Improved analysis of anthocyanins and vitamin C in blue-purple potato cultivars

Lemon juice pretreatment as a strategy to preserve the quality and enhance the texture of cooked potato slices of different sizes

Potatoes are an important food crop worldwide and are rich in essential nutrients. However, cooking can reduce their nutritional value and alter their texture. This study aimed to investigate the impact of pretreating potato slices with lemon juice. The slices were immersed in 5% lemon juice solution for 3 h, rinsed with distilled water for another 3 h, then cooked at 100°C for 20 min. Findings revealed that lemon juice pretreatment (LJP) notably improved the texture, mouthfeel, and overall acceptability of the cooked potato slices of different sizes (CPS-Ds). Additionally, LJP significantly increased vitamin C and total phenolic contents, slightly decreased pH levels, and preserved the desired color of CPS-Ds. Consumer sensory evaluations also indicated a positive response to LJP samples, suggesting its potential application in the food industry. The study confirmed that LJP is an effective, sustainable, consumer-friendly, and cost-efficient technique for improving the quality of cooked potato slices.

Effect of Acylated and Nonacylated Anthocyanins on Urine Metabolic Profile during the Development of Type 2 Diabetes in Zucker Diabetic Fatty Rats

The effect of nonacylated and acylated anthocyanins on urinary metabolites in diabetic rats was investigated. Nonacylated anthocyanins extract from bilberries (NAAB) or acylated anthocyanins extract from purple potatoes (AAPP) was given to Zucker diabetic fatty (ZDF) rats for 8 weeks at daily doses of 25 and 50 mg/kg body weight. ¹H NMR metabolomics was applied to study alterations in urinary metabolites from three time points (weeks 1, 4, and 8). Both types of anthocyanins modulated the metabolites associated with the tricarboxylic acid cycle, gut microbiota metabolism, and renal function at weeks 1 and 4, such as 2-oxoglutarate, fumarate, alanine, trigonelline, and hippurate. In addition, only a high dose of AAPP decreased monosaccharides, formate, lactate, and glucose levels at week 4, suggesting improvement in energy production in mitochondria, glucose homeostasis, and oxidative stress. This study suggested different impacts of AAPP and NAAB on the metabolic profile of urine in diabetes.

Profiling beneficial phytochemicals in a potato somatic hybrid for tuber peels processing: phenolic acids and anthocyanins composition

The purpose of this study was to characterize the peels of a CN1 somatic hybrid obtained from two dihaploid potato lines (Cardinal H14 and Nicola H1) in terms of the health-promoting phenolic compounds (phenolic acids and anthocyanins). The CN1 hybrid is defined by a pink tuber skin color making it different from the light-yellow-skinned "Spunta," which is the most commonly grown potato cultivar in Tunisia. Oven-dried peel samples derived from CN1 hybrid and cv. Spunta were ground, and phenolic compounds were extracted with water or methanol for quantification. Lyophilized peels were used for the phenolic acid and anthocyanin analyses. Higher total quantities of phenolic compounds were recovered in methanol extracts compared with water extracts. A slightly higher concentration of phenolic acids (100 mg/100 g DW) was obtained in the lyophilized peels extract of CN1 hybrid than in the cv. Spunta corresponding sample (83 mg/100 g DW). The profiles of the chlorogenic acid isomers were almost identical in both of CN1 hybrid and cv. Spunta. Caffeic acid (CA) and three caffeoylquinic acids (CQAs): 3-CQA, 4-CQA, and 5-CQA, were identified from both genotypes, 5-CQA being the dominant form in both potatoes. Since the CN1 hybrid has a pink skin color, its anthocyanin profile was also determined. The anthocyanin quantity in the CN1 peels was 5.07 mg/100 g DW, involving six different anthocyanins that were identified within the extract, namely, Pelargonidin-3-rutinoside-5-glucoside, peonidin-3-rutinoside-5-glucoside, coumaroyl ester of pelargonidin-3-rutinoside-5-glucoside, coumaroyl ester of peonidin-3-rutinoside-5-glucoside, feruloyl ester of pelargonidin-3-rutinoside-5-glucoside, and feruloyl ester of peonidin-3-rutinoside-5-glucoside. These results suggest that the peel waste of CN1 somatic hybrid can be considered as a promising source of high-value compounds for food industry.

The Influence of the Production Process on the Anthocyanin Content and Composition in Dried Potato Cubes, Chips, and French Fries Made from Red-Fleshed Potatoes

The stability of acylated anthocyanins is still a new and unexplored subject of study. The changes in the contents of individual anthocyanins in colored-flesh potato tubers during processing have rarely been addressed in the literature. The aim of the present study was to determine how anthocyanin degradation and profiles are influenced in potatoes of the red-fleshed Herbie 26 variety by different methods of processing. Potato samples were divided into four categories to be analyzed, namely, raw material, potato cubes, French fries, and chips. The dried cubes, French fries, chips, semi-finished products, and finished products, obtained through laboratory processing, were examined for anthocyanin content and composition. The production process of cubes, chips, and French fries led to losses of the examined anthocyanins; however, these losses differed depending on the technological stage. The greatest losses of these compounds were determined after the final production processes, i.e., pre-frying, frying, and drying. Chip production led to the lowest losses of anthocyanins. Omitting the blanching stage in chip production allowed the retention of more anthocyanins. Pelargonidin-3-feruloylrutinoside-5-glucoside, having the highest percentage in the raw material (approximately 50%), followed by pelargonidin-3-caffeoylrutinoside-5-glucoside, proved to be the most thermally stable.

Impact of cultivar, growth temperature and developmental stage on phenolic compounds and ascorbic acid in purple and yellow potato tubers

Phenolic compounds and ascorbic acid were analyzed in one yellow and four purple-flesh potato cultivars grown at 13 °C and 18 °C and harvested at different stages of tuber development, using HPLC-DAD and UHPLC-MS. The expression of genes in the phenylpropanoid pathway was studied at transcription level using qPCR. Petunidin-3-p-coumaroylrutinoside-5-glucoside was the most abundant anthocyanin in 'Blue Congo', 'Blaue Schweden', and 'Synkeä Sakari', whereas malvidin-3-p-coumaroylrutinoside-5-glucoside dominated in 'Blaue Veltlin'. In mature tubers, the purple cultivar 'Synkeä Sakari' showed the highest content of anthocyanins (2.4 mg/g freeze-dried sample), and 'Blaue Veltlin' had the highest content of phenolic acids (5.5 mg/g). Cultivar was the main variable affecting the biosynthesis of the studied metabolites, whereas the temperatures studied did not show different impact. The content of the main phenolic acids and anthocyanins in the potato cultivars correlated positively with the expression levels of the genes involved in the phenylpropanoid pathway.

New UHPLC-QqQ-MS/MS Method for the Rapid and Sensitive Analysis of Ascorbic and Dehydroascorbic Acids in Plant Foods

A new method using ultra high-performance liquid chromatography coupled with triple quadrupole mass spectrometry (UHPLC-QqQ-MS/MS) methodology was developed for the determination of ascorbic acid (AA) and dehydroascorbic acid (DHAA) contents in liquid and solid vegetable samples. The advantages of this method are speed, high sensitivity and practical application. In accordance with these advantages, the present method allows the simultaneous determination of AA and DHAA without previous reduction/derivatization of DHAA and without the use of internal standards in the samples. This is of high interest in routine analysis, providing a simpler sample preparation, as well as enhanced accuracy and robustness. Its validation included selectivity, sensitivity and linearity, precision and accuracy, matrix effect, and recovery. The results showed high selectivity and sensitivity, with calibration curves ranging from 10 to 500 ng mL⁻¹ and from 50 to 500 ng mL⁻¹ for AA and DHAA, respectively. Appropriate dilutions for each sample are necessary to avoid the matrix effect with accepted recoveries.

Effect of the frying process on the composition of hydroxycinnamic acid derivatives and antioxidant activity in flesh colored potatoes

Phenolic composition of potatoes (Solanum tuberosum) with colored flesh has been previously reported, highlighting their anthocyanin composition. However, there is less information available about the profiles and concentrations of hydroxycinnamic acid derivatives (HCADs) in these potatoes. In pigmented potatoes from Southern Chile, three HCADs have been detected, corresponding to the trans isomers of 3-, 4- and 5-caffeoylquinic acid. It is remarkable that after frying, the HCAD concentrations increased 493% compared to those of fresh potatoes. The same tendency has been observed for total phenols and antioxidant activity of the chips. The results obtained are relevant in relation to the classification of pigmented potatoes as functional foods not only due to their anthocyanin content but also due to their higher content of HCADs, especially since their concentration increases considerably after frying, thus contributing to their antioxidant activity and potential beneficial effects for human health compared with uncolored genotypes.

Characterization of interactions of eggPC lipid structures with different biomolecules

In this paper we study the interactions of two biomolecules (ascorbic acid and Annonacin) with a bilayer lipid membrane. Egg yolk phosphatidylcholine (eggPC) liposomes (in crystalline liquid state) were prepared in solutions of ascorbic acid (AA) at different concentration levels. On the other hand, liposomes were doped with Annonacin (Ann), a mono-tetrahydrofuran acetogenin (ACG), which is an effective citotoxic substance. While AA pharmacologic effect and action mechanisms are widely known, those of Ann's are only very recently being studied. Both Fourier Transformed Infrared (FTIR) and Raman spectroscopic techniques were used to study the participation of the main functional groups of the lipid bilayer involved in the membrane-solution interaction. The obtained spectra were comparatively analyzed, studying the spectral bands corresponding to both the hydrophobic and the hydrophilic regions in the lipid bilayer. Electrochemical experiments namely; impedance spectroscopy (EIS) and cyclic voltamperometry (CV) were used as the main characterization techniques to analyse stability and structural changes of a model system of supported EggPC bilayer in connection with its interactions with AA and Ann. At high molar ratios of AA, there is dehydration in both populations of the carbonyl group of the polar head of the lipid. On the other hand, Ann promotes the formation of hydrogen bonds with the carbonyl groups. No interaction between AA and phosphate groups is observed at low and intermediate molar ratios. Ann is expected to be able to induce the dehydration of the phosphate groups without the subsequent formation of H bonds with them. According to the electrochemical analysis, the interaction of AA with the supported lipid membrane does not alter its dielectric properties. This fact can be related to the conservation of structured water of the phosphate groups in the polar heads of the lipid. On the other hand, the incorporation of Ann into the lipid membrane generates an increase in the number of defects while changes the dielectric constant. This, in turn, can be associated with the induced dehydration of the phosphate groups.