NaOH-free debittering of table olives using power ultrasound

Biodiesel production enhanced by ultrasound-assisted esterification and transesterification of inedible olive oil

In the first phase of this study, inedible olive oil with different initial free fatty acid concentrations (2.5, 5.0, and 10.0%) was processed through acid-catalyzed esterification. Various heating methods were used for this purpose. The ultrasound-assisted esterification and traditional magnetic stirrer-assisted esterification methods were similar to each other in terms of their effects on free fatty acid reduction. However, the ultrasound reaction time was significantly shorter than that of the traditional magnetic stirrer. In the second phase of this study, biodiesel production was carried out through the ultrasound-assisted transesterification of inedible olive oil. Independent variables were, namely, ultrasound power level (30, 90, and 150 W), methanol/oil mole ratio (3, 9, and 15), catalyst concentration (0.5, 1.0, and 1.5%), ultrasound time (15, 30, and 45 min), and reaction temperature (45, 55, and 65 °C), which affected the yield indices and physicochemical constants of the produced biodiesel. The purest biodiesel (98.95%) and the highest amount of yield (92.69%) were observed when using an ultrasound power level of 90 W, a methanol/oil mole ratio of 9, a catalyst concentration of 1.0%, an ultrasound time of 30 min, and a reaction temperature of 55 °C. Optimizing the reaction conditions of the ultrasound operation can effectively increase the biodiesel yield (92.69%), while reducing the energy consumption (4.775 kWh/kg) and shortening the reaction time (30 min), compared to the traditional magnetic stirrer (77.28%, 2.17 kWh/kg, and 120 min, respectively). Therefore, ultrasound-assisted transesterification can serve as an effective alternative because of its fast and economic operation for making biodiesel out of inedible olive oil.

Current Status, Recent Advances, and Main Challenges on Table Olive Fermentation: The Present Meets the Future

Table olives are among the most well-known fermented foods, being a vital part of the Mediterranean pyramid diet. They constitute a noteworthy economic factor for the producing countries since both their production and consumption are exponentially increasing year by year, worldwide. Despite its significance, olive’s processing is still craft based, not changed since antiquity, leading to the production of an unstable final product with potential risk concerns, especially related to deterioration. However, based on industrial needs and market demands for reproducible, safe, and healthy products, the modernization of olive fermentation processing is the most important challenge of the current decade. In this sense, the reduction of sodium content and more importantly the use of suitable starter cultures, exhibiting both technological and potential probiotic features, to drive the process may extremely contribute to this need. Prior, to achieve in this effort, the full understanding of table olive microbial ecology during fermentation, including an in-depth determination of microbiota presence and/or dominance and its functionality (genes responsible for metabolite production) that shape the sensorial characteristics of the final product, is a pre-requisite. The advent of meta-omics technology could provide a thorough study of this complex ecosystem, opening in parallel new insights in the field, such as the concept of microbial terroir. Herein, we provide an updated overview in the field of olive fermentation, pointing out some important challenges/perspectives that could be the key to the olive sector’s advancement and modernization.

Improving biodiesel yield from pre-esterified inedible olive oil using microwave-assisted transesterification method

In the present research, biodiesel production from olive oils with different initial free fatty acid concentrations (2.5, 5.0, and 10.0%) was evaluated. A two-stage acid-catalyzed esterification and alkaline-catalyzed transesterification (ACT) process using the microwave heating method was compared with the traditional heating method. Free fatty acid was reduced to less than 2.0% in the first stage. Although no significant difference was observed between microwave and traditional esterification methods in terms of fatty acid reduction, the microwave treatment significantly decreased reaction time by 92.5%. Comparing microwave ACT results with those of the traditional heating method showed that the microwave can significantly increase methyl ester yield and purity, and simultaneously decrease reaction time. Physical constants of methyl esters were also improved using the microwave heating method. Therefore, the microwave heating method can be regarded as an efficient method instead of the two-stage method for biodiesel production. This method is capable of using inedible olive oil with high concentrations of free fatty acids.

Reduction of bitterness in green walnuts by conventional and ultrasound-assisted maceration

The efficiency of conventional and ultrasound-assisted maceration was investigated in comparison to reduce the bitterness of green walnuts. Conventional maceration was studied at room temperature for 6, 8 and 10 days while ultrasound-assisted maceration (20 kHz, %100 of amplitude) was performed at 36 °C for 6, 8, 10, 12, and 14 h. Phenolic content and antioxidant activity of green walnuts were decreased by reduction of bitterness. Phenolic content and antioxidant activity of green walnut jams prepared from debittered green walnuts by ultrasound-assisted maceration were higher than those of conventional maceration excluding ellagic acid only. Based on findings of sensory analyses, bitterness level was similar in green walnut jams prepared by ultrasound-assisted maceration for 12 h and conventional maceration for 6 days. On the other hand, green walnut jams processed by ultrasound-assisted maceration for 12 h led to the highest general acceptance. It was concluded that ultrasound-assisted maceration may provide better nutritional and sensory quality in green walnut jam. In addition, the time required for reduction of bitterness may be shortened from days to hours by ultrasound-assisted maceration.

Table Olives: An Overview on Effects of Processing on Nutritional and Sensory Quality

Table olives are a pickled food product obtained by a partial/total debittering and subsequent fermentation of drupes. Their peculiar sensory properties have led to a their widespread use, especially in Europe, as an appetizer or an ingredient for culinary use. The most relevant literature of the last twenty years has been analyzed in this review with the aim of giving an up-to-date overview of the processing and storage effects on the nutritional and sensory properties of table olives. Analysis of the literature has revealed that the nutritional properties of table olives are mainly influenced by the processing method used, even if preharvest-factors such as irrigation and fruit ripening stage may have a certain weight. Data revealed that the nutritional value of table olives depends mostly on the balanced profile of polyunsaturated and monounsaturated fatty acids and the contents of health-promoting phenolic compounds, which are best retained in natural table olives. Studies on the use of low salt brines and of selected starter cultures have shown the possibility of producing table olives with an improved nutritional profile. Sensory characteristics are mostly process-dependent, and a relevant contribute is achieved by starters, not only for reducing the bitterness of fruits, but also for imparting new and typical taste to table olives. Findings reported in this review confirm, in conclusion, that table olives surely constitute an important food source for their balanced nutritional profile and unique sensory characteristics.

Two Nonthermal Technologies for Food Safety and Quality-Ultrasound and High Pressure Homogenization: Effects on Microorganisms, Advances, and Possibilities: A Review

Some nonthermal technologies have gained special interest as alternative approaches to thermal treatments. High pressure homogenization (HPH) and ultrasound (US) are two of the most promising approaches. They rely upon two different modes of action, although they share some mechanisms or ways of actions (mechanic burden against cells, cavitation and micronization, primary targets being the cell wall and the membrane, temperature and pressure playing important roles for their antimicrobial potential, and their effect on cells can be either positive or negative). HPH is generally used in milk and dairy products to break lipid micelles, whereas US is used for mixing and/or to obtain active compounds of food. HPH and US have been tested on pathogens and spoilers with different effects; thus, the main goal of this article is to describe how US and HPH act on biological systems, with a focus on antimicrobial activity, mode of action, positive effects, and equipment. The article is composed of three main parts: (i) an overview of US and HPH, with a focus on some results covered by other reviews (mode of action toward microorganisms and effect on enzymes) and some new data (positive effect and modulation of metabolism); (ii) a tentative approach for a comparative resistance of microorganisms; and (iii) future perspectives.

The phytochemical rich potential of acorn (Quercus aegilops) products and by products

The phytochemical content of acorn (Quercus aegilops) products (nuts and flour) and by products (shells and leaching waters) regarding their content in total phenols, fatty acids, sodium, potassium and calcium was investigated. Antioxidant activity was also examined. Acorn materials presented high total phenol content (up to 47.6 ± 0.6 mg gallic acid equivalents (GAE)/g dry material), with a substantial amount remaining after leaching (11.6 ± 0.7 mg GAE/g flour), and high DPPH radical scavenging and ferric reducing activity. Their content in potassium, calcium, oleic and linoleic acids was considered significant. Molecular weight distribution of proteins and peptides was also studied and found between 7 and 45 kDa; only for acorn shells a band > 250 kDa appeared. Leaching parameters (time, material size, material to water ratio, temperature, NaCl presence) significantly affected the phytochemical content of the remained leached material.

Technologies and Trends to Improve Table Olive Quality and Safety

Table olives are the most widely consumed fermented food in the Mediterranean countries. Peculiar processing technologies are used to process olives, which are aimed at the debittering of the fruits and improvement of their sensory characteristics, ensuring safety of consumption at the same time. Processors demand for novel techniques to improve industrial performances, while consumers' attention for natural and healthy foods has increased in recent years. From field to table, new techniques have been developed to decrease microbial load of potential spoilage microorganisms, improve fermentation kinetics and ensure safety of consumption of the packed products. This review article depicts current technologies and recent advances in the processing technology of table olives. Attention has been paid on pre processing technologies, some of which are still under-researched, expecially physical techniques, such ad ionizing radiations, ultrasounds and electrolyzed water solutions, which are interesting also to ensure pesticide decontamination. The selections and use of starter cultures have been extensively reviewed, particularly the characterization of Lactic Acid Bacteria and Yeasts to fasten and safely drive the fermentation process. The selection and use of probiotic strains to address the request for functional foods has been reported, along with salt reduction strategies to address health concerns, associated with table olives consumption. In this respect, probiotics enriched table olives and strategies to reduce sodium intake are the main topics discussed. New processing technologies and post packaging interventions to extend the shelf life are illustrated, and main findings in modified atmosphere packaging, high pressure processing and biopreservaton applied to table olive, are reported and discussed.

Improving oxidative stability of virgin olive oil by addition of microalga Chlorella vulgaris biomass

Antioxidant activity of Chlorella (Chlorella vulgaris) was evaluated in virgin olive oil (VOO) at different concentrations of 0.5, 1.0, and 1.5% (w/w) under accelerated storage conditions. Antioxidant activity of Chlorella was compared with those of BHT and β-carotene. Chlorella samples significantly retarded the formation of primary, secondary, and total oxidation products in comparison with those of the control. The stability increased as concentrations of Chlorella increased. Samples containing 0.5, 1.0, and 1.5% Chlorella significantly improved VOO stability by 19.99, 28.83, and 33.14%, respectively. Observed effects can be related to the release in the assortment of bioactive compounds from Chlorella algae to the VOO. Among the different antioxidants evaluatedy, BHT exhibited the highest antioxidant activity. On the contrary, β-carotene had no preventive effect against the oxidation of VOO. It also proved incapable of limiting the progress of VOO oxidation and played role as pro-oxidant. In conclusion, Chlorella enhanced VOO oxidative stability. Thus it can be considered as a promising source of natural antioxidants.