SEARCH

SEARCH BY CITATION

Keywords:

  • 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid);
  • ascorbic acid;
  • bioactive food;
  • polyphenols;
  • smoothies

Summary

  1. Top of page
  2. Summary
  3. Introduction
  4. Materials and methods
  5. Results and discussion
  6. Conclusions
  7. Acknowledgments
  8. References

The aim of this study was to determine the usability of fruits of selected species growing in Europe for the smoothies production. The organoleptic assessment, analysis of polyphenols and vitamin C content and antioxidant activity of products were determined. The panellists were most in favour of the smoothies containing cranberry, black currant and bilberry purees as well as juice from dog rose. Polymerised proanthocyanidins were found to predominate in most of the products, except for the black currant smoothies (B3) where the main group of polyphenols were anthocyanins. The content of proanthocyanidins was higher in the smoothies containing dog rose juice. The analysed products differed significantly in the content of vitamin C, as the highest content of ascorbic acid was determined in black currant smoothies with dog rose juice and bilberry puree (168.98 mg/100 g).


Introduction

  1. Top of page
  2. Summary
  3. Introduction
  4. Materials and methods
  5. Results and discussion
  6. Conclusions
  7. Acknowledgments
  8. References

Smoothies are mainly fruit-based products with a typical semi-liquid, smooth consistency that are prepared by mixing – in appropriate proportions – juice and fruits that were earlier ground to puree. Often, they are also produced with other additives, for example, milk, yoghurt or ice cream (Keenan et al., 2010). The market of these products is relatively young. The term ‘smoothies’ has appeared for the first time in the seventies in the United States of America and in the Great Britain (Qian, 2006). Owing to a low consumption of fruit and vegetables in these countries, a means has been searched for to diversify the assortment of processed food products and to encourage consumers to enrich their everyday diet if not in fresh fruit or vegetables, then at least in products made of then. Generally, smoothies are prepared from fresh, unprocessed fruits, but juices are added as well in order to impart them a drinking consistency and to profile the flavour of a finished product. Compared with juices that are the most popular form of fruit products consumption, smoothies are characterised by a higher energy value and higher contents of dietary fibre, vitamin C and other substances with antioxidative potential (Ruxton, 2008; Watzl, 2008). They are produced from popular fruits that are eagerly consumed all over the world including bananas, pineapples, mango, strawberries, oranges, kiwi, peaches or apples (Müller et al., 2010). The sale of ‘smoothies’-type products in the USA is estimated to reach over 2 billion USD annually, and their consumption – to increase by 80% within the last 5 years. In the Great Britain, the market of these products was estimated at 141 million pounds only in 2010. Despite availability of a whole range of raw materials and relatively simple production technology of smoothies, these products are still little known in Europe, particularly in Poland, Czech Republic, Slovakia or Russia. Although the market of fruit products is successively developing, they are still underpromoted. As indicated in a report of the British Soft Drinks Association (2011), the key factor that influences on the popularity of smoothies is their price.

In spite of the above, the potential of horticulture production, species diversity of raw materials and an increasing interest of consumers in functional foods become the mainstay of the sector of smoothies production in the food industry. Attractive sensory values of these products coupled with unlimited possibilities of diversifying their composition make smoothies an excellent alternative to traditional, well known to consumers' products, for example juices, nectars or pomace. The mixing of a few fruit species allows obtaining not only a sensory-attractive product but, most of all, with more beneficial health-promoting values. This may play a significant role in the processing of fruits poor in bioactive compounds. For instance, the content of polyphenols in clouded apple juices ranges from 8.57 to 104.44 mg/100 mL (Oszmiański et al., 2007; Jaros et al., 2008; Markowski et al., 2009). Significantly richer in this respect are juices from pome and berry fruits, including cherry (110.62 mg/100 mL), strawberry (130.21 mg/100 mL), cranberry (154.69 mg/100 mL), black currant (191.98 mg/100 mL) (Piljac- Zegarac et al., 2009), raspberry (123.42 mg/100 mL) or chokeberry juices (915.44 mg/100 mL) (Jakobek et al., 2007). However, there are sparse examples in literature that would report on beneficial effects of mixing jams and other fruit processed products on bioactive compounds content of such a mixed product (Auger et al., 2011; Wojdyło et al., 2013).

Amongst many species of cultivable and wild plants growing, for example, in eastern Europe, a high content of biologically active compounds is typical of: chokeberry, bilberry, black currant, cranberry, sea buckthorn, rose hips, quince and Japanese quince. This group may also include fruits of apple tree. Although they are not especially rich in health-promoting compounds, yet owing to their high consumption, they play a significant role in an everyday day of Fines, Dutchmen, Poles or Americans (Boyer & Liu, 2004).

The international promotion of the so-called super-fruits is focused, primarily, on little known plants with a limited range of occurrence – acerola (Malpighia pucinifolia L.), açaí (Euterpe oleracea Mart.), pomegranate (Punica granatum L.), great Morinda (Morinda citrifolia L.) or goji berries (Lycium barbarum L.). However, multiyear investigations conducted by European research centres show that also many popular species of fruits from a wider climatic zone, for example, chokeberry (Aronia melanocarpa (Michx.) Elliott), dog rose (Rosa canina L.), black currant (Ribes nigrum L.), Japanese quince (Chaenomeles japonica L.) and bilberry (Vaccinium myrtillus L.), display high, although insufficiently exploited, health-promoting potential. Promotion of these fruits could have a positive impact on the development of the global market of functional foods.

In view of the above, the aim of this study was to determine the usability of fruits of selected species of cultivable and wild plants for the production of smoothies with high contents of polyphenolic compounds and ascorbic acid.

Materials and methods

  1. Top of page
  2. Summary
  3. Introduction
  4. Materials and methods
  5. Results and discussion
  6. Conclusions
  7. Acknowledgments
  8. References

Reagents and chemicals

Quercetin- and keampferol-3-O-glucoside, cyanidin-3-rutinoside, p-coumaric acid, (+)-catechin, (−)-epicatechin were purchased from Extrasynthese (Lyon Nord, France). Chlorogenic acid and neochlorogenic acid were supplied by TRANS MIT GmbH (Giessen, Germany). Trolox (6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid), 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS); potassium persulfate, acetic acid, TPTZ (2,4,6-tripyridyl-1,3,5-triazine), FeCl3,, phloroglucinol, ascorbic acid, acetonitrile and methanol were purchased from Sigma-Aldrich (Steinheim, Germany).

Raw materials for the production of smoothies

Ripe fruits of apple variety ‘Champion’ (Malus domestica Borkh.), chokeberry variety ‘Galicjanka’ [Aronia melanocarpa (Michx.) Elliott], cranberry variety ‘Ben Lear’ (Vaccinium macrocarpon L.), black currant variety ‘Titania’ (Ribes nigrum L.) and bilberry (Vaccinium myrtillus L.) were purchased in retail in 2011. Dog rose (Rosa canina L.) and quince fruits (Cydonia oblonga Mill.) were obtained from the garden of medicinal plants, at the Medical University of Wrocław. Fruits of common sea buckthorn variety ‘Aromatnaya’ (Hippophae rhamnoides L.) and Japanese quince (Chaenomeles japonica L.) originated from the Institute of Horticulture in Skierniewice. Owing to a significant spread in harvest time of particular fruits (from June till October 2011), cleansed and washed fruits were frozen at a temperature of −20 °C, and stored in this form until smoothies production. Fruits of quince, Japanese quince and apples were kept in a cold store at a temperature of 4 °C up to 1 week since harvest.

Technology of smoothies production

The production process included three main technological stages. At stage I, juices were produced from fruits of apples, quince, chokeberry and black currant that constituted the basis of the end products. Stage II involved the processing of pome fruits (quince, Japanese quince) and berry fruits (chokeberry, cranberry, black currant, bilberry, sea buckthorn) into puree, and dog rose into juice. Stage III consisted in mixing both semi-products in proportions provided in a recipe (Table 1).

Table 1. Characteristic of smoothies samples
No.SymbolSmoothies compoundsNo.SymbolSmoothies compounds
  1. Compound codes: ApJ- apple juice, QJ- quince juice, ArJ- chokeberry juice, BcJ- black currant juice, QP- quince puree, SbP- sea buckthorn puree, RcP- dog rose puree, JqP- Japanese quince puree, BcP- black currant puree, CrP- cranberry puree, RcJ- dog rose juice, BbP- bilberry puree.

1A1ApJ 100 g + QP 25 g + SbP 25 g17C1ArJ 100 g + QP 25 g + SbP 25 g
2A1′ApJ 100 g + QP 40 g + SbP 10 g18C1′ArJ 100 g + QP 40 g + SbP 10 g
3A2ApJ 100 g + RcP 25 g + JqP 25 g19C2ArJ 100 g + RcP 25 g + JqP 25 g
4A2′ApJ 100 g + RcP 40 g + JqP 10 g20C2′ArJ 100 g + RcP 40 g + JqP 10 g
5A3ApJ 100 g + BcP 25 g + CrP 25 g21C3ArJ 100 g + BcP 25 g + CrP 25 g
6A3′ApJ 100 g + BcP 40 g + CrP 10 g22C3′ArJ 100 g ++ BcP 40 g + CrP 10 g
7A4ApJ 100 g + RcJ 25 g + BbP 25 g23C4ArJ 100 g + RcJ 25 g + BbP 25 g
8A4′ApJ 100 g + RcJ 40 g + BbP 10 g24C4′ArJ 100 g + RcJ 40 g + BbP 10 g
9Q1QJ 100 g + QP 25 g + SbP 25 g25B1BcJ 100 g + QP 25 g + SbP 25 g
10Q1′QJ 100 g + QP 40 g + SbP 10 g26B1′BcJ 100 g + QP 40 g + SbP 10 g
11Q2QJ 100 g + RcP 25 g + JqP 25 g27B2BcJ 100 g + RcP 25 g + JqP 25 g
12Q2′QJ 100 g + RcP 40 g + JqP 10 g28B2′BcJ 100 g + RcP 40 g + JqP 10 g
13Q3QJ 100 g + BcP 25 g + CrP 25 g29B3BcJ 100 g + BcP 25 g + CrP 25 g
14Q3′QJ 100 g + BcP 40 g + CrP 10 g30B3′BcJ 100 g + BcP 40 g + CrP 10 g
15Q4QJ 100 g + RcJ 25 g + BbP 25 g31B4BcJ 100 g + RcJ 25 g + BbP 25 g
16Q4′QJ 100 g + RcJ 40 g + BbP 10 g32B4′BcJ 100 g + RcJ 40 g + BbP 10 g

Production of juices – stage I

Washed and cut (with a knife) pieces of apples, quince fruits and chokeberry were disintegrated for 30 s in a Thermomix appliance (Vorwerk, Wuppertal, Germany). To prevent enzymatic browning of the fruits, a rhubarb juice in the amount of 25 g/kg of fruits was added to apple and quince pulp. In the case of bilberries, the pulp was heated (90 °C; Thermomix) to loosen fruits structure and to increase juice yield. Particular pulps were pressed in a basket press (Zodiak, SSRE, Poland), at a piston thrust of 5000 KG cm−2 for 2 min. The resultant juice was pasteurised in Thermomix, by heating to 100 °C for 6 min. Hot juice was poured into colourless 900-mL jars, left for pasteurisation (10 min) and cooled to 20 °C. Juices from black currant and dog rose were produced analogously; however due to a high content of pectins in the fruits, the pulp needed to be macerated with an enzymatic preparation before pressing. In the case of black currant, 0.5 g of PANZYM BE XXL enzyme (Begerow, Eaton Technologies GmbH, Langenlonsheim, Germany) per kg of fruits (50 °C, 1 h) was applied. Dog rose mash was depectinised for 2 h at a temperature of 50 °C with 5 g of the same enzyme per kg of fruits.

Production of puree – stage II

Washed and cut (with a knife) into pieces pome fruits, berry fruits and rose hips were ground and heated at a temp. of 90 °C for 30 s in a Thermomix appliance (Vorwerk). Next, the resultant pulp was passed through a sieve (2 mm) with the use of a food processor (Symbio; Zelmer, Rzeszow, Poland). The puree were closed in 900-mL jars and immediately cooled to 20 °C.

Production of smoothies – stage III

The semi-products in the form of juices and pomace, produced at stages I and II, were mixed in the following proportion: 100 g of base juice + 40 g of base fruit pomace or rose hip juice + 10 g of supplementing pomace (Table 1), and heated to a temperature of 100 °C in Thermomix. The hot product was poured into colourless 80-mL glass jars, left for pasteurisation (10 min) and afterwards cooled to T = 20 °C.

Experimental material

The experimental material included 32 samples of smoothies, produced in 4 variants: smoothies based on apple juice (variant A), quince juice (Q), chokeberry juice (C) and black currant juice (B) (Table 1).

Consumer evaluation of smoothies

The organoleptic assessment of smoothies was carried using a 9-degree hedonic scale with boundary indications: ‘I do not like very much’ (1) – ‘I like very much’ (9). The assessment included the following quality attributes: colour, taste, aroma, and consistency, and was conducted by a group of 30 trained panellists. Coded samples were provided to the panellists for the evaluation at a temperature of ca. 20 °C in transparent, uniform, 50-mL plastic containers. Analyses of smoothies were carried out within two consecutive days (day 1 – assessment of apple and quince smoothies, day 2 – assessment of chokeberry and black currant smoothies). Of the thirty-two analysed samples, eight products were selected that received the highest scores in the sensory assessment (two of each type of smoothies). The selected samples were determined for the contents of polyphenolic compounds and ascorbic with the HPLC method and for antioxidative activity with the ABTS method.

Determination of polyphenols by UPLC coupled to PDA and FL detector

The analysis of polyphenolic compounds and proanthocyanidins was carried out on a UPLC system Aquity (Waters, Milford, MA, USA) consisting of a binary solvent manager and sample manager and photodiode array detector (PDA, model λe) and fluorescence detector (FL). Empower three software was used for chromatographic data gathering and integration of chromatograms. A UPLC analyses were performed on a BEH Shield C18 analytical column (2.1 × 5 mm; 1.7 μm). The flow rate was 0.45 mL/min. A partial loop injection mode with a needle overfill was set up, enabling 5 μL injection volumes when 10 μL injection loop was used. Acetonitrile was used as a strong wash solvent and 10% acetonitrile as a weak wash solvent. All incubations were done in triplicate.

Analysis of polyphenols compounds

The solvent for analysis of polyphenols was prepared by described previously by Wojdyło et al. (2008). The analytical column was kept at 30 °C by column oven, sample manager at 4 °C. The mobile phase used for the separation was composed of aqueous formic acid 4.5% (A) and acetonitrile (B) in gradient mode set as follows: initial conditions 1% B; from 0 to 5 min 75% B; from 5.0 to 6.5 min 100% B; from 6.5 to 7.5 min the composition was kept constantly at 100% B; from 7.5 to 8.5 min reconditioning the column to initial gradient (1% B). The runs were monitored at the following wavelengths: flavan-3-ols at 280 nm, hydroxycinnamates at 320 nm and flavonol glycosides at 360 nm, and were measured over the wavelength range of 200–600 nm in steps of 2 nm. Retention times and spectra were compared with those of pure standards. Anthocyanin was expressed as cyanidin 3-O-rutinoside, quercetin derivatives and keampferol 3-O-galactoside was expressed as quercetin and keampferol 3-O-glucoside (respectively).

Analysis of proanthocyanidins by phloroglucinolysis method

Direct phloroglucinolysis was performed as described by Kennedy et al. (2001). Portions (0.05 g) of freeze-dried smoothies were precisely measured into 2-mL Eppendorf vials, then 0.8 mL of the methanolic solution of phloroglucinol (75 g/L) and ascorbic acid (15 g/L) were added. After addition of 0.4 mL of methanolic HCl (0.3 mol/L), the vials were closed and incubated for 30 min at 50 °C with vortexing all time by thermo Shaker (TS-100; BIOSAN, Riga, Latvia). The reaction was stopped by placing the vials in an ice bath and adding 0.6 mL of sodium acetate buffer (0.2 mol/L). Next, the vials were centrifuged immediately at 20 000 × g for 10 min at 4 °C. The analytical column was kept at 15 °C by column oven, sample at 4 °C. Mobil phase generated from 2.5% acetic acid (A) and acetonitrile (B) was mixed directly in the instrument. Solvents A and B were used in the following gradient: initial, 2% B; 0.6–2.17 min, 3% B; 2.17–3.22 min, 10% B; 3.22–5.00 min, 15% B and from 5.00 to 6.00 min followed by washing and reconditioning of the column (1.50 min). The calibration curves which were based on peak area were established using (+)-catechin, (−)-epicatechin, (+)-catechins and (−)-epicatechin–phloroglucinol adducts standards. The average degree of polymerisation was calculating the molar ratio of all the flavan-3-ol units (phloroglucinol adducts + terminal units) to (−)-epicatechin and (+)-catechin, which correspond to terminal units. For analysis excitation, wavelength of 278 nm and emission wavelength of 360 nm were used.

Analysis of antioxidant capacity

The solvent for analysis was prepared and described previously by Wojdyło et al. (2008). The ABTS°+ activity of sample was determined according to the method by Re et al. (1999). All determinations were performed in triplicates using a Shimadzu UV-2401 PC spectrophotometer (Shimadzu, Kyoto, Japan). The results of the assay were expressed relative to mmol Trolox/100 g.

Analysis of L-ascorbic acid content

The analysis of L-ascorbic acid was made according to the method described previously by Oszmiański & Wojdyło (2009). The fresh smoothies (3–4 g) were mixed with 50 mL of 0.1 m phosphoric acid and centrifuged at 14 000 g for 10 min 4 °C. The estimation of L-ascorbic acid was carried out on the Waters liquid chromatography with a tunable absorbance detector (Waters 486) and quaternary pump with Waters 600 Controller apparatus (Waters Associates). A 20 μL sample was injected into a Chromolith Performance RP-18e column (100 × 9 × 4.6 mm) (Merck, Darmstadt, Germany). The elution was carried out using 0.1 m phosphoric acid, and the flow rate was 1 mL/min. The absorbance was monitored at 254 nm. L-ascorbic acid was identified by comparison with the standard. The calibration curve was prepared by plotting different concentrations of the standard vs. the area measurements in HPLC.

Statistical analysis

Statistical analysis was conducted using Statistica version 9.0 (StatSoft, Krakow, Poland). Significant differences ( 0.05) between means were evaluated by one-way anova and Duncan's multiple range test.

Results and discussion

  1. Top of page
  2. Summary
  3. Introduction
  4. Materials and methods
  5. Results and discussion
  6. Conclusions
  7. Acknowledgments
  8. References

Consumer evaluation of products

Results of consumer evaluation of smoothies are presented in Table 2A,B.

Table 2. (A) Consumer evaluation of apple and quince smoothies. (B) Consumer evaluation of chokeberry and black currant smoothies
SmoothiesQualitative discriminantTotal
ColourFlavourTasteConsistency
  1. Value are given as means (= 30).

(A)
Apple (A)
16.75 ± 1.917.50 ± 1.605.63 ± 1.775.50 ± 2.146.34
1′6.38 ± 2.077.00 ± 1.416.88 ± 1.555.13 ± 2.036.34
26.88 ± 2.036.75 ± 2.436.00 ± 1.855.88 ± 1.556.38
2′7.00 ± 2.076.75 ± 1.836.13 ± 2.305.75 ± 1.676.41
37.50 ± 1.516.75 ± 2.256.13 ± 2.596.75 ± 2.556.78
3′8.13 ± 1.466.75 ± 1.917.00 ± 2.627.00 ± 2.567.22
47.50 ± 2.676.75 ± 2.716.88 ± 2.756.13 ± 2.646.81
4′4.88 ± 2.306.38 ± 2.456.88 ± 2.805.13 ± 3.145.81
Quince (Q)
16.25 ± 2.715.88 ± 2.303.25 ± 1.835.13 ± 2.235.13
1′5.25 ± 2.496.25 ± 2.124.50 ± 2.205.13 ± 2.425.28
26.38 ± 2.626.63 ± 1.604.00 ± 1.855.25 ± 2.715.56
2′7.00 ± 2.676.50 ± 1.414.50 ± 2.565.13 ± 2.755.78
37.74 ± 2.057.75 ± 1.284.25 ± 1.396.13 ± 1.816.46
3′7.63 ± 2.397.63 ± 1.194.75 ± 2.125.88 ± 2.036.47
47.50 ± 2.738.13 ± 1.136.63 ± 2.266.88 ± 1.817.28
4′5.50 ± 2.457.00 ± 2.336.50 ± 2.456.88 ± 1.966.47
(B)
Black currant (B)
16.63 ± 2.134.63 ± 2.132.75 ± 1.673.88 ± 1.364.47
1′6.75 ± 1.163.63 ± 2.262.25 ± 1.583.38 ± 2.004.00
25.75 ± 1.044.50 ± 2.672.75 ± 1.584.00 ± 1.934.25
2′5.75 ± 1.394.25 ± 2.822.88 ± 1.643.75 ± 2.494.16
37.00 ± 1.315.88 ± 2.233.50 ± 2.075.13 ± 1.735.38
3′6.38 ± 1.305.00 ± 2.564.00 ± 2.514.38 ± 1.604.94
46.63 ± 0.924.88 ± 2.803.25 ± 2.924.25 ± 2.124.75
4′6.75 ± 1.045.38 ± 2.724.25 ± 3.014.38 ± 2.395.19
Chokeberry (C)
16.88 ± 1.553.88 ± 2.103.50 ± 2.885.38 ± 1.414.91
1′6.50 ± 1.414.13 ± 1.733.50 ± 2.564.13 ± 2.644.56
26.75 ± 1.165.00 ± 1.693.88 ± 2.305.00 ± 2.335.16
2′6.50 ± 1.205.00 ± 2.004.63 ± 2.264.88 ± 2.305.25
36.25 ± 1.917.25 ± 1.045.38 ± 1.776.38 ± 1.306.31
3′6.75 ± 1.496.38 ± 2.075.75 ± 2.386.13 ± 1.366.25
47.38 ± 1.417.13 ± 1.645.63 ± 1.515.00 ± 1.936.28
4′6.80 ± 1.136.38 ± 2.335.38 ± 2.335.25 ± 2.055.97

Higher notes were given in the consumer evaluation to the smoothies based on juices from pome fruits – apples (A) and quince (Q) than to those based on chokeberry (C) and black currant (B) juices. In turn, irrespective of product variant (A, Q, C and B), consumers indicated smoothies with the addition of cranberry and black currant puree (3 and 3′) and those with the addition of bilberry puree and cloud dog rose juice (4 and 4′) as more attractive. Definitely unacceptable turned out to be the smoothies enriched with puree from Japanese quince (1–1′) and sea buckthorn (2–2′). Even a small contribution of these fruits deteriorated flavour values of the smoothies, which had a negative effect on their overall sensory desirability. The unbeneficial effect of flowering quince and buckthorn on the taste of the samples was observed especially in the products based on chokeberry (C) and black currant (B) juices. It is common knowledge that berries of both black currant and chokeberry are characterised by specific flavour bouquet. Astringency of chokeberry fruits and high acidity of black currant fruits are sometimes not acceptable to consumers, especially if these berries are the basic component of processed products. The addition of puree from flowering quince and buckthorn was additionally intensifying the sour taste of the smoothies. These fruits are known for their high content of organic acids. Titratable acidity of Japanese quince juice ranges from 2.6 to 5.6 g of citric acid/100 mL (Ros et al., 2004), whereas that of buckthorn juice reaches even 6.2 g/100 mL (Yang, 2009). It is therefore possible that this quality attribute disturbed the perception of the remaining traits of the smoothies. According to Nadolna & Szponar (1998), the proportion of sweet and sour taste plays a significant role in the sensory assessment of foods. Smoothies Q1′ (containing 40 g of quince and 10 g of sea buckthorn puree), Q2 (25 g of dog rose and 25 g of Japanese quince puree) and Q2′ (40 g of dog rose and 10 g of Japanese quince puree), that were based on quince juice (100 g/150 g of product), received higher notes in consumer evaluation than their black currant counterparts (B1, B2 and B2′). Considering differences in the production technology of juices, but also in the structure of fruits themselves, it could be expected that no other but black currant-based smoothies would be characterised by more desirable consistency. The juice from quince contains a higher number of easily sedimenting particles than the black currant juice produced via enzymatic processing. Quince fruits are harder, and their parenchyma contains a significant number of sclerenchyma cells. They are also characterised by a specific, untypical aroma and astringent taste (Wojdyło, 2011). In spite of that, consumers were rather preferring the products based on quince than those based on black currant. It was noticed, however, that in ‘B’-type smoothies, the acceptance of consumers was linked with the intensity of black currant aroma and with perceptibility of black currant taste. The products with the highest contribution of black currant (B3) received the highest sensory notes. This dependency was also confirmed by Łysoniewska et al. (2011). In turn, Nadolna & Szponar (1998) and Reguła (2009) demonstrated that the quality of processed products from black currant fruits (beverages, nectars, juices) was affected, to the greatest extent, by the taste and aroma of black currant, as the most typical and identifiable with these fruits.

The proportions between contents of main and supplementary components of smoothies affected results of their organoleptic assessment to a various extent. Although the consumers were precise in indicating their preferences of fruit species choice (cranberry, black currant, bilberry, dog rose), they were not unanimous in determining the contribution of particular smoothies components. Amongst the smoothies based on quince juice (Q) and black currant juice (B), consumers appreciated those that contained equal proportions (25 g/150 g of product) of cranberry and black currant puree (Q3, B3) as well as bilberry puree and dog rose juice (Q4, B4). The apple smoothies (A) were the most appreciated by the consumers when the contribution of black currant puree reached 40 g/150 g of smoothies (A3′). A more preferable composition of the smoothies containing dog rose juice (25 g) and bilberry puree (25 g) was indicated for the A4 sample. In turn, the chokeberry smoothies were receiving higher notes in consumer evaluation when having equal contents of cranberry and black currant puree (C3). A higher content of dog rose juice (40 g) compared with the bilberry puree (10 g) had also a positive impact on smoothies acceptability (C4′).

Contents of polyphenols and antioxidative activity of smoothies

The products selected by the sensory panel in consumer evaluation were compared in terms of the total content and profile of polyphenolic compounds (Fig. 1). The samples were analysed, by means of the liquid chromatography technique, for contents of polymers of proanthocyanidins (PA), phenolic acids (FA), flavonols (F) and anthocyanins (A). The highest content of polyphenols was determined in the smoothies based on berry fruit juices: chokeberry (442.40 mg/100 g on average) and black currant (263.02 mg/100 g on average). Compounds with a structure of polymerised proanthocyanidins were found to predominate in most of the products, except for the black currant smoothies (B3) where the main group of polyphenols were anthocyanins. The content of proanthocyanidins was higher in the smoothies containing dog rose juice, with the highest content of these compounds determined in the sample C4′ (351.46 mg/100 g). Dog rose is a valuable source of nonhydrolysing tannins, including tetra- and trimers with the structure of aglycones, mono- and diglycosides (Salminem et al., 2005). Also, chokeberry fruits are characterised by a high concentration of PA. Over 80% of proanthocyanidins identified in chokeberry fruits have a polymeric structure, whereas the remaining 20% are represented by tannins with a lower molecular mass, composed mainly of three to nine flavanol units (Gu et al., 2004).

image

Figure 1. Content and profile of chosen smoothies polyphenols (mg/100 g fw).

Download figure to PowerPoint

In the analysed smoothies, the content of phenolic acids ranged from 5.19 mg/100 g (apple smoothies A3′) to 78.46 mg/100 g (chokeberry smoothies C3). In a study on berry fruits, Mattila et al. (2006) demonstrated that chokeberry was a valuable source of phenolic acids (96 mg/100 g). A higher content of these compounds was noted only in rowanberries. The smoothies with the addition of dog rose juice and bilberry puree were, generally, more rich in the investigated phenolic compounds. Only in the case of chokeberry smoothies was the content of phenolic acids significantly higher in the sample containing cranberry and black currant puree (C3). The phenolic acids profile of mixed fruit products results mainly from the specific chemical composition of fruits they were made of. In view of the results achieved in this study, it may be concluded that the type of base juice applied was the factor that differentiated phenolic compounds abundance in the smoothies.

In the analysed smoothies, the least numerous, in terms of content, group of polyphenols were flavonols. When flavonols content in smoothies was considered as affected by the type of base juice, the highest values were determined in those based on black currant (22.99 and 22.06 mg/100 g in samples B3 and B4, respectively). The smoothies with the addition of cranberry and black currant puree (variant 3 or 3′) were characterised by a higher content of these compounds than those with dog rose juice and bilberry puree (4 or 4′). A high concentration of flavonols in fruits of black currant and cranberry distinguishes them from other berry species, including raspberries, red currant (Borges et al., 2010), strawberries, chokeberry and bilberry (Häkkinen, 2000). Fruit composition of the smoothies affected also the content of anthocyanins which ranged from 8.66% (Q4) to 45.26% (B3) of the total polyphenols. A higher content of the red pigments was found mainly in the smoothies with the addition of bilberry puree and dog rose juice, compared with those containing cranberry and black currant puree.

The analysed products were also compared in terms of their antioxidative properties (Fig. 2). Statistically significant differences were found between the smoothies in the activity against ABTS cation radical. Simultaneously, the analysis of variance showed that their health-promoting potential was not correlated with results of their organoleptic assessment. The strongest antioxidative properties were expressed by the chokeberry smoothies (C) that were little acceptable in consumer evaluation. The apple and quince smoothies (A, Q), acknowledged by the sensory panel as the most attractive products, were characterised by even fivefold lower Trolox equivalent antioxidant capacity (TEAC) values.

image

Figure 2. Antioxidant activity of smoothies, measured by ABTS method (letters a–g means statistically homogenous groups,  0.05).

Download figure to PowerPoint

Worthy of emphasising is, however, that the antiradical potential of the analysed smoothies was higher compared with that of the commercially available ones. Müller et al. (2010) determined the antioxidative activity of 14 commercial samples of smoothies at a level of 0.34 – 1.28 mmol TE/100 g. The product characterised by the highest reactivity against ABTS (1.28 mmol TE/100 g) contained 9 different fruit and vegetable components, including, for example, apple puree (31%), carrot juice (29%), apple juice concentrate (25%) and strawberry puree (4%). The apple and quince smoothies produced under laboratory conditions contained only 3 fruit components; however, their antiradical potential was over 6.00 mmol TE/100 g (sample Q4). Simultaneously, these smoothies were receiving high notes in the organoleptic assessment. Hence, it may be concluded that smoothies may be produced not only from popular species of fruits (e.g. black currant, apples) but also from less-known fruits, including dog rose, quince or cranberry. The use of these components in appropriate proportions enabled developing a food product not only characterised by high health-promoting values, but also highly acceptable by consumers.

The correlation analysis demonstrated that the antioxidative potential of the smoothies was correlated not with the total content of polyphenols but rather with their chemical structure (Table 3). With account taken of conditions of the statistical test (theoretical r = 0.707, significance level  0.05), it was found that these properties were attributable exclusively to polymers of proanthocyanidins (r = 0.904). It is also the explanation of the previously observed relationship between antioxidant activity in chokeberry smoothies (high TEAC values) and acceptance by consumers (low ratings). This is due to high levels of PAs in those products. Proanthocyanidins give fruits the astringency, which negative influence on taste of products. Nowadays, consumer preference still be strongly related to the overall flavour of the different mixtures than interest of potential of antioxidant activity and the polyphenol contribution.

Table 3. Correlation between phenolic content and antioxidant activity of smoothies
 Proanthocyanidins/ABTSPhenolic acids/ABTSFlavonols/ABTSAnthocyanins/ABTS
r- correlation factor0.9040.4890.1060.527

No correlation was observed between contents of anthocyanins (r = 0.527), phenolic acids (r = 0.489) and flavonols (r = 0.106) and the activity against ABTS cation radical, although it is common fact that the antioxidative potential of plants and their products is attributable to phenolic compounds, including anthocyanins.

Polyphenols content of food products allows determining their antiradical properties on condition of considering their amount, type and origin. Hence, in complex systems, attention should be paid not to the action of individual compounds but rather to the effects of the whole group of compounds and interactions between them. Investigations conducted by Hidalgo et al. (2010) showed explicitly that these reactions were not always synergistic in nature.

The issue of a correlation between the antioxidative activity and concentration of phenolic compounds in food products has been extensively addressed in literature, although conclusions were sometimes conflicting. Some scientists failed to find any correlation between content of phenols and antioxidative activity in plant extracts (Gil et al., 2002), whereas others pointed to strong correlations between them (Sun et al., 2002; Cioroi & Musat, 2007; Dodonne et al., 2009).

Content of ascorbic acid

The samples of smoothies were also analysed for the content of ascorbic acid (AA), and respective results were presented in Fig. 3. The analysed products differed significantly in the content of vitamin C, the highest content of ascorbic acid was determined in black currant smoothies B4 with the addition of dog rose juice and bilberry puree (168.98 mg/100 g on average). A similar content of AA was found in C4′ sample (chokeberry smoothies). This indicates a positive effect of Rosa canina juice addition on smoothies enrichment with vitamin C. An analogous dependency was observed in apple (A) and quince (Q) smoothies. The content of ascorbic acid in these products was twofold and fourfold higher than in, respectively, A3′ and Q3 samples without the dog rose juice. The advisability of applying natural means to fortify fruit products with vitamin C results from many reasons. The addition of AA has a positive effect on colour stabilisation in processed fruit products. It is of great significance especially in the processing of fruits with bright parenchyma susceptible to enzymatic browning, for example, apples or pears. It is also possible to use the synthetic form of vitamin C as an antioxidant in the technological process (Özoğlu & Bayındırlı, 2002; Markowski et al., 2009). However, the application of synthetic preparations of biologically active compounds should be minimised in the production of so-called biofood. Instead, contents of fruits being their natural sources, for example, pseudo-rose hip, should be increased in recipes of such food products, as they are a highly concentrated source of many compounds with health-promoting properties, AA in particular. Ercisli (2007) reports that the content of vitamin C in pseudo-rose hip varies between 727 and 943 mg/100 g, depending on species. In the case of cloudy apple juices, where product quality is indicated by the preservation of the natural, bright-cream colour, Japanese quince fruits may be used as a source of vitamin C. The content of AA in Japanese quince juice may reach even 112 mg/100 mL (Ros et al., 2004). Another advantage of processed products from both mentioned species is their similar colour.

image

Figure 3. Ascorbic acid content (mg/100 g fw) in apple, quince, chokeberry and black currant smoothies (letters A–H means statistically homogenous groups,  0.05).

Download figure to PowerPoint

Conclusions

  1. Top of page
  2. Summary
  3. Introduction
  4. Materials and methods
  5. Results and discussion
  6. Conclusions
  7. Acknowledgments
  8. References

Fruits of the temperate climatic zone were characterised by high usability for the production of smoothies. Their products were attractive to consumers and, what is more important, constituted a valuable source of polyphenolic compounds. As it results from the sensory assessment, the panellists were most in favour of the smoothies containing puree from berry fruits (cranberry and black currant) as well as juice from dog rose and puree from bilberry. The degree of consumer acceptance of the smoothies was higher in the case of products based on apple or quince juice. The highest content of polyphenols was determined in chokeberry (C) and black currant (B) smoothies. The antioxidative properties of smoothies were mainly affected by the content of polymerised forms of proanthocyanidins occurring in fruits. Irrespective of the production variant (smoothies A, Q, C or B), higher contents of ascorbic acid were found in the smoothies with the addition of rose hip juice (4 or 4′); however, the highest content of vitamin C, reaching 170 mg, was assayed in the smoothies based on black currant juice.

Acknowledgments

  1. Top of page
  2. Summary
  3. Introduction
  4. Materials and methods
  5. Results and discussion
  6. Conclusions
  7. Acknowledgments
  8. References

This work was supported by the European Union under Project No. POIG 01.01.02-00-061/09, acronym ‘Bioactive food’. We thank Maria Bortkiewicz and Elzbieta Bucka for technical assistant.

References

  1. Top of page
  2. Summary
  3. Introduction
  4. Materials and methods
  5. Results and discussion
  6. Conclusions
  7. Acknowledgments
  8. References
  • Auger, C., Kim, J.-H., Trinh, S., Chataigneau, T., Popken, A.M. & Schini- Kerth, V.B. (2011). Fruit juice-induced endothelium-dependent relaxations in isolated porcine coronary arteries: evaluation of different fruit juices and purees and optimization of a red fruit juice blend. Food & Function, 2, 245250.
  • Borges, G., Degeneve, A., Mullen, W. & Crozier, A. (2010). Identification of flavonoid and phenolic antioxidants in black currants, blueberries, raspberries, red currants, and cranberries. Journal of Agricultural and Food Chemistry, 58, 39013909.
  • Boyer, J. & Liu, R.H. (2004). Apple phytochemicals and their health benefits. Nutrition Journal, 3 in http://www.nutritionj.com/content/3/1/5.
  • British Soft Drinks Association (2011). The 2011 UK Soft Drinks Report. By popular demand. Available at: http://www.britishsoftdrinks.com/PDF/2011%20soft%20drinks%20report.pdf.
  • Cioroi, M. & Musat, C.L. (2007). Investigations on the correlations between polyphenol content from red wines and their antioxidant capacity. Cercetari Agronomice in Moldova, Anul XXXX 4, 3540.
  • Dodonne, S., Vitrac, X., Coutiere, P., Woillez, M. & Merillon, J.-M. (2009). Comparative study of antioxidant properties and total phenolic content of 30 plant extracts of industrial interest using DPPH, ABTS, FRAP, SOD and ORAC assays. Journal of Agricultural and Food Chemistry, 57, 17681774.
  • Ercisli, S. (2007). Chemical composition of fruits in some rose (Rosa spp.) species. Food Chemistry, 104, 13791384.
  • Gil, M.I., Tomás- Barberán, F.A., Hess- Pierce, B. & Kader, A.A. (2002). Antioxidant capacities, phenolic compounds, carotenoids, and vitamin C contents of nectarine, peach, and plum cultivars from California. Journal of Agricultural and Food Chemistry, 50, 49764982.
  • Gu, L., Kelm, M.A., Hammerstone, J.F. et al. (2004). Concentrations of proanthocyanidins in common foods and estimations of normal consumption. The Journal of Nutrition, 134, 613617.
  • Häkkinen, S. (2000). Flavonols and phenolic acids in berries and berry products. Doctoral dissertation, Publications D. Medical Sciences 221. 2000. 90 p.
  • Hidalgo, M., Sánchez-Moreno, C. & de Pascual-Teresa, S. (2010). Flavonoid–flavonoid interaction and its effect on their antioxidant activity. Food Chemistry, 121, 691696.
  • Jakobek, L., Seruga, M., Medvidovic- Kosanovic, M. & Novak, I. (2007). Anthocyain content and antioxidant activity of various red fruits juices. Deutsche Lebensmittel- Rundschau, 2, 5864.
  • Jaros, D., Thamke, I., Raddatz, H. & Rohm, H. (2008). Single-cultivar cloudy juice made from table apples: an attempt to identify the driving force for sensory preference. European Food Research Technology, 222, 5161.
  • Keenan, D.F., Brunton, N.P., Gormley, T.R., Butler, F., Tiwari, B.K. & Patras, A. (2010). Effect of thermal and high hydrostatic pressure processing on antioxidant activity and colour of fruit smoothies. Innovative Food Science and Emerging Technologies, 11, 551556.
  • Kennedy, J.A., Hayasaka, Y., Vidal, S., Waters, E.J. & Jones, G.P. (2001). Composition of grape skin proanthocyanidins at different stages of berry development. Journal of Agricultural and Food Chemistry, 49, 53485355.
  • Łysoniewska, E., Kalisz, S. & Mitek, M. (2011). Sensory quality of black currants nectars and beverages enriched with echinacea and green tea extracts. ŻYWNOŚĆ Nauka Technologia Jakość, 6, 167177.
  • Markowski, J., Baron, A., Mieszczakowska, M. & Plocharski, W. (2009). Chemical composition of French and Polish cloudy apple juices. Journal of Horticultural Science & Biotechnology, ISAFRUIT Special Issue, 52, 6874.
  • Mattila, P., Hellström, J. & Törrönen, R. (2006). Phenolic acids in berries, fruits, and beverages. Journal of Agricultural and Food Chemistry, 54, 71937199.
  • Müller, L., Gnoyke, S., Popken, A.M. & Böhm, V. (2010). Antioxidant capacity and related parameters of different fruit formulations. LWT - Food Science and Technology, 43, 992999.
  • Nadolna, I. & Szponar, L. (1998). Fruit and Vegetables Juices in Health Promotion. IŻŻ, Warsaw.
  • Oszmiański, J., Wolniak, M., Wojdylo, A. & Wawer, I. (2007). Comparative study of polyphenolic content and antiradical activity of cloudy and clear apple juices. Journal of the Science of Food and Agriculture, 87, 573579.
  • Özoğlu, H. & Bayındırlı, A. (2002). Inhibition of enzymic browning in cloudy apple juice with selected antibrowning agents. Food Control, 13, 213221.
  • Oszmiański, J. & Wojdyło, A. (2009). Effects of blackcurrant and apple pulp blended on phenolics, antioxidant capacity and colour of juices. Journal Czech Food Technology, 27, 338351.
  • Piljac- Zegarac, J., Valek, L., Martinez, S. & Belscak, A. (2009). Fluctuations in the phenolic content and antioxidant capacity of dark fruit juices in refrigerated storage. Food Chemistry, 113, 394400.
  • Qian, N. (2006). Fruit and vegetable smoothies, and its processing method. Faming Zhuanli Shenqing Gongkai Shuomingshu. CN 1817192.
  • Re, R., Pellegrini, N., Proteggente, A., Pannala, A. & Yang, M. (1999). Antioxidant activity applying an improved ABTS radical cation decolorization assay. Free Radical Biology & Medicine, 26, 12311237.
  • Reguła, J. (2009). Nutritive value and organoleptic properties of cookies with the addition of dried shitake mushroom (Lentinula Edodes). Żywność Nauka Technologia Jakość, 4, 7985.
  • Ros, J.M., Laencina, J., Hellin, P., Jordan, M.J., Vila, R. & Rumpunen, K. (2004). Characterization of juice in fruits of different Chaenomeles species. LWT - Food Science and Technology, 37, 301307.
  • Ruxton, C.H.S. (2008). Smoothies: one portion or two? British Nutrition Foundation Nutrition Bulletin, 33, 129132.
  • Salminem, J.-P., Karonen, M., Lempa, K. et al. (2005). Characterisation of proanthocyanidin aglycones and glycosides from rose hips by high-performance liquid chromatography–mass spectrometry, and their rapid quantification together with vitamin C. Journal of Chromatography A, 1077, 170180.
  • Sun, J., Chu, Y.F., Wu, X. & Liu, R.H. (2002). Antioxidant and antiproliferative activities of common fruits. Journal of Agriculture and Food Chemistry, 50, 74497454.
  • Watzl, B. (2008). Smoothies – wellness aus der Flasche? Ernährungsumschau, 6, 352353.
  • Wojdyło, A. (2011). The evaluation of quince fruit use in the production of preserves with high polyphenol content and antioxidant activity. Monographs CXVIII. ISSN 1898-1151.
  • Wojdyło, A., Oszmiański, J. & Laskowski, P. (2008). The polyphenolic compounds and antioxidant activity of new and old apple varieties. Journal of Agriculture and Food Chemistry, 56, 65206530.
  • Wojdyło, A., Oszmiański, J., Teleszko, M. & Sokół-Łętowska, A. (2013). Composition and quantification of major polyphenolic compounds, antioxidant activity and colour properties of quince and mixed quince jams. International Journal of Food Science and Food Nutrition. doi:10.3109/09637486.2013.793297. [Epub ahead of print].
  • Yang, B. (2009). Sugars, acids, ethyl b-D-glucopyranose and a methyl inositol in sea buckthorn (Hippophaë rhamnoides) berries. Food Chemistry, 112, 8997.