Vinegar Production from Corinthian Currants Finishing Side-Stream: Development and Comparison of Methods Based on Immobilized Acetic Acid Bacteria.

Fruit wastes and side-streams can be used for vinegar production to create added value for the agri-food sector and enhance farmer incomes and local economies. In this study, methods for vinegar production by wild and selected acetic acid bacteria (the quick starter Acetobacter aceti and the acid-resistant Komagataeibacter europaeus), free (FC) and immobilized (IC) on a natural cellulosic carrier, are proposed using sweet wine made from the industrial finishing side-stream (FSS) of Corinthian currants as raw material. The results showed all cultures can produce vinegar with 46.65 ± 5.43 g/L acidity, from sweet FSS wine containing 5.08 ± 1.19% alcohol. The effect of immobilization was more obvious in the case of the selected culture, presenting better acetification efficiency, both fresh and after cold storage for 2 months. The vinegars had an antioxidant capacity of 263.5 ± 8.4 and 277.1 ± 6.7 mg/L (as ascorbic acid) and phenolic content 333.1 ± 12.0 and 222.2 ± 2.9 mg/L (as gallic acid) (for FC and IC, respectively). They also had a rich volatilome (140 compounds identified by SPME GC-MS), with higher percentages of esters identified in vinegars made by IC. The results are encouraging for vinegar production with IC of a mixed A. aceti and K. europaeus culture.

Thermal drying of Lactobacillus delbrueckii subsp. bulgaricus and its efficient use as starter for whey fermentation and unsalted cheese making.

Lactobacillus bulgaricus grown on whey was dried by a simple thermal drying method at the range 35-55 degrees C and its efficiency for lactic acid fermentation of whey was evaluated. Drying of cells in whey suspension in the examined temperature range did not affect significantly their viability (82-87% survival), indicating a protective effect of whey as both growth and drying medium. The kinetics of fermentation of whey and mixtures of whey/molasses using the dried culture were comparable to those of non-dried cells, and only low pH had a detrimental effect on the fermentation ability of the dried cells. Furthermore, dried L. bulgaricus, free or immobilized on casein coagulates, was used as starter for the production of unsalted hard-type cheese. The effects of the amount of starter culture and the immobilization technique, the evolution of microbial counts, and the sensory properties of the produced cheeses were evaluated during ripening at various temperatures.

Scale-up of thermally dried kefir production as starter culture for hard-type cheese making: an economic evaluation.

This paper concerns the effect of thermal-drying methodology on the investment cost for dried kefir cells production in order to be used as starter culture in cheese manufacturing. Kefir cells were produced at pilot plant scale using a 250-L bioreactor and whey as the main substrate. Kefir cells were subsequently dried in a thermal dryer at 38 degrees C and used as a starter culture in industrial-scale production of hard-type cheeses. The use of thermally dried kefir as starter culture accelerated ripening of cheeses by increasing both lipolysis and fermentation rate as indicated by the ethanol, lactic acid, and glycerol formation. Additionally, it reduced coliforms and enterobacteria as ripening proceeded. This constituted the basis of developing an economic study in which industrial-scale production of thermally dried kefir starter culture is discussed. The industrial design involved a three-step process using three bioreactors of 100, 3,000, and 30,000 L for a plant capacity of 300 kg of thermally dried kefir culture per day. The cost of investment was estimated at 238,000 euro, which is the 46% of the corresponding cost using freeze-drying methodology. Production cost was estimated at 4.9 euro/kg of kefir biomass for a 300-kg/day plant capacity, which is the same as with the corresponding cost of freeze-dried cells. However, the estimated added value is up to 10.8 x 10(9) euro within the European Union.

Thermally-dried free and immobilized kefir cells as starter culture in hard-type cheese production.

In an attempt to seek for suitable dried cultures, thermally-dried kefir was employed as starter in hard-type cheese production and tested in cheeses ripened at 5, 18 and 22 degrees C. Both free and immobilised on casein kefir cells were used and compared to cheese made without starter culture. Cheese products made with free cells of kefir culture were characterized by longer preservation time, improved aroma, taste, texture characteristics and increased degree of openness. Volatile profiles obtained by GC/MS analysis revealed a 216% increase in total concentration of esters, organic acids, alcohols and carbonyl compounds between cheeses prepared with and without kefir culture.

Whey valorisation: a complete and novel technology development for dairy industry starter culture production.

Whey is the major by-product of the dairy industry, produced in large quantities and usually disposed off causing major environmental pollution, due to its high organic load that makes treatment cost prohibitive. This paper comprises a contribution on the valorisation of this high polluting liquid waste of the dairy industry, based on research for the production of novel dairy starter cultures using whey as raw material. Starter cultures are used for cheese ripening in order to: (i) accelerate ripening, (ii) improve quality and (iii) increase shelf-life. The developed technology involves biomass production from whey followed by thermal drying of cultures. Specifically, Kluyveromyces marxianus, Lactobacillus bulgaricus and kefir yeasts were thermally dried, and their efficiency in lactose and milk whey fermentations was studied. The most suitable culture regarding its technological properties was kefir, which was used for cheese ripening in freeze-dried and thermally dried form. Besides the reduction of production cost, which is an essential requirement for the food industry, the use of thermally dried kefir displayed several other advantages such as acceleration of ripening, increase of shelf-life, and improvement of hard-type cheese quality.

Production of hard-type cheese using free or immobilized freeze-dried kefir cells as a starter culture.

This study provides a contribution to hard-type cheese starter culture production through the use of a freeze-dried culture in the ripening of hard-type cheeses. The effect of initial cell concentration, ripening temperature, and cell immobilization of kefir on the degree of openness, mold spoilage, microbial associations, physicochemical characteristics, and aroma-related compounds was studied. Use of kefir starter cultures resulted in cheese with an increased shelf life and resistance to spoilage as compared to control cheeses without kefir inoculants. Furthermore, the freeze-dried kefir culture improved aroma, taste, and texture characteristics while increasing the degree of openness in comparison to traditional hard-type cheese products. The kefir culture resulted in an increase in counts of total aerobic bacteria, yeasts and molds, lactococci, and lactobacilli until the 15th day of ripening. From then on, only lactobacilli counts increased, reaching levels up to 9.17 log CFU/g in cheeses ripened at 5 degrees C using freeze-dried kefir cells immobilized on casein. SPME-GC/MS analysis revealed major differences in volatile composition, especially with regard to alcohols (up to 75%), carbonyl compounds (up to 75%), and esters (up to 64%) between cheeses made with kefir cells and cheeses made without kefir inoculants.