauvignon]. The flavonol rutin enhanced copigmentation and anthocyanin extraction, improving the red color, but the hydroxycinnamic acids (especially caffeic acid) had converse results. The above effects were higher in Cabernet Sauvignon wines, particularly if rutin or p-coumaric acid was used. These wines showed the highest copigmentation as they contained more anthocyanins and flavonols, whereas the coumaroylated anthocyanins of Tempranillo wines could have prevented the action of the added copigments. After 21 months, the main pyranoanthocyanins found were the malvidin-3-glucoside 4-vinylphenol and the malvidin-3-glucoside 4-vinylcatechol (pinotin A) adducts. The results suggested that the former adduct was primarily generated following enzymatic decarboxylation of p-coumaric acid during fermentation, whereas pinotin A was formed through a pure chemical reaction, which depended on the concentration of free caffeic acid during aging.     

Oxidation of quercetin by salivary components. Quercetin-dependent reduction of salivary nitrite under acidic conditions producing nitric oxide

Under acidic conditions, nitrite is protonated to nitrous acid (pK(a) = 3.2-3.4) that can be transformed into nitric oxide by self-decomposition and reduction. When sodium nitrite was mixed with quercetin at pH 1-2, quercetin was oxidized producing nitric oxide. In addition to quercetin, kaempferol and quercetin 4'-glucoside were also oxidized by nitrous acid, but oxidation of apigenin, luteolin, and rutin was slow compared to oxidation of the above flavonols. These results suggested that flavonols, which have a free hydroxyl group at carbon position 3, can readily reduce nitrous acid to nitric oxide. When the pH of saliva was decreased to 1-2, formation of nitric oxide was observed. The nitric oxide formation was enhanced by quercetin, and during this process quercetin was oxidized. These results indicate that there is a possibility of reactions between phenolics and nitrous acid derived from salivary nitrite in the stomach.     

Flavanol and flavonol contents of cocoa powder products: influence of the manufacturing process

Major brands of cocoa powder products present in the Spanish market were analyzed for monomeric flavanols [(+)-catechin and (-)-epicatechin] and flavonols [quercetin-3-glucuronide, quercetin-3-glucoside (isoquercitrin), quercetin-3-arabinoside, and quercetin]. In addition, the influence of the manufacturing process of cocoa powder products, in particular, the alkalinization treatment ( Dutching), on the original content of these flavonoids has been studied. (-)-Epicatechin was in the range of 116.02-730.26 microg/g, whereas (+)-catechin was in the range of 81.40-447.62 microg/g in the commercial cocoa products studied. Among flavonols, quercetin-3-arabinoside and isoquercitrin were the major flavonols in the cocoa powder products studied, ranging from 2.10 to 40.33 microg/g and from 3.97 to 42.74 microg/g, respectively, followed by quercetin-3-glucuronide (0.13-9.88 microg/g) and quercetin aglycone (0.28-3.25 microg/g). To our knowledge, these results are the first quantitative data in relation to the content of individualized flavonol derivatives in commercial cocoa powder products. The alkalinization treatment resulted in 60% loss of the mean total flavonoid content. Among flavanols, (-)-epicatechin presented a larger decline (67%, as a mean percentage difference) than (+)-catechin (38%), probably because of its epimerization into (-)-catechin, a less bioavailable form of catechin. A decline was also confirmed for di-, tri-, and tetrameric procyanidins. In the case of flavonols, quercetin presented the highest loss (86%), whereas quercetin-3-glucuronide, quercetin-3-arabinoside, and isoquercitrin showed a similar decrease (58, 62, and 61%, respectively). It is concluded that the large decrease found in the flavonoid content of natural cocoa powder, together with the observed change in the monomeric flavanol profile that results from the alkalinization treatment, could affect the antioxidant properties and the polyphenol biovailability of cocoa powder products.     

Influence of storage upon light-induced chlorogenic acid accumulation in potato tubers (Solanum tuberosum L.)

The influence of 2 weeks and 3 months of dark storage upon light-induced chlorogenic acid accumulation within tuber tissue of four potato cultivars and upon 5-, 4-, and 3-caffeoylquinic acid concentrations within cv. King Edward was determined. Storage period significantly affected (P < 0.05) the magnitude of the light-induced chlorogenic acid response with accumulation rates 3-4 times higher in tubers exposed to light after 2 weeks compared with those placed under light after 3 months. Comparison of chlorogenic acid concentrations in controls after 2 and 3 months of dark storage indicated that tuber chlorogenic concentrations decline during prolonged cold store at 5 degrees C. Rates of accumulation in response to light were cultivar-dependent with cv. Fianna the most light-sensitive and cv. Maris Piper relatively light-insensitive. In virtually all cases exposure to sodium and fluorescent light promoted higher rates of accumulation than did exposure to high-pressure mercury light sources. Chlorogenic acid values steadily increased over 15 days of illumination with, in the majority of cases, no indication of cessation. Light exposure increased 5-, 4-, and 3-caffeoylquinic acid accumulation rates in cv. King Edward. Irrespective of storage period and light source, ratios of 5-:4-:3-caffeoylquinic acid were ca. 85:15:0 at day 0 and 52:42:6 by day 15.     

Changes in free amino acids and sugars in potatoes due to sulfate fertilization and the effect on acrylamide formation

To examine how sulfur deprivation may affect acrylamide formation in cooked potatoes, three varieties of potato were grown under conditions of either severe sulfur deprivation or an adequate supply of sulfur. In all three varieties sulfur deprivation led to a decrease in acrylamide formation, even though the levels of sugars, which are acrylamide precursors, were higher in tubers of the sulfur-deprived plants. In one variety the concentration of free asparagine, the other precursor for acrylamide, was also higher. There was a very close correlation between the concentration of asparagine in the tubers expressed as a proportion of the total free amino acid pool and the formation of acrylamide upon cooking, whereas sugars were poorly correlated with acrylamide. In potatoes, where concentrations of sugars are usually limiting, competition between asparagine and other amino acids participating in the Maillard reaction may be a key determinant of the amount of acrylamide that is formed during processing.