The Influence of pH and Sodium Hydroxide Exposure Time on Glucosamine and Acrylamide Levels in California‐Style Black Ripe Olives

Acrylic acid, N‐acetyl‐glucosamine and glucosamine were investigated for their role in the formation of acrylamide in California‐style black ripe olives [CBROs]. Levels of acrylic acid and glucosamine are reported for the first time in fresh (333.50 ± 21.88 and 243.59 ± 10.06 nmol/g, respectively) and in brine‐stored olives (184.50 ± 6.02 and 165.88 ± 11.51 nmol/g, respectively). Acrylamide levels significantly increased when acrylic acid (35.2%), N‐acetyl‐glucosamine (29.9%), and glucosamine (124.0%) were added to olives prior to sterilization. However, isotope studies indicate these compounds do not contribute carbon and/or nitrogen atoms to acrylamide. The base‐catalyzed degradation of glucosamine is demonstrated in olive pulp and a strong correlation (r² = 0.9513) between glucosamine in olives before sterilization and acrylamide formed in processed CBROs is observed. Treatment with sodium hydroxide (pH > 12) significantly reduces acrylamide levels over 1 to 5 d without impacting olive fruit texture.     

Influence of the type of calcium salt on the cation absorption and firmness of black ripe olives

The preservation of olives intended for processing as black ripe olives must be done in a salt-free environment although it involves the use of calcium addition to retard olive softening. Calcium chloride and calcium lactate were added by up to 1600 mg Ca L⁻¹ (i) in the preservation liquid of olives before darkening and (ii) in the cover packing brine. The highest texture and calcium absorption were found in the latter case. In addition, the sensory characteristics of the final product were not affected by the use of any of the calcium salts studied at concentrations of up to 1600 mg Ca L⁻¹. Calcium chloride and calcium lactate can be employed to obtain higher texture and calcium content in black ripe olives, although it is advisable to add the cation to the cover packing brine of pitted olives rather than to the preservation liquid.     

Optimization of Ripe Olive Processing with a Single Lye Treatment

The development of a method for darkening black ripe olives during the washing step with a single NaOH treatment and preservation liquid was studied. Olives of the Hojiblanca cultivar were darkened at pilot plant scale, packed, sterilized, and analyzed after 2 mo of storage at ambient temperature. It was found that the use of a mixture of preservation liquid:water at a ratio of 1:1 during the first washing gave rise to darker olives with slightly better firmness and no effect on sensory quality. However, care must be taken with the concentration of acetic acid in the preservation solution, as a content of this organic acid higher than 25 g/L can cause adverse effects on olive color due to the low pH that can be reached in the flesh of the fruit. Additionally, the re‐use of the preservation solution in the first washing resulted in enrichment in antioxidant compounds of the packed product. Black ripe olives processed with preservation liquid had a total phenolic content of 629 mg/kg, whereas those with only tap water had 376 mg/kg, in particular hydroxytyrosol and hydroxytyrosol‐4‐glucoside. These findings mean that it is possible to get darker olives with higher contents in bioactive substances by reusing the preservation liquid during the darkening step of black ripe olives.     

Effect of amino acids on the chemical oxidation of olive o-diphenols in model systems

Addition of certain amino acids (l-tryptophan, l-histidine, l-cysteine and l-cystine) to model solutions of caffeic acid and hydroxytyrosol (the two most characteristic o-diphenols of ripe olives) improved the dark colour obtained after oxidation. A detailed study carried out with l-cysteine and caffeic acid showed that, after an initial inhibitory effect, increasing concentrations of amino acid led to darker solutions. The same effect was also found in hydroxytyrosol solutions with increasing amounts (2–8 mm) of cysteine without lag phase, except for 10 mm level. Cysteine also produced darker colour with oxidised storage brine of ripe olives. These results open the door to a possible use of this amino acid as additive or aid in processing to produce darker and homogeneous ripe olives.     

Effect of processing techniques on antioxidative enzyme activities, antioxidant capacity, phenolic compounds, and fatty acids of table olives

In this study, olive fruits (Olea europeae cv. Gemlik) of the most common sources of table olives in Turkey were used. Total polyphenol content (TPC), antioxidant capacity (AC), and antioxidant enzymes (catalase, CAT; ascorbate peroxidase, APX; and glutathione reductase, GR) of table olives were compared by 4 different methods of ripe table olive processing. Results revealed that TPC of the processed olives ranged from 117.44 to 418.69 mg gallic acid equivalents/g fresh weight (f.w.). The highest AC as mg Trolox equivalents of 189.58/g f.w. was obtained from unprocessed black olives. CAT, APX, and GR activities of unprocessed olives were higher than those obtained in all processed olives. In conclusion, TPC, AC, and antioxidant enzyme activities are strongly affected by fruit ripening and processing in table olives of ‘Gemlik’ cultivar. In addition, the best processing technique is untreated black olives in brine for antioxidant properties.     

Absorption of sorbic and benzoic acids in the flesh of table olives

The distribution of sorbic and benzoic acids in the different phases of table olives was studied. To a large extent, these preservatives accumulated in the oil phase of fruits stored in acid conditions, as well as in juice and other tissue components. Thus, around 20–30% of the benzoic acid in olives was found in the juice phase, 30–50% in the oil phase and 30–40% in the rest of the olive flesh. Experiments carried out with black ripe olives revealed that an increase in pH of the medium gave rise to a decrease in the absorption phenomenon in whole olives and in the oil phase. As a consequence of this effect, benzoic acid could be leached from stored black ripe olives during the darkening process, although the calcium content of fruits greatly influenced the diffusion phenomenon. The results obtained in this study are important for future legal limitations of these preservatives in table olives and inhibition capacity of them in commercial table olives.     

Olive Fermentation and Processing: Scientific and Technological Challenges

ABSTRACT: The 3 main commercial table olive preparations are the Spanish-style green olives, the Greek-style naturally black olives, and the Californian-style black ripe olives. In all cases, fruits undergo fermentation in brine solution, which preserves them and increases palatability. Lactic acid bacteria dominate in brines of green olives, while mainly fermentative yeasts are found in brines of black ones. The fermentation is spontaneous and begins as soon as olives are put into brine. Research on table olives has been going on for 100 years, but many questions remain. Previous work has focused on the efficient utilization of starter cultures in order to control the fermentation, to guarantee the absence of spoilage, and to govern the relationship between olive flavor and microorganisms. Nowadays, there is concern over environmental problems that the fermentation solutions represent, in particular their high NaCl content. Fermentation or simply storing olives in water without salt presents some problems. The high concentration of sodium benzoate used for storing black ripe olives by the American industries is not advisable for European processes due to the residual amount of preservative in the final product. Fermentation of green olive wash waters, in order to obtain valuable products, is being pursued, but polymeric inhibitors are problematic and undesirable microorganisms grow. The consumption of organic foods is increasing and black olives fit the definition since they are processed without chemical treatment. However, the hydrolysis of the bitter compound oleuropein, either by microorganisms or acids, needs to be studied.     

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 (<10,000 Da), 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.     

Profile of anti-lactic acid bacteria compounds during the storage of olives which are not treated with alkali

The objectives of this study were: (1) to characterize the phenolic and oleosidic compounds in the preservation solutions of black ripe olives, particularly those with antimicrobial activity and (2) to explain the growth of lactic acid bacteria (LAB) in the olive brines. Fruits were put into industrial tanks and preserved in acidified solutions under aerobic or anaerobic conditions. Lactic acid was analyzed as a marker of LAB growth in the olive brines. Hydroxytyrosol was the most concentrated phenolic compound in these solutions followed by hydroxytyrosol 4-glucoside, hydroxytyrosol 1-glucoside, tyrosol and salidroside. Among the oleosidic compounds, secoxyloganin and oleoside 11-methyl ester were found in a concentration between 0.3 and 3 mM, whereas secologanoside and oleoside were always detected at a concentration below 0.2 mM. Likewise, a notable concentration of the dialdehydic form of decarboxymethyl elenolic acid either free or linked to hydroxytyrosol was found at the beginning of preservation, which was high enough to inhibit LAB growth. However, an acidic degradation of these antimicrobials occurred with time, particularly in the summer, and it allowed for the growth of lactobacilli and the formation of lactic acid. The results of this study are a contribution to explain the microbial fermentation in acidified solutions of olives which are not treated with NaOH on an industrial scale.     

A study on the implications of NaCl reduction in the fermentation profile of Conservolea natural black olives

This study examined the impact of different mixtures of NaCl, KCl, and CaCl₂ on the fermentation profiles of Conservolea natural black olives. Five different combinations of chloride salts were investigated, namely (i) 8% NaCl (control treatment), (ii) 4% NaCl and 4% KCl, (iii) 4% NaCl and 4% CaCl₂, (iv) 4% KCl and 4% CaCl₂, and (v) 2.6% NaCl-2.6% KCl-2.6% CaCl₂. The changes in the microbial association (lactic acid bacteria, yeasts, Enterobacteriaceae), pH, titratable acidity, organic acids, volatile compounds, and mineral content in olive flesh were analyzed. Results demonstrated that all salt combinations led to vigorous lactic acid processes based on the obtained values of pH (3.9-4.2) and titratable acidity (0.70-0.86 g lactic acid per 100 ml brine). Organoleptic evaluation was a critical factor in the acceptability of the final product. Increasing concentrations of CaCl₂ or a combination of KCl and CaCl₂ rendered the product bitter with low acceptability by the taste panel. Only one combination of chloride salts (4% NaCl and 4% KCl) could finally produce olives with lower sodium content and good organoleptic attributes. The results of this study could be employed by the Greek table olive industry in an attempt to produce natural black olives with less sodium without affecting the traditional taste of fermented olives in order to meet consumers’ demand for low sodium dietary intake.     

Olive glutaraldehyde-like compounds against plant pathogenic bacteria and fungi

Aqueous solutions from table olives constitute a major environmental problem because of their high mineral and organic contamination but they also contain compounds with antimicrobial properties. In this study, the bactericidal and fungicidal activities of salt-free table olive solutions against several phytopathogenic micro-organisms were examined. The storage solutions of black ripe olives showed noticeable bactericidal activity against species of Erwinia, Clavibacter, Agrobacterium and Pseudomonas, although the washing waters from Spanish-style green olives were less effective. In fact, black olive storage solutions diluted to 20–30% were able to reduce the inoculated population of Erwinia amylovora and Pseudomonas syringae up to 6–7 log. This bactericidal activity was correlated with the presence of olive glutaraldehyde-like compounds such as the dialdehydic form of decarboxymethyl elenolic acid in these solutions, either free or linked to hydroxytyrosol. Experiments in vitro demonstrated that the bactericidal activity of these substances could explain most of the activity of the black olive storage solutions. Moreover, these salt-free table olive solutions also showed fungicidal activity against species of Phytophthora, Colletotrichum, Alternaria, Botrytis and Pestalotiopsis. The black olive storage solutions were more fungicidal than the washing solutions from Spanish-style green olives, with mycelial growth inhibition of up to 100% being attained, in some instances. These findings open the possibility of using table olive wastewaters in agriculture for pest management.     

Industrial implementation of black ripe olive storage under acid conditions

Restrictions on the discharge of chloride in wastewater streams have recently increased, and processors of black ripe olives have to look for alternative storage systems to the traditional brines. Ripe olives of the Hojiblanca variety were stored under aerobic and anaerobic conditions in industrial underground tanks for one year. The aerobic systems assayed with or without NaCl produced a continuous consumption of sugars as they diffused from the fruits to the surrounding liquid. At the same time sugars accumulated in the liquid for months when anaerobic conditions were employed and a high concentration of acetic acid was used. In the end, glucose was consumed with time as well and, in addition to yeasts, acetic acid and lactic acid bacteria grew in the cover solutions. The assessment of olives stored under the different systems and processed as black ripe olives revealed that the traditional aerobic brines gave rise to darker and firmer fruits. However, olive industries must eliminate chlorides from their waste streams. Promising new storage systems were (i) anaerobic preservation of olives in water with an initially high concentration of acetic acid, and (ii) aerobic preservation in water with an initially low concentration of acetic acid. Both systems produced a good quality product, free of microbial spoilage and organoleptic defects.     

Influence of fruit ripeness and salt concentration on the microbial processing of Arbequina table olives

Arbequina table olives are processed as “naturally green olives”, they are directly placed in brine and fermentation starts spontaneously. Olives are harvested just before they change to ‘turning colour’. Different salt concentrations are used depending on the producer. The aim of the study was to evaluate how (i) the ripeness of the olive when it is harvested and (ii) the salt concentration of the brine influence the different microorganism populations in brine during the fermentation of Arbequina table olives.The results showed that the Enterobacteriaceae population lasted longer in black and turning colour olives than in green olives, whereas the growth of lactic acid bacteria was delayed in green olives. A higher salt concentration favoured the elimination of Enterobacteriaceae and hindered yeast growth. The main yeast species identified were Pichia anomala, Candida sorbosa and Candida boidinii, while Lactobacillus plantarum was the only lactic acid bacteria species involved in the process. In a sensory test, panellists preferred green olives and were not able to tell the laboratory-scale processed olives from a commercial sample, nor could they distinguish green olives from different brines.     

Reduction of acrylamide formation by selected agents in fried potato crisps on industrial scale

Great interest and rapid research efforts on acrylamide in foods followed an announcement in April 2002 by the Swedish National Food Authority and the University of Stockholm. Reduction of acrylamide in high-temperature processing foods, including selection of the raw material and variation of processing parameters, etc. were extensive reported. In this research, effect of some agents on acrylamide formation was investigated. A glucose-asparagines reaction model system was used to test the effect of ferulic acid, catechin, CaCl₂, NaHSO₃, and l-cysteine on inhibition of acrylamide formation and three efficient inhibitors, NaHSO₃, CaCl₂ and l-cysteine were screened. The results showed that immersing of the fresh potato chips using different concentration of the agents greatly inhibited acrylamide formation in fried potato crisps, and the efficiency increased as their concentrations increased; among them, l-cysteine is the most efficient agent but CaCl₂ is most potential. Effects of these food additives on the texture of fried potato crisps were also studied. It was found that l-cysteine showed little effect on the texture of the crisps and CaCl₂ is regarded as the suitable choice because of its low price and the acceptable mouth feel of fried crisps treated by CaCl₂, although it increased the brittleness. Moreover, the application of CaCl₂ in industrial production of fried potato crisps was also studied. In the blanching process (deactivation process of enzymes at 85 °C), a computerized electrical conductivity detector was used to keep the concentration of CaCl₂ at constant and the result showed that immersion of potato slices in CaCl₂ solution at 5 g/L reduced acrylamide formation by more than 85% in fried crisps.Industrial relevanceThis research presents a technology to inhibit acrylamide formation in fried potato chips by immersion of fresh potato chips with some food additives. The approach suggested that cysteine and calcium chloride significantly decreased the content of acrylamide in fried potato chips and their concentrations could be kept constant by using a conductor as a detector.     

Effect of ripening stage and infusion with calcium lactate and sucrose on the quality and microstructure of frozen mango

The effect of the ripening stage and infusion with calcium lactate and sucrose on the quality and microstructure of frozen mango was investigated. Partially ripe and ripe mangoes cubes were infused in 1% calcium lactate solution or a combination of 1% calcium lactate and 50% sucrose solution for 1 h before freezing at ?20 °C and stored for 14 days. After thawing, both the partially ripe and ripe mangoes treated with the combination of calcium lactate and sucrose exhibited the highest firmness value, sensory firmness score and lowest drip loss. Light microscope images also illustrated less damage to the cell wall of mango pretreated with calcium and sucrose. The calcium‐reinforced structure of the fruit and osmotic dehydration with sucrose reduced the freezable water content and consequently limited ice crystal damage. Furthermore, partially ripe mango was more suitable for freezing than ripe mango due to its stronger cell wall structure.     

Recycling preservation solutions in black ripe olive processing

The purpose of this study was to evaluate the reuse of the liquid employed to preserve black ripe olives in a new fermentation process. The fermentation of olives in these reused solutions (ozonated, acetic acid distillate and old storage solutions) produced similar results as with a fresh acetic acid solution. The pH was between 3.8 and 4.1, and the free acidity ranged from 1.4 to 2.6. Yeasts and acetic acid bacteria were the predominant microorganisms, while lactic acid bacteria grew occasionally after 6–8 months of storage. Off‐odours, fruit defects or any other spoilage were not detected in any case. Moreover, the quality of the darkened product (colour, firmness, flavour) was statistically similar for all treatments, although fruits preserved in a reused ozonated liquid showed less dark fruits (R₇₀₀ = 9.7–10.7) than the others (R₇₀₀ = 7.7–9.3). These results open the possibility of reusing the black olive solutions in a new preservation process.     

Physicochemical Properties,and Antioxidant and Antimicrobial Effects of Garlic and Onion Powder in Fresh Pork Belly and Loin during Refrigerated Storage

ABSTRACT: Pork loin and belly cuts were pumped to 110% of their original weight with solutions containing 5% of various ingredients (sodium ascorbate, garlic, and onion powder), and evaluated the physicochemical properties, and antioxidant and antimicrobial activities during refrigerated storage at 8 °C. The addition of garlic and onion powder tended to increase redness (a) and yellowness (b) in both the belly lean and loin with the exception of a few cases. Free fatty acid values in both pork belly and loin cuts were reduced with the addition of these ingredients, as compared to the control. Significant differences in peroxide values were observed in sodium ascorbate and garlic‐injected belly, and in sodium ascorbate and onion‐injected loin, as compared to the control. Thiobarbituric acid reactive substance values in the pork belly with garlic or onion powder were significantly lower than in the belly without these ingredients or with sodium ascorbate (P < 0.05). Total plate counts were lower in both the belly and loin containing garlic and onion powder, as compared to the control. In both the belly and loin cuts, the content of oxidative products (volatile compounds) was reduced with the addition of garlic and onion powder, particularly the aldehydes (hexanal). Overall, garlic and onion in enhanced meats showed an antioxidant activity as effective as that of sodium ascorbate and also an antimicrobial effect to inhibit the growth of total bacteria and Enterobacteriaceae.     

High pressure processing of garlic paste: effect on the quality attributes

The effect of high pressure treatment and conventional thermal processing on the various quality attributes of garlic paste was evaluated in terms of physicochemical, enzymatic, sensory and microbiological parameters. Thermal treatment inactivated the polyphenol oxidase and peroxidase enzymes, whereas an enhanced activity was noted at 200 MPa which reduced significantly (P < 0.05) when treated with 400 and 600 MPa. Total phenolics, flavonoids and antioxidant activities showed an increasing trend with increase in pressure, whereas thermal processing was found to significantly (P < 0.05) decrease these phytocompounds. The CIE (L*, a*, b*) values were found to be better retained in high pressure‐processed pastes compared with thermally treated one. The microbial counts in terms of total plate count, yeast and mould count as well as total coliform counts were reduced significantly (P < 0.05) in both the treatments. Sensory attributes were found to be better in the case of high pressure‐processed samples as compared to the thermally treated one.     

Spanish‐style green table olive shelf‐life

Changes in the physicochemical and sensory characteristics of commercial whole, pitted and stuffed with pepper, garlic or anchovy paste Spanish‐style green table olives of the Gordal, Manzanilla and Hojiblanca cultivars were studied during a three‐year period. No olives developed any spoilage during this period, and at the end of it, all presentations were classified as ‘extra’ according to the sensory evaluation methodology issued by the International Olive Council. Throughout the shelf‐life, surface colour index and firmness of the olives degraded in accordance with a first‐order kinetics, while a gradual browning of the cover brines was observed; however, products added with ascorbic acid maintained a stable colour, while those with calcium content showed reduced firmness degradation. No significant changes in most of the sensory characteristics were observed by the panel test during shelf‐life and only slight changes in firmness, and surface colour were noticed in samples with significant differences in these attributes when measured instrumentally.