ACTA Scientiarum Polonorum - Technologia Alimentaria News en (c) Wydawnictwo Uniwersytetu przyrodniczego w Poznaniu Solid-Phase Extraction (SPE): Principles and Applications in Food Samples

Solid-Phase Extraction (SPE) is a sample preparation method that is practised on numerous application fields due to its many advantages compared to other traditional methods. SPE was invented as an alternative to liquid/liquid extraction and eliminated multiple disadvantages, such as usage of large amount of solvent, extended operation time/procedure steps, potential sources of error, and high cost. Moreover, SPE can be ap- plied to the samples combined with other analytical methods and sample preparation techniques optionally. SPE technique is a useful tool for many purposes through its versatility. Isolation, concentration, purification and clean-up are the main approaches in the practices of this method. Food structures represent a complicated matrix and can be formed into different physical stages, such as solid, viscous or liquid. Therefore, sample preparation step particularly has an important role for the determination of specific compounds in foods. SPE offers many opportunities not only for analysis of a large diversity of food samples but also for optimization and advances. This review aims to provide a comprehensive overview on basic principles of SPE and its applications for many analytes in food matrix.

Elicitation and treatment with precursors of phenolics synthesis improve low-molecular antioxidants and antioxidant capacity of buckwheat sprouts

Background. Recently, an increase of interest in the modification of food products on each step of production (breeding, production technology, storage condition) is observed. Nutritional properties as well as level and activity of bioactive compounds in plant-origin food may be modified using a range of technological and biotechnological practices and elicitation should be mentioned between them.

Material and methods. Elicitation with willow bark infusion supported by feeding with the phenylpropa- noid pathway precursors were used for improving the quality of buckwheat sprouts. Special emphasis has been placed on the metabolomic and biochemical changes and the mechanism of overproduction of low-molecular antioxidants.

Results. The accumulation of phenolics is caused by stimulation of two main enzymes the phenylpropanoid pathway (tyrosine ammonia-lyase and phenylalanine ammonia-lyase). Tyrosine ammonia-lyase activities were effectively induced by feeding with tyrosine (about four times that of the control), whereas phenylala- nine ammonia-lyase activity was the highest in the elicited control sprouts and those fed with shikimic acid (an increase by 60% compared to the control). Shikimic acid feeding (both elicited and non-elicited sprouts) effectively improved the total phenolics (by about 10% and 20%, respectively), condensed tannins (by about 30% and 28%, respectively), and flavonoids (by about 46% and 70%, respectively). Significant increase of vitexin, rutin, chlorogenic acid and isoorientin contents was also observed. The treatments increased the ascorbic acid content, too. Total antioxidant capacity of sprouts was most effectively increased by feeding with shikimic acid and further elicitation.

Conclusion. The studies transfer biotechnology commonly used for the induction of overproduction of sec- ondary metabolites in plant cell line systems to low-processed food production. The obtained results could be used for better understanding of the effect of elicitation and precursor feeding on antioxidants production and contribute to improving the buckwheat sprouts quality.

The eff ect of addition of selected milk protein preparations on the growth of Lactobacillus acidophilus and physicochemical properties of fermented milk

Background. The intake of fermented milk products, especially yoghurts, has been systematically increasing for a few decades. The purpose of this work was to obtain milk products fermented with a mix of bacterial cultures (yoghurt bacteria and Lactobacillus acidophillus LA-5) and enriched with selected milk protein preparations. Secondly, the aim of the work was to determine physiochemical and rheological properties of the obtained products.
Material and methods. The following additives were applied in the experiment: whey protein concen- trate (WPC 65), whey protein isolate (WPI), demineralised whey powder (SPD), caseinoglycomacropeptide (CGMP), α-lactalbumin (α-la), sodium caseinate (KNa) and calcium caseinate (KCa). Milk was fermented using probiotic strain Lactobacillus acidophillus LA-5 and a typical yoghurt culture. The products were analysed in terms of the survivability of bacterial cells during refrigerated storage, rheological properties and syneresis. Fermented milk products were obtained using blends of bacterial strains: ST-B01:Lb-12 (1:1), ST-B01:Lb-12:LA-5 (1:1:2).
Results. Milk beverages fermented with typical yoghurt bacteria and LA-5 strain showed intensive syner- esis. The addition of LA-5 strain caused formation of harder acid gels, comparing to typical yoghurts. Milk products which were prepared from skimmed milk possessed higher values of hardness and consistency coefficient. The increase of concentrations of milk preparations (except of WPI) did not cause significant differences in the hardness of acidic gels obtained by fermentation of mixed culture with a probiotic strain. Conclusion. The applied preparations improved physiochemical properties of the milk beverages which were prepared with a probiotic strain. The increase of protein milk preparations concentration resulted in a gradual decrease of the secreted whey. Among the products that were made of full milk powder and were subjected to three weeks of refrigerated storage the highest survivability of Lb. acidophilus LA-5 was noticed in the samples fortified with 1% WPC.

The infl uence of the dose of calcium bisglycinate on physicochemical properties, sensory analysis and texture profi le of kefi rs during 21 days of cold storage

Background. In the process of enrichment of dairy products a priority element is the proper selection of com- pounds that are a mineral carrier. Calcium bisglycinate is better absorbed by the body than inorganic forms of calcium. Moreover, the lactic acid which is produced in kefir fermentation and the presence of lactose have also a positive effect on the improvement of absorption of calcium. The aim of the present study was to deter- mine the influence of the applied dose of calcium in the form of calcium bisglycinate on the physicochemical and sensory properties and texture of kefirs during 21-day period of cold storage.
Material and methods. Processed cow milk was enriched with 0, 5, 10, 15, 20, 25 and 30 mg of calcium (for 100 g of milk), repasteurized (72°C, 1 min), cooled down (26°C), inoculated with Commercial VITAL kefir culture (Danisco, Poland) and fermented for 16 hours (26°C). The assessment of the influence of addition   of calcium bisglycinate on acidity, syneresis, texture and sensory characteristics (1–9 points) of kefirs was conducted at four fixed dates (after 1 day, 7 days, 14 days and 21 days of storage).
Results. During successive weeks of cold storage in all experimental groups there was observed a tendency to decrease general acidity. On the 1st and 7th days of cold storage reduced whey leakage was observed in kefirs enriched with 25 mg and 30 mg Ca/100 g of milk. With increasing doses of enrichment with calcium both the hardness, adhesiveness and gumminess of kefirs decreased. The applied doses of calcium did not cause changes in the sensory characteristics such as colour and consistency of the fermented beverages.
Conclusions. Calcium bisglycinate may be used to enrich kefirs with calcium even with 30 mg of calcium in 100 g of milk without the modification of the product’s parameters.

Tapioca maltodextrin in the production of soft unripened cheese

Background. An excessive consumption of fat has been associated with an increased risk of health problems such as obesity, diabetes and cardiovascular diseases. Cheese is a highly concentrated product which is rich in protein and minerals such as calcium and phosphorus and essential amino acids, therefore it is an important food in the diet. But low fat cheeses are usually characterized as having poor body and flavour. Therefore,  it is crucial to find ways of improving the acceptability of the product. The aim of this research was to inves- tigate the possibility of using of tapioca maltodextrin in the production of soft cheese made from ultrafiltrated skimmed milk and to create organoleptic properties of a fat product in a non-fat product.
Material and methods. To estimate the possibility of using tapioca maltodextrin in the production of soft cheese, the influence of tapioca maltodextrin on rennet flocculation time (RFT) and rennet clotting time (RCT), pH values, moisture content were estimated. Improving the quality of cheese, rheological and sensory characteristics in the course of soft unripened cheese manufacturing has to be focused on.
Results. Using tapioca maltodextrin led to decrease in RFT and RCT. The concentration increase of the maltodextrin in milk for cheese production led to increase in moisture-binding capacity and moisture content of the cheeses, but led to decrease in RFT, RCT and pH-value. Based on the experiments data the optimal doses of tapioca maltodextrin were recommended.
Conclusions. An addition of tapioca maltodextrin resulted in a tendency of decreasing RFT and RCT,   pH-value for cheese made with different concentrations of tapioca maltodextrin when compared to cheese made without maltodextrin addition. At the same time an increased amount of tapioca maltodextrin led to moisture content increase of cheese samples. Inclusion of tapioca maltodextrin in natural, low fat cheese may improve texture and acceptability as compared to low fat control cheeses without maltodextrin. The recommended level of tapioca maltodextrin is 1.1% of the mixture weight.

Effects of solvents and extraction methods on the content and antiradical activity of polyphenols from fruits Actinidia arguta, Crataegus monogyna, Gaultheria procumbens and Schisandra chinensis

Background. In line with the current tendency towards the production of the so-called safe foods, the use of environmentally-friendly methods for the extraction of polyphenols from fruits has been sought. Citric acid is a good solvent in the preparation of phenolic compounds for the food and pharmaceutical industries because it is a natural antioxidant and is non-toxic for the environment. Furthermore, new sources of polyphenols from fruit of orchard plants that are less known in Poland have been looked for. The aim of this study was  to assess the content and antiradical activity of polyphenolic compounds in fruit extracts, depending on the extraction method employed. In addition, the yield of extraction processes was assessed.
Material and methods. The experimental materials were fruits of the following plants: Actinidia arguta, Crataegus monogyna, Gaultheria procumbens, Schisandra chinensis. For the extraction, aqueous solutions of citric acid (CAE) and methanol (ME) were used. The following were determined in fruit extracts: the con- tent of total phenols (TP) and anthocyanins (A), and antiradical activity (DPPH and ABTS).
Results. In general, the C. monogyna fruit extracts were distinguished by the highest TP and A content. The TP and A content was significantly higher in fruit extracts obtained with the CAE method than in the ones produced with the ME method. The highest mean A/TP ratio was determined for S. chinensis fruit extracts. The antiradi- cal activity (DPPH and ABTS) in fruit extracts did not depend on an extraction method, but on fruit species. Overall, a higher yield of extraction processes was achieved for the CAE method than for the ME method.
Conclusions. The present study indicates that the selected extraction methods are able to obtain polyphenolic extracts from fruits with a high antiradical activity and high yield. The use of citric acid in order to extract polyphenols from fruits may be an alternative to the conventional extraction method, while being eco-friend- ly and more effective than the latter.

Optimization of extraction parameters on the antioxidant properties of banana waste

Background. Banana is grown worldwide and consumed as ripe fruit or used for culinary purposes. Peels form about 18–33% of the whole fruit and are discarded as a waste product. With a view to exploiting banana peel as a source of valuable compounds, this study was undertaken to evaluate the effect of different extrac- tion parameters on the antioxidant activities of the industrial by-product of banana waste (peel).
Materials and methods. Influence of different extraction parameters such as types of solvent, percentages of solvent, and extraction times on total phenolic content (TPC) and antioxidant activity of mature and green peels of Pisang Abu (PA), Pisang Berangan (PB), and Pisang Mas (PM) were investigated. The best extrac- tion parameters were initially selected based on different percentages of ethanol (0–100% v/v), extraction time (1–5 hr), and extraction temperature (25–60°C) for extraction of antioxidants in the banana peels. Total phenolic content (TPC) was evaluated using Folin-Ciocalteu reagent assay while antioxidant activities (AA) of banana peel were accessed by DPPH, ABTS, and β;-carotene bleaching (BCB) assays at optimum extrac- tion conditions.
Results. Based on different extraction solvents and percentages of solvents used, 70% and 90% of acetone had yielded the highest TPC for the mature and green PA peels, respectively; 90% of ethanol and methanol has yielded the highest TPC for the mature and green PB peels, respectively; while 90% ethanol for the mature and green PM peels. Similar extraction conditions were found for the antioxidant activities for the banana peel assessed using DPPH assay except for green PB peel, which 70% methanol had contributed to the highest AA. Highest TPC and AA were obtained by applying 4, 1, and 2 hrs extraction for the peels of PA, PB and PM, respectively. The best extraction conditions were also used for determination of AAs using ABTS and β;-carotene bleaching assays. Therefore, the best extraction conditions used have given the highest TPC and AAs.
Conclusions. By-products of banana (peel) can be considered as a potential source of antioxidants in food and pharmaceutical industry.

Eff ect of oil fl ushing with nitrogen on the quality and oxidative stability of coldpressed rapeseed and sunfl ower oils

Background. Oxidative stability means resistance to oxidation during purchase, processing and storage and is a key quality indicator of edible fats. Oils ought to be stored in dark-glass bottles, at low temperatures  and with no access of light in order to effectively preserve their oxidative stability. Since all vegetable oils contain unsaturated fatty acids that can react with oxygen and deteriorate over time, displacement of oxygen with inert gases may result in a reduction of the rate of oxidation. In the study the effect of oil flushing with nitrogen on the quality and oxidative stability of cold-pressed rapeseed and sunflower oils was determinate.
Material and methods. Commercial samples of cold-pressed rapeseed and sunflower oils were stabilized by generating anaerobic atmosphere in the bottles by blowing through with nitrogen and generation of a “nitro- gen cushion”. Oils were tested in accelerated at 63°C and long-term at 20°C storage tests.
Results. After 20 days of Schaal oven test, the peroxide value in the flushing with nitrogen rapeseed and sunflower oils was, respectively, 4 and 7 times lower than in the control samples (without nitrogen). In turn, of the long-term storage test (with access of light 20°C), the peroxide value of oil flushing with nitrogen after 6 months of storage was 2.3 to 2.8-fold lower, respectively, than in the control sample. In the oil samples flushed with nitrogen peroxide formation was inhibited, however, as a result of the breakdown of the perox- ides already existed in the oil, gradual decrease of the oxidative stability (determined via Rancimat test) was observed along with prolonged storage of oils.
Conclusions. Oil flushing with nitrogen was a very effective way to reduce the changes caused by oxidation in cold-pressed rapeseed and sunflower oil.

Oat raw materials and bakery products – amino acid composition and celiac immunoreactivity

Background. The aim of this study was to compare the biochemical and immunochemical properties of avenins in some special oat raw materials and additionally the possibility of using them as a raw material for the gluten-free bakery products.
Materials and methods. The compared oat raw materials were – oat flakes, commercial oat flours (includ- ing gluten-free oat flour) and residual oat flour, which is by-product of β;-glucan preparation. Biochemical characteristic included amino acid compositions and SDS-PAGE profiles of extracted avenins. The immuno- chemical reactivity with polyclonal anti-gluten and monoclonal anti-gliadin antibodies was evaluated quali- tatively and quantitatively by immunoblotting and ELISA methods. Additionally, experimental bakery prod- ucts made of examined raw materials were assessed according to their suitability for the celiac patients’ diet. Results. The highest protein content was measured in the β;-glucan preparation “Betaven“ and gluten-free oat flour. Proteins of all materials are rich in glutamic and aspartic acid, leucine and arginine. Proportions of amino acids in avenins extracted from most of oat raw materials are similar, excluding gluten-free oat flour, which has a very low avenin content and proportions of individual amino acids are different. The SDS-PAGE protein pattern consisted of proteins with molecular weight of about 25–35 kDa. Polyclonal anti-gluten anti- body recognized all protein fractions of molecular weight higher than 20 kDa. Quantitative ELISA analysis shows that the majority of samples has a gliadin-like protein content within the range of 80–260 mg/kg, excluding gluten-free flours and corresponding bakery products. Altogether, β;-glucan preparation has ex- tremely high level of gliadin-like proteins.
Conclusion. In the examined oat raw materials and foods the contents of immunoreactive amino acid se- quences exceeded the limit of 20 mg/kg (considered as gluten-free) except for gluten-free flours (oat and  the prepared mixture) and the bakery products based on gluten-free flours. Unfortunately, the rest of oat raw materials and products cannot be considered gluten-free.

Decreased adipose tissue zinc content is associated with metabolic parameters in high fat fed Wistar rats

Background. Limited data on adipose tissue zinc content in obesity exist. At the same time, the association between adipose tissue zinc content and metabolic parameters in dietary-induced obesity is poorly studied. Therefore, the primary objective of this study is to assess adipose tissue zinc content and its association  with morphometric parameters, adipokine spectrum, proinflammatory cytokines, and apolipoprotein profile in high fat fed Wistar rats.
Material and methods. A total of 48 adult female Wistar rats were used in the present study. Rats were fed either control (10% of fat) or high fat diet (31.6% of fat). Adipose tissue zinc content was assessed using inductively coupled plasma mass spectrometry. Rats’ serum was examined for adiponectin, leptin, insulin, interleukin-6, and tumor necrosis factor-α using enzyme-linked immunosorbent assay kits. Serum glucose and apolipoprotein spectrum were also evaluated.
Results. High fat feeding resulted in a significant 34% decrease in adipose tissue zinc content in comparison to the control values. Fat pad zinc levels were significantly inversely associated with morphometric param- eters, circulating leptin, insulin, tumor necrosis factor-α levels and HOMA-IR values. At the same time,      a significant correlation with apolipoprotein A1 concentration was observed.
Conclusion. Generally, the obtained data indicate that (1) high fat feeding results in decreased adipose tis- sue zinc content; (2) adipose tissue zinc content is tightly associated with excessive adiposity, inflammation, insulin resistance and potentially atherogenic changes.

Twelve weeks CLA supplementation decreases the hip circumference in overweight and obese women. A double-blind, randomized, placebo-controlled trial

Background. Conjugated linoleic acid (CLA) reduces body weight (BW), body fat mass (BFM), and in- creases or maintains lean body mass in animals. However, the results concerning the effect of CLA on weight reduction in humans are contradictory. The present study aimed to evaluate the effect of CLA supplementa- tion on the BW and anthropometric parameters (waist and hip circumferences) in overweight and obese adult women.
Material and methods. A total of 74 subjects (BMI: 28–42 kg/m2) were included in a double blind, placebo- controlled trial. Subjects were randomized into two groups, those supplemented with either 3.0 g/d CLA or with placebo (sunflower oil) for 12 weeks.
Results. CLA significantly decreased the hip circumferences compared to placebo (p = 0.016209), but had no effect on body weight, BMI, or waist circumference. The number of subjects with a reduction in hip circum- ference in the CLA group was significantly larger compared to that in the placebo group (p = 0.0017;  NNT= 2.65; CI [6.27–1.685]).
Conclusions. In conclusion, our findings do not support the hypothesis that 12 weeks CLA supplementation, as dosed in the present study, is effective for body weight reduction in overweight and obese women. How- ever, its local action in decreasing the hip circumference seems to be encouraging and suggests that CLA may represent an attractive dietary supplement.