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During the past years, there has been a growing interest in the bioproduction of propionic acid by Propionibacterium. One of the major limitations of the existing models lies in their low productivity yield. Hence, many strategies have been proposed in order to circumvent this obstacle. This article provides a comprehensive synthesis and review of important biotechnological aspects of propionic acid production as a common ingredient in food and biotechnology industries. We first discuss some of the most important production processes, mainly focusing on biological production. Then, we provide a summary of important propionic acid producers, including Propionibacterium freudenreichii and Propionibacterium acidipropionici, as well as a wide range of reported growth/production media. Furthermore, we describe bioprocess variables that can have impact on the production yield. Finally, we propose methods for the extraction and analysis of propionic acid and put forward strategies for overcoming the limitations of competitive microbial production from the economical point of view. Several factors influence the propionic acid concentration and productivity such as culture conditions, type and bioreactor scale; however, the pH value and temperature are the most important ones. Given that there are many reports about propionic acid production from glucose, whey permeate, glycerol, lactic acid, hemicelluloses, hydrolyzed corn meal, lactose, sugarcane molasses and enzymatically hydrolyzed whole wheat flour, only few review articles evaluate biotechnological aspects, i.e. bioprocess variables., U posljednje je vrijeme porastao interes za biološku proizvodnju propionske kiseline s pomoću bakterije Propionibacterium. Glavni nedostatak postojećih modela je slab prinos, zbog čega su predložene različite strategije rješavanja tog problema. U ovom su radu opsežno prikazana bitna biotehnološka obilježja postupaka dobivanja propionske kiseline, jednog od uobičajenih sastojaka u prehrambenoj i biotehnološkoj proizvodnji. U prvom dijelu opisujemo najznačajnije proizvodne procese, s naglaskom na biološku proizvodnju, a zatim navodimo bakterije koje proizvode propionsku kiselinu, kao što su Propionibacterium freudenreichii i Propionibacterium acidipropionici, te različite podloge za rast ili proizvodnju. Osim toga, opisujemo varijable procesa koje mogu utjecati na prinos. Naposljetku, predlažemo metode ekstrakcije i analize dobivene propionske kiseline, te ističemo strategije pomoću kojih se mogu zaobići ekonomska ograničenja procesa uzrokovana kompeticijom mikroorganizama tijekom proizvodnje. Na koncentraciju propionske kiseline i produktivnost procesa utječe više čimbenika, kao što su: sastav podloge, tip i veličina bioreaktora te pH-vrijednost i temperatura kao najvažniji čimbenici. Objavljen je velik broj radova o proizvodnji propionske kiseline iz glukoze, permeata sirutke, glicerola, mliječne kiseline, hemiceluloze, hidrolizirane sačme kukuruznih klica, laktoze, melase šećerne trske, te brašna od cjelovitog zrna pšenice hidroliziranog pomoću enzima, ali vrlo mali broj revijalnih prikaza procjenjuje biotehnološke aspekte proizodnje, odnosno varijable bioprocesa.

Svrha je ovog istraživanja bila procijeniti svojstva dvaju tipova prebiotičkih kobasica, pripremljenih s rezistentnim škrobom i ekstraktom β-glukana (u omjerima 2,216:1,328 i 2,75:1,875), tijekom prženja i skladištenja pri niskim temperaturama. Određeni su indeksi oksidacijske stabilnosti i broj mikroorganizama. Dodatak dvaju prebiotičkih dijetalnih vlakana povećao je gubitke pri prženju i adsorpciju ulja. Međutim, količina vlage u prebiotičkim kobasicama nakon proizvodnje bila je veća u usporedbi sa standardnim (neprebiotičkim) kobasicama, te se postepeno smanjivala tijekom skladištenja. Rezultati pokazuju da dodatak preporučenog omjera rezistentnog škroba i β-glukana (2,216:1,328) može dovesti do smanjenja oksidacije masti u kobasicama tijekom skladištenja zbog antioksidacijskih svojstava ekstrakta β-glukana, no dodatak većih količina rezistentnog škroba i β-glukana nije moguć zbog daljnjeg porasta oksidacije masti. Konačan broj živih stanica rastao je do četrdeset i petog dana, nakon čega je došlo do njegovog postepenog pada. Dodatak ekstrakta β-glukana poboljšao je antioksidacijska svojstva proizvoda. Također, njegov antimikrobni učinak i smanjenje udjela vlage mogli bi inhibirati rast mikroorganizama. Nadalje, dodatak rezistentnog škroba doveo je do povećanja tiobarbiturnog i peroksidnog broja., This study aims to evaluate the performance of two types of prebiotic sausages formulated with resistant starch (RS) and β-glucan (BG) extract (in ratios of 2.22:1.33 and 2.75:1.88) during frying and chilled storage. The oxidative stability indices and microbial counts were determined. The incorporation of two types of prebiotic dietary fibre increased frying loss and oil absorption. However, the moisture content of prebiotic sausages after production was higher than of conventional sausages and it decreased significantly during storage. The use of sausage sample containing 2.22 % RS and 1.33 % BG as a recommended formulation can decrease fat oxidation of sausages during storage due to antioxidant properties of BG extract, but higher levels of RS and BG could not be used due to further increase in fat oxidation. Total viable count increased up to day 45 and decreased afterwards. The addition of BG extract improved the antioxidant properties of sausages. Additionally, the antimicrobial properties of BG and moisture reduction could inhibit microbial growth. Moreover, the addition of RS caused an increase in thiobarbituric acid and peroxide values.

In the current study, the antibacterial effect of Echinophora platyloba essential oil and common liquid smoke (individually and in combination) against Staphylococcus aureus in beef meat samples is investigated. Using an automated microbiological growth analyser and the turbidimetric technique, the minimum inhibitory concentrations (MIC) and the minimum bactericidal concentrations (MBC) of the essential oil and liquid smoke were determined. Anti-S. aureus activity of essential oil and liquid smoke (individually and in combination) was defined by disk diffusion assay, generation time and cell constituent release. Apart from that, the interactions between these two compounds were measured by the checkerboard assay and by calculating the fractional inhibitory concentration (FIC) indices. Related MIC values of essential oil and smoke were found to be 7200 and 5500 mg/L, and MBC values were 8500 and 8000 mg/L, respectively. The conducted organoleptic assay showed that the addition of 0.05 g of essential oil and 0.6 g of liquid smoke to 100 g of meat samples did not have adverse effect on the overall acceptance. Weaker antibacterial effect against Staphylococcus aureus was observed when only Echinophora platyloba essential oil was used than when it was used in combination with liquid smoke., U radu je ispitan pojedinačni i zbirni učinak esencijalnog ulja biljke Echinophora platyloba i primarnog kondenzata dima na suzbijanje rasta bakterije Staphylococcus aureus u uzorcima goveđeg mesa. Pomoću automatskog sustava za detekciju mikrobiološkog rasta i turbidimetrije određene su minimalna inhibicijska koncentracija i minimalna baktericidna koncentracija esencijalnog ulja i primarnog kondenzata dima. Pojedinačni i zbirni antibakterijski učinak esencijalnog ulja i primarnog kondenzata dima ispitani su disk difuzijskom metodom, određivanjem generacijskog vremena i mjerenjem apsorbancije otpuštenog staničnog sadržaja bakterije Staphylococcus aureus. Osim toga, ispitana je interakcija između ta dva antimikrobna agensa mikrorazrjeđenjem u bujonu (tzv. checkerboard testom) i određivanjem indeksa interakcije. Minimalna inhibicijska koncentracija esencijalnog ulja bila je 7200 mg/L, a primarnog kondenzata dima 5500 mg/L, dok je minimalna baktericidna koncentracija esencijalnog ulja bila 8500 mg/L, a primarnog kondenzata dima 8000 mg/L. Ispitana su organoleptička svojstva uzoraka mesa i utvrđeno je da dodatak 0,05 g esencijalnog ulja i 0,6 g kondenzata dima u 100 g uzorka nije utjecao na prihvatljivost proizvoda. Esencijalno ulje biljke Echinophora platyloba imalo je slabiji učinak na suzbijanje rasta bakterije Staphylococcus aureus od kombinacije esencijalnog ulja i primarnog kondenzata dima.

In this study, the D-optimal mixture design methodology was applied to determine the optimised proportions of inulin, β-glucan and breadcrumbs in formulation of low-fat beef burgers containing pre-emulsified canola and olive oil blend. Also, the effect of each of the ingredients individually as well as their interactions on cooking characteristics, texture, colour and sensory properties of low-fat beef burgers were investigated. The results of this study revealed that the increase of inulin content in the formulations of burgers led to lower cooking yield, moisture retention and increased lightness, overall acceptability, mouldability and desired textural parameters. In contrast, incorporation of β-glucan increased the cooking yield, moisture retention and decreased lightness, overall acceptability, mouldability and desired textural parameters of burger patt ies. The interaction between inulin and β-glucan improved the cooking characteristics of the burgers without significantly negative effect on the colour or sensory properties. The results of the study clearly stated that the optimum mixture for the burger formulation consisted of (in g per 100 g): inulin 3.1, β-glucan 2.2 and breadcrumbs 2.7. The texture parameters and cooking characteristics were improved by using the mixture of inulin, β-glucan and breadcrumbs, without any negative effects on the sensory properties of the burgers., U ovom je radu pomoću D-optimalnog dizajna određen optimalan omjer inulina, β-glukana i krušnih mrvica u smjesi za pljeskavice kojoj je prethodno dodana mješavina repičinog i maslinovog ulja. Osim toga, ispitan je pojedinačan i zbirni učinak sastojaka na kalo kuhanja, teksturu, boju i senzorska svojstva pljeskavica sa smanjenim udjelom masnoća. Rezultati pokazuju da se povećanjem udjela inulina povećao kalo kuhanja, smanjilo zadržavanje vlage, a dobivene su pljeskavice dobre teksture, svjetlije boje, koje se lako oblikuju te nakon pečenja postižu bolje senzorske ocjene. Interakcijom inulina i β-glukana poboljšana su svojstva pljeskavica tijekom pečenja, bez negativnog učinka na boju i senzorske osobine. Optimalna smjesa za izradu pljeskavica dobivena je dodatkom 3,1 g inulina, 2,2 g β-glukana i 2,7 g krušnih mrvica. Tekstura pljeskavica te njihova svojstva tijekom pečenja bitno su poboljšana dodatkom inulina, β-glukana i krušnih mrvica, pri čemu se senzorske ocjene nisu smanjile.