Saskatoon Fruit Research Articles

Effect of Ozone-Treated or Untreated Saskatoon Fruits (Amelanchier alnifolia Nutt.) Applied as an Additive on the Quality and Antioxidant Activity of Fruit Beers

Fruit of Saskatoon (Amelanchier alnifolia Nutt.) are a good source of bioactive compounds, such as polyphenols, including anthocyanins, as well as vitamins, macro- and microelements and fibre. By treating Saskatoon fruits with gaseous ozone, and adding the material as an enhancer to barley beers, it is possible to impact the contents of bioactive compounds in the produced fruit beers. Sensory tests showed that beers made from barley with addition of Saskatoon fruit of the ‘Smoky’ cultivar were characterised by the most balanced taste and aroma. Physicochemical analyses of fruit beers, produced with Saskatoon fruit pulp added on the seventh day of fermentation, showed that the beers enhanced with ozone-treated and untreated ‘Smoky’ Saskatoon fruits had the highest contents of alcohol, 5.51% v/v and 5.66% v/v, respectively, as well as total polyphenol contents of 395 mg GAE/L and 401 mg GAE/L, respectively, and higher antioxidant activity (assessed using DPPH•, FRAP and ABTS+• assays). It was demonstrated that the ozonation process led to a decrease in the contents of neochlorogenic acid, on average by 91.00%, and of caffeic acid by 20.62%, relative to the beers enhanced with ‘Smoky’ Saskatoon fruits not subjected to ozone treatment. The present study shows that Saskatoon fruits can be used in the production of beer, and the Canadian cultivar ‘Smoky’ is recommended for this purpose.

Developmental profile of anthocyanin, flavonol, and proanthocyanidin type, content, and localization in saskatoon fruits (Amelanchier alnifolia Nutt.).

Saskatoons (Amelanchier alnifolia Nutt.) are small fruits that contain substantial quantities of flavonoids. To further characterize and understand the role of these flavonoids during fruit development, anthocyanins, flavonols, and proanthocyanidins were identified, quantified, and localized over development in cultivars that produce blue-purple or white fruit at maturity. Anthocyanin content was low in young fruit and then dramatically increased as the fruit transitioned into ripening only in the pigmented-fruit (blue-purple) cultivars. Proanthocyanidins with both A-type and B-type linkages were detected in fruit, with (-)-epicatechin as the most abundant proanthocyanidin subunit. Flavonol and proanthocyanidin content was high in, and localized throughout, the tissues of young fruit and in the developing seed coats, with levels decreasing as the fruit expanded. Our data show that flavonoid type, content, and tissue localization vary throughout development in saskatoon fruit. These data can be used to target specific fruit developmental stages and flavonoid classes for optimization of health-beneficial flavonoid content.

Characterization of Cyanidin- and Quercetin-Derived Flavonoids and Other Phenolics in Mature Saskatoon Fruits (Amelanchier alnifoliaNutt.)

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.

Anthocyanins and nutrient components of saskatoon fruits (Amelanchier alnifolia Nutt.)

The benefits of fruits and vegetables in human health have long been recognized. Part of the beneficial effects of these foods on human health has been purported to be due to various polyphenolic compounds that have radical scavenging and antioxidant activity. Saskatoon fruits (Amelanchier alnifolia Nutt.) are native to Western Canada and are an emerging North American fruit crop. The blue-purple coloration of mature saskatoon fruit, an important quality characteristic, is due to the presence of anthocyanins, which are a class of polyphenolic compounds that contribute to protection against human diseases. The objective o f this review is to summarize the research on anthocyanins, a potential nutraceutical, and other nutrient components in saskatoon fruits. In addition, management practices to increase anthocyanin content in the mature fruit are discussed. Key words: Amelanchier alnifolia, saskatoon, fruit quality, chemical composition, anthocyanins

The Effects of Ethephon on Saskatoon (Amelanchier alnifolia Nutt.) Fruit Ripening

Field experiments were conducted on two cultivars of saskatoon to test the effectiveness of ethephon in stimulating uniform fruit ripening without compromising fruit quality. Shrubs of cultivars Northline and Smoky were sprayed to runoff with ethephon (0, 250, 500, and 1000 mg·L-1 for `Northline'; 0, 500, and 1000 mg·L-1 for `Smoky') prior to fruit maturity. Fruit were harvested 4 to 8 days after treatment and sorted into ripeness categories by size, and the fully ripe fruit were evaluated for quality (surface color, firmness, mean fruit weight, soluble solids, and titratable acids). Ethephon significantly increased the percent ripe fruit per shrub (by up to 9.7%) in both cultivars, without a significant effect on fruit quality. At concentrations up to 1000 mg·L-1, ethephon may be an effective ripening agent for saskatoon fruit without reducing fruit quality. Although there were significant differences in yield from year to year for both cultivars because of their biennial-bearing habit, ethephon treatments did not significantly affect total yields.

Efficacy of low O2 and high CO2 atmospheres in maintaining the postharvest quality of saskatoon fruit (Amelanchier alnifolia Nutt.)

Changes in fruit quality of saskatoon (cvs. Pembina, Smoky, Northline, and Thiessen) stored under three O2 levels (2, 10, and 21%) factorially combined with two CO2 concentrations (0.035% and 5%) were assessed during 56 d of storage at 0.5 °C. The 5% CO2 atmosphere combined with 21 or 10% O2 was most effective at minimizing losses in fruit soluble solids, anthocyanins, firmness, and fresh weight. Fungal colonization of fruit after 8 wk of storage was eliminated in 5% CO2 at all O2 concentrations. Storage of fruit in 0.035% CO2 and 21 or 10% O2 resulted in the highest titratable acidity and lowest ethanol concentrations. Ethanol did not exceed 0.03% in fruit stored in any of the atmospheres. While changes in some of the quality characteristics of fruit during storage were cultivar dependent, differences among cultivars were small, and all four cultivars benefited from controlled atmosphere storage. Key words:Amelanchier alnifolia, saskatoon fruit, controlled atmosphere, postharvest quality

A comparison of preharvest and postharvest ethylene production and respiration rates of saskatoon (Amelanchier alnifolia Nutt.) fruit during development

Changes in respiration and ethylene production rates of nine maturity classes of saskatoon (Amelanchier alnifolia, Nutt.) fruit after harvest were compared with those of fruit maturing and ripening on the plant. During ripening on the plant, ethylene production increased on a whole-fruit and fresh-weight basis, while respiration increased substantially on a whole-fruit basis but remained constant on a fresh-weight basis. Fruit harvested at the greenish yellow to pink stages (maturity classes four and five, respectively) increased their ethylene production until 15-20 h after harvest, and this was coincident with ripening to maturity class seven and thus a color change to red. Ethylene production then declined over the next 15 h. Respiration rates of harvested immature, mature, and ripe fruits declined over 5 days, except for a relatively brief 8-12% rise starting 15-20 h after harvest. This brief increase in respiration was characteristic of fruit of all maturity classes, likely reflecting a wound response associated with harvest rather than a ripening-induced change in metabolism. Continuous treatment of attached or detached fruit with propylene or ethylene in an open airflow system did not induce an increase in respiration earlier, relative to control fruit. The respiratory response of saskatoon fruit during postharvest ripening was thus very different from that of fruit that ripened on the plant. Thus, the increase in respiration associated with ripening could only be demonstrated on a whole-fruit basis if fruit remained on the plant. Preharvest and postharvest changes in ethylene production during ripening also differed but were both consistent with climacteric ripening.Key words: Amelanchier alnifolia, ethylene, ripening, saskatoon fruit.

Regulation of ethylene production and ripening by saskatoon (Amelanchier alnifolia Nutt.) fruit

Changes in respiration and ethylene production were characterized during maturation and ripening of saskatoon (Amelanchier alnifolia Nutt.) fruit. On a per fruit basis, respiration and ethylene production increased 78 and 400%, respectively, as fruit ripened on the plant and trends were consistent with those for climacteric fruits. When estimated on a fresh and dry weight basis, increased rates of ethylene production were still apparent during ripening; however, respiration rate declined. Trends in respiration rates and endogenous ethylene levels of harvested fruit of nine maturity classes, from immature green (class one) to fully ripe and purple (class nine), were consistent with those of fruit growing on the plant. Tissue prints showed that ACC (1-aminocyclopropane-1-carboxylic acid) oxidase was distributed throughout the pericarp of fruit at all nine maturity stages and that the enzyme was most concentrated in the immature stages on a per fruit basis. On a protein basis, ACC oxidase increased progressively with development of cv. Smoky fruit but remained relatively constant over the nine maturity classes of cv. Northline fruit. In contrast, ACC oxidase levels were relatively low in cv. Pembina fruit over the first four maturity classes, increased substantially as fruits developed from class four to five, then remained constant as fruit ripened to maturity class nine. Treating immature harvested Pembina fruit (maturity classes one to three) with ACC effected a 28- to 108-fold increase in ethylene production, compared with an average of only 7-fold for ACC-treated fruit of maturity classes four through nine. Preharvest treatment of class-three fruit with ACC induced ripening to maturity class eight within 5 days, while untreated fruit required 15 days to reach class eight. Vacuum infiltrating class four fruit with alpha-aminooxyacetic acid (AOA) or aminoethoxyvinyl glycine (AVG) inhibited ethylene production and color development substantially. The inhibiting effect of AOA on ripening was eliminated when fruit were infiltrated with equimolar concentrations of AOA and ACC. Cobalt, an ACC oxidase inhibitor, also inhibited ethylene production and ripening. Collectively, our results indicate that ethylene synthesis by preclimacteric fruit is limited by the availability of ACC, ethylene is responsible for initiating ripening, and thus, saskatoon fruit are climacteric.Key words: Amelanchier alnifolia, saskatoon, fruit ripening, ethylene.

Effects of storage temperature and atmosphere on saskatoon (Amelanchier alnifolia Nutt.) fruit quality, respiration and ethylene production

Abstract Low temperature and controlled atmospheres (CA) were tested for their effectiveness in extending the storage life of saskatoon fruit. The quality of fully ripe (purple) `Smoky' and `Pembina' fruit was assessed over 40 days of storage at 0.5 or 4.0°C in humidified (95% RH) air. Fungal colonization, fruit softening, fresh-weight loss, and anthocyanin degradation were substantially lower in fruit stored at 0.5°C than in that stored at 4.0°C. `Smoky' fruit maintained higher soluble solids when stored at 0.5°C than at 4.0°C, but that of `Pembina' was not affected by temperature. Decreasing the O2 concentration from 23 to 5.8% had little effect on fruit respiration at 23°C; however, the respiration rate fell about 26% as the O2 concentration was lowered from 5.8 to 1.7%. A 2% O2 atmosphere was above the extinction point for aerobic respiration at 23°C. Fruit (cvs. `Smoky' and `Northline') of maturity classes seven, eight and nine were stored in 2, 10 or 21% O2 (0.035% CO2) at 4.0°C (95% RH), and respiration and ethylene evolution were monitored over 10 days. The rate of ethylene production by fruit of both cultivars decreased linearly with advancing maturity class and with declining O2 concentration. Furthermore, the increase in ethylene production rate of maturity class nine (fully ripe) fruit with increasing O2 concentration was less than that from fruit of maturity classes seven and eight. Respiration rates of `Northline' and `Smoky' fruit were equal at 21% O2, but `Northline' fruit had a 15% lower respiration rate than `Smoky' fruit at 2% O2. Collectively, our results show that storage at 0.5°C was more effective than 4.0°C at maintaining fresh quality of saskatoon fruit. Low O2 atmosphere (2%) effectively slowed ethylene production and fruit respiration and thus may be a beneficial adjunct to low-temperature storage.

Patterns of Saskatoon (Amelanchier alnifolia Nutt.) Fruit and Seed Growth

Saskatoon fruit are an emerging horticultural crop across the Canadian prairies. As fruit size varies greatly among cultivars, knowledge of fruit growth patterns and factors that affect fruit size can be used to establish breeding trials and develop orchard management strategies that could enhance the production of this crop. In this study, we 1) determined fruit and seed growth patterns among large-, medium-, and small-fruited cultivars of saskatoon using growing degree days to standardize time to crop development and 2) assessed the role of seed number on fruit size. Fruit growth patterns of four cultivars (Thiessen, Northline, Regent, and Smoky) were determined from weekly measurements of fresh and dry fruit mass during two consecutive seasons. These growth patterns exhibited three phases. The largest fruit at maturity were from `Thiessen', followed by `Northline', `Smoky', and `Regent', in descending order. Pedicel cross-sectional areas 1 week before maturity correlated linearly with increasing fresh and dry fruit mass and seed number per fruit. At maturity, seed number per fruit correlated linearly with fresh and dry fruit mass. `Thiessen' contained significantly more seeds per fruit (4.6) than `Northline' (3.7), `Smoky' (3.2), and `Regent' (3.2). The results of this research suggest potential areas for orchard management improvement and future research directions for saskatoon crop improvement.

Physical and chemical changes during growth, maturation, and ripening of saskatoon (Amelanchier alnifolia) fruit

Both ongoing and future studies of saskatoon (Amelanchier alnifolia Nutt.) fruit would benefit from a maturity index that could be referred to as as an indicator of fruit development. Accordingly, two cultivars of saskatoon fruit (Northline and Smoky) were sorted subjectively into nine maturity and ripeness stages based on differences in size and color. The physicochemical attributes of each stage were then characterized in detail. Color ranged from mostly green (stages 1–4) to white–pink (5) to pink (6) to red (7–8) to purple (9). The fastest gains in fresh and dry weights occurred over the later stages of development (from stages 5 to 9), while increases in fruit diameter between stages 1 and 9 were linear. Fruit firmness declined substantially between the first and the fifth maturity stages and then only slightly as ripening progressed to maturity class 9. Fruit nitrogen concentration decreased throughout development as did pH, chlorophyll, and phenolics. Fruit soluble solids, the ratio of soluble solids to titratable acidity, and anthocyanins increased from the fourth to the ninth stage of development. Glucose and fructose concentrations were about equal, increased about eightfold from class 4 to 9, and along with sorbitol were the major carbohydrates in fruit. Starch was nondetectable in fruit at all stages. Succinate was the predominant organic acid in immature fruit; however, levels declined with advancing maturity, and malate was the most concentrated organic acid in mature fruit. Changes in the relative concentrations of quinate, galacturonate, citrate, pyruvate, cis-aconitate, fumarate, and oxalate were also characterized with advancing maturity. In total, the concentration of organic acids dropped at least twofold as fruits developed from class 1 to 3, then declined relatively slowly through the remaining developmental stages. Cultivar variability in physicochemical attributes was relatively small and insignificant with regard to sorting and classifying fruits according to maturity. It is proposed that this nine-point maturity index be adopted for future studies on saskatoon fruit growth and development. Key words: Amelanchier alnifolia, fruit, maturity class, ripening, organic acids, sugars.

Aliphatic components of the epicuticular wax of developing saskatoon (Amelanchier alnifolia) fruit

The epicuticular wax of saskatoon fruit (Amelanchier alnifolia Nutt. cv. Smoky) was analyzed at four stages of maturity. Total wax per unit surface area varied during fruit development, with a net decline from the youngest to the most ripe stage. Surface wax ultrastructure, as revealed by scanning electron microscopy, consisted of pinhead-like crystals that decreased with maturity and platelike crystals that increased with maturity. The major aliphatic compounds were alkanes (C23to C29), long chain esters (C36to C42), primary alcohols (C20to C30), and a secondary alcohol (C29). The esters were composed of primary alcohols (C20to C28) and saturated fatty acids (C16to C24). The most abundant wax components at all stages were nonacosan-10-ol and nonacosane. Keywords: serviceberry, saskatoon fruit, epicuticular wax, aliphatic chemistry, ultrastructure.

Fruit Development in Saskatoon (Amelanchier alnifolia Nutt.)

Saskatoon fruits, an emerging horticultural crop across the Canadian prairies, vary greatly in size among cultivars. In this study, we compare fruit development patterns among large, medium, and small fruited cultivars of saskatoon, and assess the role of seed number and pedicel diameter on fruit size. Fruit growth patterns of four cultivars (Thiessen, Northline, Regent, and Smoky) were determined from weekly measurements of fruit diameters and fresh and dry flower/fruit weights during two consecutive growing seasons. The developmental patterns of fruit growth determined using the above criteria were similar among cultivars and between years. At maturity, the largest fruits (fresh weight) obtained were from cv. Thiessen, followed by `Northline', `Smoky', and `Regent', in descending order. Pedicel diameters (one week prior to maturity) correlated linearly with increasing fruit diameter and fresh weight. At maturity, seed number per fruit correlated linearly with increasing fruit weight. Thiessen contained significantly more seeds per fruit (4.6) than `Northline' (3.7), `Smoky' (3.2), and `Regent' (3.2).

Using Ethephon to Stimulate Synchronous Ripening of Saskatoon Fruit

Ethephon was applied in two consecutive years to saskatoon (Amelanchier alnifolia Nutt.) shrubs (`Northline' and `Smoky') to determine its effects on synchronizing fruit ripening. Ripeness can be visually assessed by color (green = immature; red = mature, not ripe; purple = mature, fully ripe). Ethephon (applied when fruit were ≈ 70% red) at 250, 500, and 1000 ppm increased the percentage of ripe fruit obtained from `Northline' by 2%, 4%, and 6%, respectively. Due to pronounced seasonal yield differences for `Smoky', ethephon had no effect on the percentage of ripe fruit obtained in 1994. However, in 1995, ethephon (applied at 70% red fruit stage) at 500 and 1000 ppm increased the percentage of ripe fruit obtained from `Smoky' by 4% and 2%, respectively. Fruit quality, evaluated with respect to surface color development, flesh firmness, fruit size, soluble solids concentration, titratable acidity, and the soluble solids: titratable acids ratio, was not significantly affected by ethephon treatments. This work was supported in part by AARI-FFF grant no. 940442.

Ripening Physiology and Storability of Saskatoon Fruit

Saskatoon (Amleanchier alnifolia Nutt.) fruit were stored into nine maturity stages based on color and size. Fruit color ranged from green (stages 1–4) to pink (5 and 6) to red (7 and 8) to purple (9). Fruit diameter of `Smoky' increased linearly as maturity advanced from 1 to 9. Fresh weight increased by 46 mg/fruit for each stage between 1 and 6, and then increased by 141 mg/fruit for each stage between 7 and 9. Firmness declined linearly from maturity 1 to 5, then remained relatively constant through maturity 9. The ability of fruit of maturities 3, 5, and 7 to ripen after harvest was assessed over 6 days (23C). Color measurements of maturities 3 and 5 indicated a change from green to pink, but no further change to purple. Color of maturity 7 changed to equal that of fully ripe (purple) maturity 9 fruit. After 6 days, fruit firmness of maturities 5 and 7 was equal that of freshly harvested maturity 9 fruit; however, maturity 3 fruit were incapable of softening to the same degree as fully ripe fruit. While fruit harvested at stage 7 appear to ripen normally, a significant lower fruit fresh weight precludes harvesting at this stage. Internal C2H4 concentration of fruit, and production by fruit in an open air-flow system, were monitored for `Northline', maturities 1–9. Internal C2H4 concentration of maturity 6 fruit was about 8-fold higher than that of maturity 4 fruit. Moreover, C2H4 production rate of maturity 5 fruit increased 3-fold from 10 to 25 h after harvest and then fell, reached the initial rate by 45 h after harvest. The respiration of these fruits also increased (by ≈70%) from 15 to 30 h after harvest, and then declined. Fruit color had changed from mostly green to red by 45 h after harvest. Collectively, these results indicate that saskatoon fruit exhibit a climacteric ripening patter. Results on the efficacy of controlled-atmosphere and hypobaric storage to delay physiological and pathological deterioration of saskatoon fruits will be presented.