Asiye Akyıldız

Comparison of phenolic compounds of orange juice processed by pulsed electric fields (PEF) and conventional thermal pasteurisation

Processing of orange juice by pulsed electric fields (PEF) and thermal pasteurisation was carried out to compare changes in total phenolic concentration, hydroxybenzoic acid, hydroxycinnamic acids, flavonols, flavones and flavonones before and after being stored at 4°C for 180days. Changes in the initial total phenolic concentration of the samples varied depending on the applied electric field intensity and thermal pasteurisation. Hesperidin and chlorogenic acids were detected as the most abounded flavonoid and phenolic acids in the orange juice, respectively. Except for syringic acid and neoeriocitrin, the concentration of the phenolic compounds indentified in the orange juice samples enhanced after the PEF or thermal pasteurisation. The samples treated with PEF had more stable flavonoids and phenolic acids than those treated with the thermal pasteurisation. The PEF-treated samples had higher sensory scores than the heat-treated samples.

Effects of PEF and heat pasteurization on PME activity in orange juice with regard to a new inactivation kinetic model

The inactivation kinetics of pectin methyl esterase (PME) during the shelf life (4°C-180 days) of freshly squeezed orange juice samples processed by both pulsed electric fields (PEF) and heat pasteurization (HP) was evaluated in the study. The PME inactivation level after the PEF (25.26 kV/cm-1206.2 μs) and HP (90°C-20s) treatments were 93.8% and 95.2%, respectively. The PME activity of PEF-processed samples decreased or did not change, while that of HP samples increased during storage (p<0.01). A kinetic model was developed expressing PME inactivation as a function of the PEF treatment conditions, and this enabled the estimation of the reaction rate constant (587.8-2375.4s(-1)), and the time required for a 90% reduction (De, 3917.7-969.5s). Quantification of the increase in PEF energy to ensure a ten-fold reduction in De (ze, 63.7 J), activation electric fields (-921.2 kV cm(-1)mol(-1)), and electrical activation energy (12.9 kJ mol(-1)) was also carried out. Consequently, PEF processing was very effective for the inactivation of PME and for providing stability of orange juice during storage.

Effects of Different Enzymes and Concentrations in the Production of Clarified Lemon Juice

Lemon juice obtained from Interdonato variety was treated with different enzymes at specific concentrations as depectinization processes to produce clear lemon juice and its concentrates. In addition, the best condition obtained from laboratory treatments was carried out in the local fruit juice plant. Effects of the processing steps on some quality parameters were investigated during the lemon juice production and the obtained concentrates were stored at −25°C for 180 days. The results showed that Novozym 33095 had the best depectinization effectiveness. Total pectin content of lemon juices decreased rapidly following the enzyme treatment and could not be detected following the filtration. Viscosity values decreased after pulp separation and the largest reduction was observed with the filtration. At the end of filtration in 40 μL/100 mL concentrations of each of the three enzymes, values of residual pectinmethylesterase (PME) activity were found to be in the lowest amounts.

Citrus Juices Technology

Citrus fruits are widely grown throughout the world and contain various bioactive compounds with antioxidant activities including vitamin C, carotenoids, and phenolic compounds. These components are very important for human health and provide protection against harmful free radicals. Citrus fruits are mostly consumed as fresh fruits or fruit juices. To obtain high quality and safe citrus juice, certain critical points (oil extraction from peel, juice extraction, pulp removing, pasteurization, evaporation, and aseptic filling) need to be taken into consideration during citrus juice processing. Firstly, oil extraction from the peel is a necessary step to limit the level of peel oil components in the juice. Secondly, selected juice extraction techniques and process conditions are very important for the yield and total quality of the juice. Thirdly, the pulp removal is an important step to remove most of pectinmethylesterase (PME) and its heat resistance isoenzymes. Further inactivation of remaining PME enzymes and pathogenic or spoilage microorganisms is also obtained with the pasteurization step. Finally, equipment used for the juice production and the concentration conditions have various effects on the sensory properties of the citrus juices. As a result, minimal processing would be applied to citrus juices if the processing steps detailed above are optimized. Obtaining clarified citrus juices from the citruses which have lower carotenoid content including lemon and lime juice is a new trend these days. It is needed to be focused on enzymation (depectinization), clarification assistance agents, and filtration conditions during the clarified juices production. Citrus peel (flavedo) and layer of albedo are the main byproducts of the citrus juice industry. Citrus peel oil is obtained from flavedo layer which has a significant commercial value. Recently, promising nonthermal food preservation technologies were developed including pulsed electric fields (PEF), high pressure processing (HPP), and ultrasonication process (US). These technologies are highly appreciated for their ability to extend the shelf life of food products without the application of heat, thus also preserving the quality attributes such as sensory quality and nutritional value, as well as controlling the microbiological safety of food products.

A Study on the Quality Criteria of Some Mandarin Varieties and Their Suitability for Juice Processing

In this study, some composition properties of juices of different mandarin varieties (Robinson (R), Fremont (F), and Satsuma (S)) were determined before and after pasteurisation. , , , and values of all varieties were increased after the pasteurisation process. Degradation of ascorbic acid was calculated as 2.20, 16.86, and 24.31% for R, F, and S samples, respectively, after pasteurisation. The highest total carotenoid and phenolic contents were determined in S samples. In general, after the pasteurisation treatment, the total carotenoid content of juices was increased slightly, but total phenolic contents were dramatically decreased. The antioxidant activity of pasteurised samples was increased by approximately 6%. The most abundant carotenoid and flavanone glycoside compound was shown to be β-cryptoxanthin and hesperidin, respectively, in all samples. The most popular fresh and pasteurised juice samples were made from the Robinson variety of mandarin with regard to taste, smell, and general impression.

Thermal Pasteurization and Microbial Inactivation of Fruit Juices

Abstract Fruit juices are the most consumed beverages worldwide owing to their rich, natural, healthy nutrients. In the last decade, foodborne disease outbreaks or spoilage problems have been reported for fruit juices consumed especially without thermal pasteurization. Generally, thermal pasteurization of fruit juices is related to heat treatments which are between 60°C and 100°C to destroy target microorganisms or enzymes. In order to produce safe fruit juice that is free of pathogens, is of high quality, meets consumer expectations, and minimizes commercial losses, thermal pasteurization must be effective. To achieve this, the physicochemical properties of fruit juices (such as pH), inactivation mechanisms of target microorganisms and enzymes, enzymatic and microbiologic backgrounds of fruit juices, and finally, engineering aspects of thermal pasteurization must be taken into consideration all together. This chapter attempts to put forward these perspectives to obtain summarized practical information and guidelines for those concerned.

Optimization of thermosonication conditions for cloudy strawberry nectar with using of critical quality parameters

The optimum thermosonication parameters, temperature and ultrasound energy density (UED), determined by using response surface methodology to inactivate polyphenol oxidase (PPO) and protecting the quality parameters, especially color of strawberry nectar. The PPO inactivation was successfully achieved by thermosonication treatment. Increasing of temperature resulted with decreasing of browning index and increasing of hydroxymethyl furfural. High temperature-low UED combination can be applied to obtain minimum change in ΔE∗ and maximum protection of ascorbic acid. Thermosonication at mild temperature (∼50 °C) and UED (∼230 J/g) ensured the maximum levels of total monomeric anthocyanin and total phenolic content. The combination of 59 °C and 455 J/g was the conditions of optimum thermosonication to minimize quality parameters which cause undesirable changes like color degradation in nectar and maximize desirable ones which have beneficial effects on characteristics of nectar or on human health like phenolic content of nectar.

Nanoteknolojik Tekniklerle Karotenoid Bileşenlerin Enkapsülasyonundaki Son Gelişmeler

Gida ve saglik endustrisi acisindan karotenoid bilesenler onemli bir potansiyele sahiptir. Karotenoid bilesenler islem ve depolama kosullarina bagli olarak cevresel kosullarin etkisiyle oksidasyona ve izomerasyona ugramaktadir. Ayrica, sindirim sirasinda gida matriksinden tam olarak serbest kalamamasi, parcalanmasi ve hidrofobik ozellikte olmasi biyoyararliligini da azaltmaktadir. Enkapsulasyon, istenmeyen cevresel kosullara karsi koruyucu fiziksel bir bariyer olusturarak biyoaktif bilesenleri uygun kaplama materyalleri ile kaplanmasini saglayan etkili bir islem olarak tanimlanmaktadir. Son yillarda karotenoidlerin dayanimini, islenmesini ve biyoyararligini gelistirmek icin nanoteknolojinin gelismesiyle beraber nanoenkapsulasyon teknolojisinin kullanimi giderek artmaktadir. Yapilan calismalar, nanoenkapsulasyonun, mikroenkapsulasyona gore daha fazla yuzey alani saglamasi, yuksek enkapsulasyon etkinligi ve verimi, suda cozunurlugu arttirmasi ve kontrollu salinimi gelistirmesi gibi ozelliklere sahip olma potansiyelinin yuksek oldugunu gostermektedir. Bu derlemede, karotenoid bilesenlerin dayanimini arttirmak amaciyla kullanilan nanoenkapsulasyon tekniklerinin etkinligi ve bu alandaki son gelismeler uzerinde durulmustur.

Some biochemical characteristics of grafted watermelon

Grafting is an alternative approach to reduce crop damage resulting from soil-borne pathogens. This approach also increases plant abiotic stress tolerance, which in turn increases crop yield and quality. Therefore, the objective of this study was to determine the effect of grafting on watermelon quality parameters with the use of different rootstock combinations. Different morphological characteristics (yellow-red fleshed, with seed-seedless, striped rind and dark green rind) were grafted on rootstocks of Argentario (Lagenaria spp.) and Maximus (Cucurbita maxima × C. moschata). While the highest fructose, sucrose and soluble solids content were measured in Argentario/TP84, TP84 had the highest glucose content. Total carotenoids content in watermelons ranged from 15.36 ± 2.78 to 104.51 ± 12.04 mg kg−1. Argentario/TP84 showed the highest level of lycopene (93.95 mg kg−1) among cultivars and combinations. β-carotene content varied from 1.44 ± 0.01 to 3.76 ± 0.01 mg kg−1. The highest ascorbic acid content was in Argentario/TP84 (17.26 mg kg−1), followed by Argentario/5299 (17.26 mg kg−1). Grafting significantly increased soluble solids, sugars (fructose, glucose and sucrose), total carotenoids and ascorbic acid contents. Maximus/Ant09 had the highest total carotenoids and lycopene content but lowest fructose, sucrose and soluble solids content on C. maxima × C. moschata combinations, whereas Argentario/TP84 has the highest fructose, sucrose, soluble solids, total carotenoids, β-carotene, lycopene and ascorbic acid contents among cultivars and combinations. This study showed that use of bottle gourd (Lagenaria spp.) rootstock could enhance soluble solids, fructose, sucrose, lycopene and ascorbic acid contents in watermelon.