Monitoring of acrylamide and phenolic compounds in table olive after high hydrostatic pressure and cooking treatments

A lutein and zeaxanthin enriched extra virgin olive oil as a potential nutraceutical agent: A pilot study

Xanthophylls lutein and zeaxanthin are carotenoids with important antioxidant capacities and relevant roles against the prevention of eye diseases. In this study a valorization of non-commercial spinach to obtain lutein and zeaxanthin as raw materials to develop nutraceuticals was carried out. Three oil matrixes were analyzed: extra virgin olive oil (EVOO), lutein and zeaxanthin enriched EVOO (EVOO+LZ), and EVOO enriched with 25 % of EVOO+LZ (namely EVOO+D) to evaluate their biological potential as antioxidants. Urinary antioxidant total capacity, and circulatory blood levels of lutein and zeaxanthin were determined (in vivo analysis). Also, a simulation of gastrointestinal simulation (in vitro analysis) was performed. The results showed an increase in the circulatory levels of lutein-zeaxanthin after the ingestion of EVOO+LZ during 45 and 60 days, and an increase in the urinary antioxidant levels after the intake of EVOO+LZ and EVOO+D. In vitro assay revealed that both xanthophylls showed bioavailability to be assimilated in the intestinal tract. Therefore, these EVOO enriched with lutein-zeaxanthin might be considered as powerful antioxidant tools with potential properties in the management/prevention of eye diseases.

Effect of elaboration process, crop year and irrigation on acrylamide levels of potential table olive varieties

BACKGROUND

Table olives are widely consumed in the Mediterranean diet, and several typical Spanish and Portuguese varieties could potentially be used as such. In order to ensure a good-quality product, the effect of different factors such as elaboration processes, irrigation conditions, crop year and their crossover interaction on acrylamide content and antioxidant compounds needs to be deeply studied.

RESULTS

When looking through irrigation, regulated deficit irrigation (RDI) presented lower acrylamide levels than rainfed conditions for 'Cordovil de Elvas', 'Picual' and 'Verdeal Alentejana'. No significant interactions were found between the type of irrigation and elaboration style for 'Arbequina' and 'Koroneiki' varieties. Although RDI had the largest concentration of total phenols, antioxidant activity was also the highest. The table olives harvested in the crop year of 2019 showed lower levels of acrylamide due to a significant relationship between the crop year and irrigation conditions.

CONCLUSIONS

Novel varieties to be marketed should be taken into consideration for table olive elaboration. The impact of the crop year on the bioactive value of table olives and crossover interactions relies strongly in climatological conditions. Last but not least, the benefit of selecting the best irrigation and elaboration methods is crucial to ensure desirable acrylamide levels. © 2023 Society of Chemical Industry.

Heat-Introduced Formation of Acrylamide in Table Olives: Analysis of Acrylamide, Free Asparagine, and 3-Aminopropionamide

Acrylamide was detected in considerable amounts in black table olives. In this study, besides black, also green and naturally black table olives were investigated for their acrylamide, free asparagine, and 3-aminopropionamide contents before and after heat treatment. Acrylamide amount was 208-773 μg/kg in black table olives and did not change due to heat treatment. In green and naturally black table olives acrylamide was ≤24 μg/kg before heat treatment and rose to 1200 μg/kg afterward. Asparagine content was 0.35-35 mg/kg in all samples before heat treatment and after heat treatment with no considerable change in the range. 3-Aminopropionamide showed amounts of ≤56 μg/kg in the unheated samples and increased up to 131 μg/kg due to heat impact. However, quantified asparagine and 3-aminopropionamide amounts were insufficient in almost all samples to explain the acrylamide quantities formed due to heat treatment based on the formation via the Maillard reaction.

Burn Defect and Phenol Prediction for Flavoured Californian-Style Black Olives Using Digital Sensors

Californian-style black olives can undergo different chemical changes during the sterilization process that can affect their sensory and phenol characteristics. Thus, these olives were stuffed with flavoured hydrocolloids and submitted to different thermal sterilization treatments to assess sensory categories. The triangular test indicated that the panellists were able to discriminate between samples from different categories according to their aromas with more than 85% success. The results indicated that the negative aroma detected by tasters was related to burn defects. The highest level of defects was found in standard olives, while the lowest was identified in the extra category. Furthermore, olives submitted to the lowest thermal sterilization treatment (extra) presented significantly higher phenol profile content, such as for hydroxytyrosol, tyrosol, oleuropein and procyanidin B1. The electronic nose (E-nose) discriminated between samples from different categories according to the specific aroma (PC1 = 82.1% and PC2 = 15.1%). The PLS-DA classified the samples with 90.9% accuracy. Furthermore, the volatile organic compounds responsible for this discrimination were creosol, copaene, benzaldehyde and diallyl disulphide. Finally, the models established by the PLS analysis indicated that the E-nose could predict olives according to their aroma and total phenol profile (RCV2 values were 0.89 and 0.92, respectively). Thus, this device could be used at the industrial level to discriminate between olives with different sensory aromas to determine those with the highest quality.

Bioavailability of Phenolic Compounds in Californian-Style Table Olives with Tunisian Aqueous Olive Leaf Extracts

Recent advances in biotechnology have ensured that one of the main olive tree by-products is olive leaf extract (OLE), a rich source in bioactive compounds. The aim of this work was to study the phenolic composition in different OLEs of three Tunisian varieties, namely, 'Sayali', 'Tkobri', and 'Neb Jmel'. The in vitro biodigestibility effect after 'Sayali' OLE addition to Californian-style 'Hojiblanca' table olives was also studied. This OLE contained bioactive molecules such as hydroxytyrosol, tyrosol, oleropeine, Procianidine B1 (PB1), and p-cumaric acid. These compounds were also found in fresh olives after OLE was added. Furthermore, from fresh extract to oral digestion, the detected amount of bioavailable phenol was higher; however, its content decreased according to each phase of gastric and intestinal digestion. In the final digestion phase, the number of phenols found was lower than that of fresh olives. In addition, the phenolic content of Californian-style 'Hojiblanca' table olives decreased during the in vitro digestion process. The antioxidant activity of this variety decreased by 64% and 88% after gastrointestinal digestion, being the highest antioxidant capacity found in both simulated gastric and intestinal fluid, respectively. The results show us that the 'Sayali' variety is rich in phenolic compounds that are bioavailable after digestion, which could be used at an industrial level due to the related health benefits.

Evaluation of Tunisian Olive Leaf Extracts to Reduce the Bioavailability of Acrylamide in Californian-Style Black Olives

The aim of this work was analyzing the use of olive leaf extracts (OLE) obtained from two local Tunisian olive tree cultivars 'Chemlali' and 'Sayali' to reduce the acrylamide in Californian-style black olives. The phenol profile, antioxidant, and antibacterial activity of the two OLE extracts were evaluated. The principal phenols found were hydroxytyrosol (1809.6 ± 25.3 mg 100 g^-1), oleuropein (2662.2 ± 38 mg 100 g^-1) and luteolin-7-O-glucoside (438.4 ± 38 mg 100 g^-1) presented higher levels in 'Sayali' variety. Small differences were observed between the two kinds of extracts used; the greatest activity of OLE was observed against S. choleraesuis, with values up to 50% inhibition. The extract of 'Chemlali' cultivar was added to the Californian-style table olive, improving its phenol content and its antioxidant characteristics without negatively affecting its sensorial characteristics; these olives showed the highest firmness and proper quality characteristics. The gastrointestinal activity on the acrylamide concentration showed a partial degradation of this compound through the digestion, although the addition of the extract does not seem influence in its gastrointestinal digestion. These findings prove the usefulness of by-products to generate a high-quality added-value product, and this would also be relevant as a step towards a more sustainable, circular economy model.

Hydroxytyrosol in Foods: Analysis, Food Sources, EU Dietary Intake, and Potential Uses

Hydroxytyrosol (HT) is a phenolic compound with proven biological properties present in a limited number of foods such as table olives, virgin olive oil (VOO) and wines. The present work aims to evaluate the dietary intake of HT in the European (EU) population by compiling scattered literature data on its concentration in foods. The consumption of the involved foods was estimated based on the EFSA Comprehensive European Food Consumption Database. The updated average contents of HT are as follows: 629.1, 5.2 and 2.1 µg/g for olives, olive oil and wine, respectively. The HT estimated intake in the European Union (EU) adult population falls within 0.13–6.82 mg/day/person, with table olives and wine being the main contributors. The estimated mean dietary intake of HT in EU countries is 1.97 ± 2.62 mg/day. Greece showed the highest HT intake (6.82 mg/day), while Austria presented the lowest (0.13 mg/day). Moreover, HT is an authorized novel food ingredient in the EU that can be added to different foods. Since the estimated HT intake is substantially low, the use of HT as a food ingredient seems feasible. This opens new possibilities for revalorizing waste products from olive oil and olive production which are rich HT sources.

Masking Effect of Cassia grandis Sensory Defect with Flavoured Stuffed Olives

Carao (Cassia grandis) is an America native plant characterized by its high iron content. This particular property allows its use as a natural additive to fix the black colour in California-style black olives, while masking its unpleasant aroma by stuffing olives with flavoured hydrocolloid. The tasting panel evaluated olives filled with unflavoured hydrocolloid with a fruity aroma, classified them as an extra category. Olives with the Carao addition presented a positive aroma, but also showed negative sensory attributes such as cheese, fermented and metallic flavours/aromas. The aroma of lyophilized Carao was better than the fresh one. The ‘Mojo picón’ aroma masked defective olives, allowing their classification from the second to the first commercial category. The volatile compounds belonged to the following families: terpenes, hydrocarbons, and oxygenated compounds, while the minor ones were alcohols and acid derivatives. The main volatile compounds identified were dialyl disulphide and 3-methyl-butanoic acid; among the minor ones were 2,4-dimethyl-hexane and dimethyl-silanediol and nonanal. Addition of fresh Carao increased the unpleasant aroma provoked by 3-methyl-butanoic acid, 2-methyl-butanoic acid and (E)-2-Decenal. Finally, an electronic device was able to discriminate these aromas and the results obtained agreed with those of the tasting panel and the volatile compounds.

Application of Digital Olfaction for Table Olive Industry

The International Olive Council (IOC) established that olives must be free of odors, off-flavors, and absent of abnormal ongoing alterations or fermentations. The use of electronic devices could help when classifying defects in a fast, non-destructive, cheap, and environmentally friendly way. For all of that, table olives were evaluated according to IOC regulation in order to classify the defect predominant perceiving (DPP) of the table olives and their intensity. Abnormal fermentation defects of Spanish-style table olives were assessed previously by an IOC-validated tasting panel. 'Zapateria', 'Putrid', and 'Butyric' were the defects found at different concentrations. Different volatile compounds were identified by gas chromatography in altered table olives. The same samples were measured with an electronic nose device (E-nose). E-nose data combined with chemometrics algorithms, such as PCA and PLS-DA, were able to successfully discriminate between healthy and non-healthy table olives, being this last one also separated between the first and second categories. Volatile compounds obtained with gas chromatography could be related to the E-nose measuring and sensory analysis, being capable of matching the different defects with their correspondents' volatile compounds.

Electronic nose application for the discrimination of sterilization treatments applied to Californian-style black olive varieties

BACKGROUND

Olive oil continues to be the main destination for olives. The production of table olives is increasing. 'Californian-style' processes are among the most frequently employed to produce oxidized olives. Sensory evaluation requires the development of an instrumental detection method that can be used as an adjunct to traditional tasting panels.

RESULTS

An electronic nose (E-nose) was used to classify two varieties of olives following exposure to different sterilization. Principal component analysis (PCA) revealed that both varieties had different volatile profiles. Sensory panel evaluations were similar for both. Partial least squares-discriminant analysis (PLS-DA) obtained from the E-nose was able to separate the two varieties and explained 82% of total variance. Moreover, volatile profiles correctly classified olives according to sterilization times recorded up to 121 °C . The only exception was at F₀  ≥ 22 min, at which a plot of PCA outcomes failed to differentiate scores. E-nose data showed similar results to those produced from the volatile analysis when grouping samples were sterilized to F₀  ≥ 18 min, at the same time distinguishing these samples from those subjected to less intense thermal treatments. A partial least squares (PLS) chemometric approach was evaluated for quantifying important olive quality parameters. With regards to validation parameters, R P 2 pertaining to perceived defect was 0.88, whilst R P 2 pertaining to overall assessment was 0.78.

CONCLUSIONS

E-nose offers a fast, inexpensive and non-destructive method for discriminating between varieties and thermal treatments up to a point at which cooking defects are highly similar (from F₀  = 18 onwards). © 2021 Society of Chemical Industry.

Characterization of Polyphenol and Volatile Fractions of Californian-Style Black Olives and Innovative Application of E-nose for Acrylamide Determination

Californian-style black olives require a sterilization treatment that produces a carcinogenic contaminant, acrylamide. Thus, this compound was evaluated in two different olive cultivars using an electronic nose (E-nose). The sterilization intensity had a significant influence on the final phenol concentrations, acrylamide content, and volatile compounds. Increasing the sterilization intensity from 10 to 26 min (F0) reduced the phenol content, but it promoted acrylamide synthesis, leading to a wide range of this toxic substance. The Ester and phenol groups of volatile compounds decreased their content when the sterilization treatment increased; however, aldehyde and other volatile compound groups significantly increased their contents according to the thermal treatments. The compounds 4-ethenyl-pyridine, benzaldehyde, and 2,4-dimethyl-hexane are volatile compounds with unpleasant odours and demonstrated a high amount of influence on the differences found after the application of the thermal treatments. The “Manzanilla Cacereña” variety presented the highest amount of phenolic compounds and the lowest acrylamide content. Finally, it was found that acrylamide content is correlated with volatile compounds, which was determined using multiple linear regression analysis (R² = 0.9994). Furthermore, the aroma of table olives was analysed using an E-nose, and these results combined with Partial Least Square (PLS) were shown to be an accurate method (range to error ratio (RER) >10 and ratio of performance to deviation (RPD) >2.5) for the indirect quantification of this toxic substance.

Effects of Different Controlled Temperatures on Spanish-Style Fermentation Processes of Olives

This work aimed to determine the effect of applying different temperatures during the fermentation process of Spanish-style table olives. ‘Manzanilla de Sevilla’ (southwest of Spain, Badajoz) and ‘Manzanilla Cacereña’ (northwest of Spain, Caceres) olives were processed at an industrial scale in table olive fermenters whose brine was subjected to different thermal treatments. One of the three conducted experiments found that maintaining brine at 20–24 °C over a 3-month period led to optimum firmness, better color indices, and greater free acidity and lactic acid bacteria populations in comparison to an unheated control. Furthermore, raising the temperature of the fermenter to 20–24 °C accelerated the fermentation process, provoking better lactic bacteria and yeast growth without affecting olive firmness. The higher fermentation rate (shorter time to completion) associated with temperature-controlled olives also reduced the marketing time of the final product. Controlling brine temperature led to a better aspect and color, higher acidity, lower bitterness, and better overall assessment of processed olives. In addition, ‘Manzanilla de Sevilla’ olives presented a higher phenolic content than ‘Manzanilla Cacereña’ olives. Preliminary evidence is presented suggesting that ‘Manzanilla Cacereña’ olives appear highly amenable to Sevillian-style processing. The present innovative work demonstrates the importance of applying different thermal treatments to brine to control the temperature during the industrial fermentation of table olives during the cold season.

Food By-Products to Extend Shelf Life: The Case of Cod Sticks Breaded with Dried Olive Paste

Recently, the interest in recovery bioactive compounds from food industrial by-products is growing abundantly. Olive oil by-products are a source of valuable bioactive compounds with antioxidant and antimicrobial properties. One of the most interesting by-products of olive oil obtained by a two-phase decanter is the olive paste, a wet homogeneous pulp free from residuals of the kernel. To valorize the olive paste, ready-to-cook cod sticks breaded with dried olive oil by-products were developed. Shelf-life tests were carried out on breaded cod sticks and during 15 days of storage at 4 °C pH evolution, microbiological aspects, and sensory properties were also monitored. In addition, the chemical quality of both control and active samples was assessed in terms of total phenols, flavonoids, and antioxidant activity. The enrichment with olive paste increased the total phenols, the flavonoids, and the antioxidant activity of the breaded fish samples compared to the control. Furthermore, the bioactive compounds acted as antimicrobial agents, without compromising the sensory parameters. Therefore, the new products recorded a longer shelf life (12 days) than the control fish sample that remained acceptable for nine days.

Effect of Microwave Heating on the Acrylamide Formation in Foods

Acrylamide (AA) is a neurotoxic and carcinogenic substance that has recently been discovered in food. One of the factors affecting its formation is the heat treatment method. This review discusses the microwave heating as one of the methods of thermal food processing and the influence of microwave radiation on the acrylamide formation in food. In addition, conventional and microwave heating were compared, especially the way they affect the AA formation in food. Available studies demonstrate differences in the mechanisms of microwave and conventional heating. These differences may be beneficial or detrimental depending on different processes. The published studies showed that microwave heating at a high power level can cause greater AA formation in products than conventional food heat treatment. The higher content of acrylamide in microwave-heated foods may be due to differences in its formation during microwave heating and conventional methods. At the same time, short exposure to microwaves (during blanching and thawing) at low power may even limit the formation of acrylamide during the final heat treatment. Considering the possible harmful effects of microwave heating on food quality (e.g., intensive formation of acrylamide), further research in this direction should be carried out.

Industrial Strategies to Reduce Acrylamide Formation in Californian-Style Green Ripe Olives

Acrylamide, a compound identified as a probable carcinogen, is generated during the sterilization phase employed during the processing of Californian-style green ripe olives. It is possible to reduce the content of this toxic compound by applying different strategies during the processing of green ripe olives. The influence of different processing conditions on acrylamide content was studied in three olives varieties (“Manzanilla de Sevilla”, “Hojiblanca”, and “Manzanilla Cacereña”). Olives harvested during the yellow–green stage presented higher acrylamide concentrations than green olives. A significant reduction in acrylamide content was observed when olives were washed with water at 25 °C for 45 min (25% reduction) and for 2 h (45% reduction) prior to lye treatment. Stone olives had 21–26% higher acrylamide levels than pitted olives and 42–50% higher levels than sliced olives in the three studied varieties. When calcium chloride (CaCl₂) was added to the brine and brine sodium chloride (NaCl) increased from 2% to 4%, olives presented higher concentrations of this contaminant. The addition of additives did not affect acrylamide levels when olives were canned without brine. Results from this study are very useful for the table olive industry to identify critical points in the production of Californian-style green ripe olives, thus, helping to control acrylamide formation in this foodstuff.