Validation and application of a standardized procedure for evaluating freshness of Citrus juices based on pectin methylesterase activity quantitation

A method developed for freshness authentication of freshly squeezed Citrus juices (FSCJ) was evaluated for routine application. It involved titrimetric assessment of pectin methylesterase (PE) activity after enzyme extraction from pulp-standardized juice samples. Standard test conditions enabled reliable discrimination between FSCJ and chilled Citrus juices that had comparative advantages due to extended shelf life. Unlike the latter, FSCJ always displayed PE activities in the linear range between the limit of identification (LOI, 0.42 units g-1 of juice) and the maximum activity found for FSCJ (1.94 units -1), equivalent to 0.0035-0.016 units during titration. However, for model samples having activities < LOI due to production by respective dilution of FSCJ, the responses abruptly fell to unspecific levels below the limit of detection (LOD, 0.21 units g-1). Accuracy was substantiated by 100 -106 % recovery for model juices with PE activities of 0.87 -1.22 units g-1 resulting from FSCJ dilution or PE standard addition, but it was lower (76 - 80 %) near LOI. The average of the mean activities, which were detected by 3 analysts with intraassay precision ≤ 8.4 %, varied with relative standard deviations of 8.2 % for FSCJ and 3.9 % for a sample of the same juice diluted to 60 % (w/w), thus proving reproducibility. FSCJ batches were unambiguously distinguished from four commercial chilled juices, because the activities detected for the latter were by far ≤ LOD and thus confirmed labeled mild preservation

Accumulation of carbohydrates and pungent principles in characteristic seed and set grown onion varieties (Allium cepa L.)

The profile of carbohydrates of onions (Allium cepa L.), mainly consisting of fructooligosaccharides (FOS), has a strong impact on digestibility, processability and storability. This study focused on the accumulation of FOS and pungent principles in onions during bulb maturation. Different onion varieties were grown from both, seedsand sets. Total FOS concentrations in onions of cv. ‘Sturon’ were higher when grown from sets than from seeds throughout the entire maturation period, reaching final levels of 75.7 ± 2.2 and 61.8 ± 11.8 g/L FOS, respectively. Higher levels in set grown onions might be due to their earlier emergence, thus resulting in an extended photosynthetically active period (+12% total sunshine hours). However, seed grown, so-called dehydrator onions (cv. ‘Stardust’) had significantly higher FOS contents than set grown cv. ‘Sturon’ onions at all sampling points (final FOS level: 129.3 ± 16.6 g/L), indicating cultivar-dependant accumulation. Furthermore, dehydrator onions accumulated FOS with highest molecular weight and a unique FOS distribution, allowing clear discrimination of such dehydrator cultivars. Besides carbohydrates, pungency as indicated by pyruvic acid levels was shown to be determined by sulphurous fertilization and its timing

Ultrasound-assisted extraction and (U)HPLC-DAD-ESI-MSn analysis of phenolic compounds from black chokeberries cultivated in Turkey

Phenolic compounds from two black chokeberry cultivars 'Viking' and 'Nero' grown in Turkey were analyzed by high performance liquid chromatography-diode array detection-electrospray ionization-multistage mass spectrometry (HPLC-DAD-ESI-MSn). In the first step, five different solvents were compared to efficiently isolate phenolic compounds by ultrasound-assisted extraction. Three sequential extraction cycles using methanol/formic acid (95:5, v/v) sufficed for exhaustive extraction of anthocyanins, hydroxycinnamic acid derivatives, and flavonol glycosides from black chokeberry within merely 60 sec. A total of four cyanidin glycosides, two hydroxycinnamic acids, and five quercetin mono- and diglycosides were detected in both cultivars. Total anthocyanins (425-438 mg/100 g of fresh weight, FW), hydroxycinnamic acids (173-179 mg/100 g of FW), and flavonols (37 mg/100 g of FW) were determined in a similar range for both cultivars. Complementary, a rapid ultra-high performance liquid chromatography (UHPLC)-DAD method was developed, permitting a high throughput screening of chokeberry phenolics. The established methods were validated considering extraction recoveries, intra- and inter-day repeatability, calibration linearity, limit of detection (LOD), and limit of quantitation (LOQ). UHPLC provided a 2.3 times faster compound separation (30 min) and less solvent consumption than HPLC (68 min)

Effects of cultivation year and growing location on the phenolic profile of differently coloured carrot cultivars

Carrots (Daucus carota L.) are economically and nutritionally important crops that, apart from carotenoids, contain numerous phenolic compounds which are assumed to exert health beneficial effects. The total phenolic contents of fruits and vegetables are known to depend on cultivar and growing conditions; however, studies examining the variability of a collection of carrots comprising differently coloured cultivars are rare. Therefore, the objective of the present study was to investigate the phenolic compounds of ten differently coloured carrot cultivars considering the effects of three cultivation years at two growing locations. Although total phenolic contents varied in a wide range, both purple cultivars ‘Anthonina’ and ‘Deep Purple’ significantly exceeded those of yellow, orange, red, and uncoloured cultivars (P ≤ 0.05) with amounts from 4,113 to 11,737 mg [kg dry matter (DM)]-1. In contrast to the purple roots, the other generally were characterised by far lower polyphenol contents ranging from 33 to 1,369 mg (kg DM)-1. Interestingly, the values did not considerably vary within these cultivars. In the present study, contrary to cultivar specific effects, the infl uence of growing location was found to be rather weak, supposedly due to similar climatic conditions at both locations. Similarly, variation of phenolic contents from year-to-year was less pronounced. In conclusion, the selection of breeding material was found to be of utmost importance regarding the expression of polyphenols in differently coloured carrots

Detection of isorhamnetin glycosides in extracts of apples (Malus domestica cv. ‘Brettacher’) by HPLC-DAD and HPLC-APCI-MSy MS.

Extracts of apple fruits (Malus domestica cv. &quot;Brettacher&quot;) were analysed by HPLC with photodiode array detection. An unknown peak was monitored displaying the same retention time as isorhamnetin 3-Oglucoside. Preliminary identification of the isorhamnetin aglycone was performed by comparison of UV spectral data of the unknown compound with a reference substance. Using atmospheric pressure chemical ionisation mass spectrometry in the negative ion mode, the presence of an isorhamnetin glycoside was supported by loss of 162 amu from the pseudomolecular ion (m/z 477). MS 2 product ion analysis of the parent ion m/z 477 provided a fragmentation pattern identical to the reference. Collision-induced dissociation of the aglycone (m/z 315) in the MS 3 product ion analysis allowed the differentiation of rhamnetin and isorhamnetin, and unambiguous assignment by comparison with standard compounds. A second isorhamnetin glycoside eluting prior to the glucoside was tentatively identified as isorhamnetin 3-Ogalactoside. To the best of our knowledge, this is the first report of isorhamnetin glycosides in apple fruit extracts. Results are discussed with respect to chemotaxonomic relevance within the genera Malus and Pyrus, and especially in consideration of the control of the authenticity of apple products

Processing and storage of innovative pasty parsley (Petroselinum crispum (MILL.) NYM EX A. W. HILL) and celeriac (Apium graveolens L. var. rapaceum (MILL.) DC.) products

A process for the production of innovative pasty parsley and celeriac products was developed. Freshly harvested plant material was blanched, processed into a paste, and subsequently heated for 3 min at 90 and 95 °C, respectively. Chlorophyll stability was not affected by the thermal process due to the addition of 0.05% (m/v) MgCl2 to the blanching water. In all products, the contents of the main phenolic compound apiin decreased, while those of the minor compound malonylapiin B increased. In parsley pastes, peroxidase (POD) and polyphenol oxidase (PPO) were fully inactivated by the heat treatment. In contrast, only complete PPO inactivation was achieved in celeriac pastes. However, since POD inactivation was incomplete, its partial reactivation during storage of celeriac pastes was observed. After 4 weeks of cold storage, the green color of the parsley pastes turned into an olive hue due to chlorophyll degradation. Nevertheless, the products may be stored at -20 °C for several months. In contrast, storage of celeriac pastes at 4 and -20 °C is possible for several months without darkening. Compared to conventional dried herbs and spices the products obtained by the innovative process are characterized by bright colors. Pasty products are easier to handle, because lumping and dusting are avoided, thus facilitating their safe application in the food processing industry

Contribution of peptides and polyphenols from olive water to acrylamide formation in sterilized table olives

To confirm the role of peptides as principal precursors of acrylamide formation in sterilized table olives, peptides from olive water were fractionated. After their partial fractionation by solid phase extraction (SPE) and ultrafiltration (<10,000Da), respectively, small peptides from olive water were isolated by size-exclusion chromatography (SEC). In the fractions collected, peptides and polyphenolic compounds were determined colorimetrically, and acrylamide was quantitated by LC-MS/MS after heating of the samples. Subsequently, peptides were characterized by matrix-assisted laser desorption/ionization-tandem time of flight mass spectrometry (MALDI-TOF/TOF-MS), and polyphenols were analyzed by LC-MS in the respective fractions. Finally, peptides containing fractions were purified on a polymeric resin (Amberlite XAD 16HP) to remove unbound phenolic compounds by adsorption. The results of the different experiments performed in complete absence of free asparagine and reducing sugars strongly support small peptides bound to polyphenols to be the principal precursors of acrylamide in sterilized table olives. © 2014 Elsevier Ltd.This work was supported in part by the European Union (FEDER funds) and the Spanish government through Project AGL 2010-19178. The Spanish government is also thanked for the fellowship of the first author.Peer Reviewe

Acrylamide in Table Olives

23 PáginasAcrylamide is formed in two types of table olives where heat sterilization is applied, namely, in California-style black ripe olives and, to a lesser extent, in California-style green ripe olives. In contrast, acrylamide is not detected in other processing types such as Spanish-style and Greek-style olives, where pasteurization is sufficient for their preservation. This chapter describes the steps for the preparation of black ripe olives, and their influence on acrylamide levels in the final product. Strategies to mitigate acrylamide formation in table olives, including modifications of processing method and the use of additives, are reviewed. Finally, recent research on the identification of precursors of acrylamide in olives is summarized. It is suggested that peptide-bound polyphenols may form acrylamide following sterilization without the involvement of free asparagine and reducing sugars. Since acrylamide was formed from small model peptides at temperatures far exceeding 121 °C, namely from protein-bound alanine adjacent to amino acids carrying a ß-H atom, the contribution of quinones and dialdehydes acting as activating carbonyl components is assumed. Ongoing studies are focused on elucidating the exact formation mechanism of acrylamide in table olives. © 2016 Elsevier Inc. All rights reservedPeer reviewe