Effect of incubation temperature and caseinates on the rheological behaviour of Kefir

AbstractThe effect of incubation temperature and the addition of caseinates on the rheological behaviour of kefir was studied by using a pneumatic tube viscometer of novel design. The results indicated that the incubation time increased as the incubation temperature was reduced and the casein concentration was increased. Kefir samples incubated at 25°C showed the highest values of viscosity, while the samples incubated at 30°C exhibited the lowest viscosity. The addition of caseinates caused the viscosity of the samples to increase and their flow behaviour index values to decrease. Kefir samples incubated at 30°C exhibited the highest flow behaviour index values

Zamjena masti u trajnim kobasicama emulzijom ekstra djevičanskog maslinovog ulja s dodatkom autohtonih bakterija mliječno-kiselog vrenja

Research background. Formulations based on vegetable or fish oil and modifications in the production technology of dry fermented sausages have emerged in recent years aiming to achieve the desirable target of reducing the fat content of these meat products. However, previous efforts have confronted many difficulties, such as high mass loss and unacceptable appearance due to intensely wrinkled surfaces and case hardening. The objective of this study is to produce and evaluate dry fermented sausages by utilising a meat protein-olive oil emulsion as fat substitute and indigenous lactic acid bacteria (LAB) with probiotic properties isolated from traditional Greek meat products. Experimental approach. A novel formulation with extra virgin olive oil and turkey protein was developed to totally replace the conventionally added pork fat. Probiotic and safety characteristics of autochthonous LAB isolates from spontaneously fermented sausages were evaluated and three LAB isolates were finally selected as starter cultures. Physicochemical, microbiological and sensory analyses were carried out in all treatments (control, Lactobacillus acidophilus, L. casei, L. sakei and Pediococcus pentosaceus) during fermentation. Results and conclusions. Ready-to-eat sausages were found to be microbiologically stable. The olive oil-based formulation produced in this study generated a mosaic pattern visible in the sliced product simulating the fat in conventional fermented sausages and was regarded as an ideal fat substitute for the production of fermented sausages. An autochthonous isolate of Lactobacillus casei adapted the best to the final products as it was molecularly identified to be present in the highest counts among the LAB isolates used as starter cultures. Novelty and scientific contribution. Α novel and high-quality dry fermented meat product was produced by replacing the added pork fat with a fat substitute based on a meat protein-olive oil emulsion. Autochthonous LAB with in vitro probiotic properties could have a potential use in large-scale novel dry fermented sausage production. Such isolates could be used as starters in an effort to standardise the production process and retain the typical organoleptic and sensory characteristics. Moreover, isolates like L. casei 62 that survived in high counts in the final products can increase the safety of fermented sausages by competing not only with pathogens but also with the indigenous microbiota and could have a potential functional value for the consumer.Pozadina istraživanja. Posljednjih godina se u proizvodnji trajnih kobasica koriste novi pripravci na bazi biljnog ili ribljeg ulja koji smanjuju udjel masti u tim mesnim proizvodima. Međutim, dosadašnji napori u dobivanju takvih proizvoda nailazili su na mnoge prepreke, kao što su veliki gubitak mase i neprihvatljiv izgled proizvoda zbog prevelike naboranosti površine i tvrdoće crijeva. Svrha je ovoga rada bila proizvesti trajne kobasice s emulzijom maslinovog ulja i proteina mesa kao zamjenom za masti, uz dodatak autohtonih bakterija mliječno-kiselog vrenja s probiotičkim svojstvima izoliranih iz tradicionalnih grčkih mesnih proizvoda, te ispitati svojstva dobivenih proizvoda. Eksperimentalni pristup. Razvijen je novi pripravak s ekstra djevičanskim maslinovim uljem i proteinima iz puretine koji bi u potpunosti zamijenio tradicionalno dodavanu svinjsku mast. Ispitana su probiotička svojstva i sigurnost primjene autohtonih bakterija mliječno-kiselog vrenja izoliranih iz tradicionalnih fermentiranih kobasica, i izdvojena su tri izolata koja su zatim upotrijebljena kao starter kulture. Tijekom fermentacije provedene su fizikalno-kemijske, mikrobiološke i senzorske analize svih ispitanih uzoraka (kontrolnog uzorka, te kobasica proizvedenih s pomoću Lactobacillus acidophilus, L. casei, L. sakei i Pediococcus pentosaceus). Rezultati i zaključci. Gotovi proizvodi bili su mikrobiološki stabilni. Dodatkom pripravka na bazi maslinovog ulja dobivena je kobasica koja je na presjeku imala mozaičan izgled sličan onom tradicionalne kobasice, pa se pripravak smatra idealnom zamjenom za mast u proizvodnji trajnih kobasica. Molekularnom je analizom utvrđeno da je među bakterijama mliječno-kiselog vrenja koje su korištene kao starter kulture u gotovom proizvodu bilo najviše bakterija Lactobacillus casei, što potvrđuje da se ta vrsta najbolje prilagođava uvjetima proizvodnje. Novina i znanstveni doprinos. Proizveden je novi visoko kvalitetni sušeni fermentirani mesni proizvod zamjenom svinjske masti emulzijom maslinovog ulja i proteina iz puretine. Autohtone bakterije mliječno-kiselog vrenja s potvrđenim probiotičkim svojstvima in vitro mogle bi se primijeniti u proizvodnji trajnih kobasica na veliko. Dobiveni bi se izolati mogli primijeniti kao starter kulture za standardizaciju postupka i očuvanje tipičnih organoleptičkih i senzorskih svojstava kobasica. Osim toga, izolati poput L. casei 62, koji su pronađeni u velikom broju u gotovom proizvodu, svojom kompetitivnošću ne samo s patogenim sojevima, već i s autohtonom mikrobiotom, povećavaju sigurnost fermentiranih kobasica te imaju potencijalnu funkcionalnu vrijednost za potrošače

Rheological and textural properties of processed cheese

EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Biodegradable Films from Kefiran-Based Cryogel Systems

Kefiran, which was isolated from kefir grains, was used for the fabrication of cryogel-films in the presence of plasticizers, such as glycerol and sorbitol. Varying concentration ratios of the exopolysaccharide/plasticizer system were employed in the process of the cryogel-film formulation and their effect on the physical (film thickness, moisture content, and solubility) and the mechanical (tensile strength and elongation at break) properties of the films was monitored. Kefiran-film vapor adsorption isotherms were calculated, and a thermal analysis of the samples was also performed. The structural characteristics of the cryogel-films were observed using confocal laser scanning microscopy. The cryo-treatment, alongside the plasticizer addition, affected the physical and mechanical properties of the kefiran films, as well as their morphology. Increasing kefiran concentration resulted in increasing the film thickness, the moisture content, and the tensile strength, while decreased their solubility and their elongation at break. Kefiran-film adsorption isotherms were affected by the cryo-treatment, the kefiran concentration, and the plasticizer use and concentration. The thermal analysis of the kefiran films showed thermal stability. The presence of the plasticizers and their increment concentration resulted in decreasing the glass transition and the melting temperatures. The cryo-treatment and the presence of plasticizers resulted in the films appearing smoother. Glycerol proved to affect more than the sorbitol–water vapor adsorption and the morphology of kefiran films

Biodegradable Films from Kefiran-Based Cryogel Systems

Kefiran, which was isolated from kefir grains, was used for the fabrication of cryogel-films in the presence of plasticizers, such as glycerol and sorbitol. Varying concentration ratios of the exopolysaccharide/plasticizer system were employed in the process of the cryogel-film formulation and their effect on the physical (film thickness, moisture content, and solubility) and the mechanical (tensile strength and elongation at break) properties of the films was monitored. Kefiran-film vapor adsorption isotherms were calculated, and a thermal analysis of the samples was also performed. The structural characteristics of the cryogel-films were observed using confocal laser scanning microscopy. The cryo-treatment, alongside the plasticizer addition, affected the physical and mechanical properties of the kefiran films, as well as their morphology. Increasing kefiran concentration resulted in increasing the film thickness, the moisture content, and the tensile strength, while decreased their solubility and their elongation at break. Kefiran-film adsorption isotherms were affected by the cryo-treatment, the kefiran concentration, and the plasticizer use and concentration. The thermal analysis of the kefiran films showed thermal stability. The presence of the plasticizers and their increment concentration resulted in decreasing the glass transition and the melting temperatures. The cryo-treatment and the presence of plasticizers resulted in the films appearing smoother. Glycerol proved to affect more than the sorbitol–water vapor adsorption and the morphology of kefiran films

Effects of Greek pomegranate extracts in the antioxidant properties and storage stability of kefir

Background: Oxidation reactions are known to shorten the shelf life and cause damage to foods rich in fat, such as dairy products. One way to limit oxidation and increase the shelf life of fermented dairy products is to use natural antioxidants. The aim of this study was to examine the effect of adding pomegranate extracts in the antioxidant properties, rheological characteristics and the storage stability of the fermented product of kefir. Methods: The Pomegranate Juice (PGJ) and Peel Extracts (PGPE) (5%, 10% w/v) were added to kefir and the antioxidant properties were evaluated by using the methods of radical scavenging activity (DPPH) and Ferric Reducing Antioxidant Power Activity (FRAP). Spectrophotometric and instrumental methods were used to determine the Total Phenols (TPs), pH values, viscosity and flow behavioral index values of enriched with pomegranate kefir samples. The same properties were tested when kefir samples stored at 4°C for 7, 14, 21 and 28 days. Results: The addition of PGJ and PGPE results in an increase in the antioxidant activity (DPPH, FRAP) and total phenol content (TPs) of kefir samples. Increasing the concentration of the added PGJ and PGPE, results in an increase in the TP content and the DPPH activity of kefir. As far as the storage time is concerned, the results showed an increase in the amount of TP at 7th day and a reduction in the DPPH activity in the 14th day of storage. In contrary to the DPPH method, the increase in storage time has resulted in a reduction in antioxidant activity by the FRAP method. The addition of PGJ and PGPE in kefir results in a decrease in pH values while the pH of kefir samples increased during storage at 4°C for 28 days. The addition of PGJ and PGPE to kefir samples results to a decrease in viscosity and an increase in the flow behavior index. Increasing storage time results in increased flow behavior index of kefir samples. Conclusion: The addition of PGJ and PGPE increased the antioxidant activity and total phenols of the kefir product and preserved its properties during the total storage time of 28 days at 4°C. © 2019 Bentham Science Publishers