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U radu je prikazan razvoj novog tipa piva za tržiste, koje se dobiva vrenjem pri niskoj temperaturi u hladnjaku s pomoću imobiliziranog kvasca. Zamrznuta sladovina te stanice soja kvasca Saccharomyces cerevisiae AXAZ-1, koji je otporan na smrzavanje, imobilizirane su na cijevnom modulu i zasebno upotrijebljene za vrenje pri niskim temperaturama (2, 5 i 7 °C). Ispitan je pozitivan učinak cijevnog modula na vrenje pri niskim temperaturama, te je utvrđeno da smrznute imobilizirane stanice kvasca na cijevnom modulu bitno smanjuju brzinu vrenja u usporedbi sa smrznutim slobodnim stanicama, koje su preporučene za proizvodnju piva kod kuće. Imobilizacija je također povećala otpornost kvasca na niske temperature vrenja, pa se najniža moguća temperatura vrenja spustila s 5 na 2 °C. Pri proizvodnji visokokvalitetnog piva ispitani su sljedeći parametri: utjecaj temperature i početne koncentracije šećera na kinetiku vrenja. Analizom gotovog proizvoda potvrđeno je poboljšanje senzorskih svojstava proizvedenog piva, s niskom koncentracijom diacetila, povećanim udjelom polifenola, te poboljšanim profilom arome i bistroćom. Predloženi postupak proizvodnje piva u hladnjaku može se lako komercijalizirati za kućnu uporabu otapanjem sadržaja dvaju pakiranja, jednog sa suhom sladovinom i drugog sa suhim stanicama kvasca imobiliziranim na cijevnom modulu i otopljenim u vodi., Development of a novel directly marketable beer brewed at low temperature in a domestic refrigerator combined with yeast immobilization technology is presented in this study. Separately, freeze-dried wort and immobilized cells of the cryotolerant yeast strain Saccharomyces cerevisiae AXAZ-1 on tubular cellulose were used in low-temperature fermentation (2, 5 and 7 °C). The positive effect of tubular cellulose during low-temperature brewing was examined, revealing that freeze-dried immobilized yeast cells on tubular cellulose significantly reduced the fermentation rates in contrast to freeze-dried free cells, although they are recommended for home-made beer production. Immobilization also enhanced the yeast resistance at low-temperature fermentation, reducing the minimum brewing temperature value from 5 to 2 °C. In the case of high-quality beer production, the effect of temperature and initial sugar concentration on the fermentation kinetics were assessed. Sensory enrichment of the produced beer was confirmed by the analysis of the final products, revealing a low diacetyl concentration, together with improved polyphenol content, aroma profile and clarity. The proposed process for beer production in a domestic refrigerator can easily be commercialized and applied by dissolving the content of two separate packages in tap water; one package containing dried wort and the other dried immobilized cells on tubular cellulose suspended in tap water.

In the present study, probiotic sour milk was produced by freeze-dried Lactobacillus casei ATCC 393 cells, free or immobilized on wheat bran. Wheat bran was used with and without lignin removal. The aim was to evaluate the possibility to produce sour milk using immobilized probiotic biocatalysts that could be removed after the end of fermentation and be used in a next fermentation batch. The effect of the biocatalysts on product quality was also evaluated during 30 days of storage at 4 °C. The aroma profile, organic acids production, residual sugar content and culture viability were monitored during that period. The immobilized bacteria on wheat bran were better protected in the acidic environment of the sour milk fermentations, compared to free cells. The microbial populations (>7.5 log cfu g−1) were significantly higher in sour milks produced with the immobilized biocatalysts during the 30 day storage, while no growth of pathogenic microorganisms was observed. The microbiological, physicochemical, and sensory characteristics of the sour milks produced using the immobilized biocatalysts, indicated high commercialization potential of these products.

The aim of this investigation was to study the use of nano/micro-porous cellulosic materials (tubular cellulose, TC) produced by delignification of mango (Magnifera indica L.), sal (Shorea robusta G.) sawdust and rice husk (Oryza sativa L.) in various food bioprocesses. Specifically, the porous structure of TC renders it suitable for use as filter material in continuous cold pasteurization processes as well as biocatalyst (carrier for yeast immobilization) for alcoholic fermentation. Water contaminated with Saccharomyces cerevisiae or Lactobacillus bulgaricus cells was continuously pumped through TC filters. The effect of TC origin, type of contamination and microbial load on the operational stability of the system was assessed. The microbial load removal ranged between 99.9-88.2% and 92–77% for yeast and bacteria, respectively. The system operated efficiently for up to 55 days. Filter regeneration was done with hot water. Scanning electron micrographs showed the entrapment of cells in the TC filters. The TCs were further used as S. cerevisiae immobilization carriers for alcoholic fermentation of grape must and glucose media at 15 °C. Satisfactory fermentation rates, high ethanol content, ethanol productivity, and volatile by-products formation were observed. The TCs showed great potential for water pretreatment and food bioprocessing with simultaneous valorization of lignocellulosic biomass.

A novel continuous preservation process of apple juice using a nano/micro-porous cellulosic material (or “tubular cellulose”, abrrev. TC), is presented in this study. This investigation aims to the development of a non-thermal system for microbial stabilization, avoiding the degradation of food quality caused by heat. TC was used as filter in a packed-bed type bioreactor supplied with commercial apple juice contaminated with Saccharomyces cerevisiae or Lactobacillus plantarum cells at 4 °C. The effect of the filter size on the microbial load removal and chemical/sensory properties of the juice was evaluated. The system presented good operational stability during 55 and 30 days for the removal of yeast and bacteria, respectively. The increase of filter size improved the microbial removal yield and the system effectiveness. The organoleptic parameter values decreased after ΤC regeneration but then reached almost initial levels. The proposed process is a low-cost and promising alternative to existing thermal pasteurization technologies. Industrial relevance Conventional thermal pasteurization treatments are applied industrially for microbial stabilization of foods but significantly affect the organoleptic characteristics of the products. This study evaluated a novel non-thermal preservation method of contaminated apple juice that meets the consumer's demand for less processed products with high nutritional value. Commercial apple juice was contaminated with S. cerevisiae or L. plantarum cells and then was continuously pumped through tubular cellulose. The increased size of the filter leads to improved microbial removal yields. Despite the decrease of volatile compounds and colour at the start up of the process and after each filter regeneration with hot water, almost initial parameter values were achieved as the process evolved. The proposed technology can be a promising alternative of industrial pasteurization techniques for food applications.

In this study, tubular cellulose (TC), a porous cellulosic material produced by delignification of sawdust, was treated with a Trichoderma reesei cellulase in order to increase the proportion of nano-tubes. The effect of enzyme concentration and treatment duration on surface characteristics was studied and the samples were analyzed with BET, SEM and XRD. Also, a composite material of gelatinized starch and TC underwent enzymatic treatment in combination with amylase (320U) and cellulase (320U) enzymes. For TC, the optimum enzyme concentration (640U) led to significant increase of TC specific surface area and pore volume along with the reduction of pore diameter. It was also shown that the enzymatic treatment did not result to a significant change of cellulose crystallinity index. The produced nano-tubular cellulose shows potential for application to drug and chemical preservative delivery systems.

Sea buckhorn berries (SBB, Hippophae rhamnoides L.) were used as a novel support for immobilisation of the probiotic strain L. casei ATCC 393. The biocatalyst was employed for the development of a bioprocess for feta-type cheese production that leads to the improvement of quality and nutritional characteristics. Specifically, the effect of SBB supported biocatalyst on the microbiological safety and aroma profile of cheeses was compared with control samples and cheeses containing free L. casei cells showing superior properties with increased content of esters, alcohols and terpenes. The presence of probiotic culture, either in free or immobilised form, affected positively the physicochemical characteristics of cheeses during ripening. Cheeses with SBB had enriched aroma with terpenes and carbonyl compounds and higher probiotic cell population. The proposed bioprocess of employing SBB as immobilisation carrier shows great potential for commercialisation and application in manufacturing of probiotic functional dairy food. Fil: Terpou, Antonia. University of Patras; Grecia Fil: Gialleli, Angelika Ioanna. University of Patras; Grecia Fil: Bosnea, Loulouda. University of Patras; Grecia Fil: Kanellaki, Maria. University of Patras; Grecia Fil: Koutinas, Athanasios A.. University of Patras; Grecia Fil: Castro, Guillermo Raul. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Fermentaciones Industriales. Universidad Nacional de la Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Fermentaciones Industriales; Argentina

This investigation describes the development of a continuous “cold pasteurisation” process for wine, using a nano/micro-porous cellulosic material (tubular cellulose, TC), produced after delignification of wood sawdust, as filter in a packed column. The packed-bed bioreactor was supplied with white or red wine contaminated with Saccharomyces cerevisiae AXAZ-1 or Acetobacter pasteurianus, respectively, at low temperature. The effect of the TC filter size on microbial load removal was assessed. Scanning electron micrographs showed attachment of cells in the internal surface of the TC tubes, proving the removal of cells from wine. The effect of the continuous cold pasteurisation process on wine quality was examined by analysis of volatile compounds, organic acids, polyphenols content and colour intensity. Fourier transform infrared spectroscopy (FT-IR) spectra indicated presence of wine compounds on the TC filter. The microbial load removal remained constant to 97–100 % for a long period, with few required filter regenerations, which were done by washing with hot water (70–80 °C). The simplicity of the proposed process, and the low cost and abundance of the TC material can provide an alternative to existing expensive technologies for microbial stabilisation of wine prior to bottling.

Porous delignified cellulose (or tubular cellulose, abbr . TC) from Indian Mango ( Mangifera indica ) and Sal ( Shorea robusta ) wood and Rice husk, and TC/Ca-alginate/polylactic acid composites, were used as Lactobacillus bulgaricus immobilisation carriers leading to improvements in lactic acid fermentation of cheese whey and synthetic lactose media, compared to free cells. Specifically, shorter fermentation rates, higher lactic acid yields (g/g sugar utilised) and productivities (g/L d), and higher amounts of volatile by-products were achieved, while no significant differences were observed on the performance of the different immobilised biocatalysts. The proposed biocatalysts are of food grade purity, cheap and easy to prepare, and they are attractive for bioprocess development based on immobilised cells. Such composite biocatalysts may be used for the co-immobilisation of different microorganisms or enzymes (in separate layers of the biocatalyst), to efficiently conduct different types of fermentations in the same bioreactor, avoiding inhibition problems of chemical or biological (competition) nature.