The properties of whey protein based film containing AgNPs biosynthesised by Aspergillus niger.

No abstract

In Turkey, legislation reduced the salt content in fresh cheeses from 10% to 6.5% in dry matter (DM). This study investigated the effect of salt reduction on the fate of acid‐ and salt‐adapted Escherichia coli O157:H7 and Listeria monocytogenes, as well as the textural quality of recombined nonfat cheese. The cheese was manufactured using milk protein concentrate (85% protein) and skim milk powder (35% protein). After pasteurization and addition of starter culture (0.1%), cheese milk was inoculated with acid‐ or salt‐adapted pathogens (1 × 103 cfu/g). Following salting (4%, 6%, 8%, or 10% in DM) and fermenting (24 hr/30 °C), the microbiological and textural properties of the cheese were analyzed during 8 weeks of storage at 4 °C. Salt concentration did not affect E. coli survival during storage (p > .05). Acid‐adapted L. monocytogenes and E. coli survived 1 week longer than the unadapted control. Cheese hardness was unaffected (p > .05) by the salt concentration. Practical applications The results of the present study can be used to assess the risk of survival of acid‐ and salt‐adapted Listeria monocytogenes or Escherichia coli O157:H7 in nonfat cheese (with different salt concentration) produced from unpasteurized milk.

The purpose of this study is to isolate, identify and compare lactic acid bacteria responsible for fermentation from pickles produced with vinegar and acid whey (AW). For this reason, fermented cornichon pickles were produced by using AW and vinegar as brine media. Colonies with different morphologies were selected and isolated at the 0, 7, 14, 21, 35, 49, 77 and 105th days of fermentation. A total of 139 isolates were obtained. Salt, acidity and pH values of brine and cornichon were followed on each analysis day. Growth and gas formation from glucose of isolates at different temperatures (10, 45, and 50 o C), salt concentrations (2, 4.5, and 10% (w/w)), different pH values (3, 4.5, and 9.6), were analyzed. Eight isolates were determined as heterofermentative according to their ability to produce CO2 from glucose. The isolates were observed to show the highest growth at 10 o C, and a very few isolates developed at 45 o C and 50 o C. No isolates were able to grow at pH 9.6, 25 of the isolates were able to grow at pH 4, and only 4 isolates were able to grow at pH 3. Only one isolate was able to show resistance to 10% salt concentration. Almost all isolates grew at 2% and 6.5% salt concentrations. 48 selected isolates were identified with API 50 CHL. 19 isolates were determined as Lactobacillus pentosus (8 vinegar, 11 AW) and 29 isolates as Lactobacillus plantarum (16 vinegar, 13 AW). As a result, L. plantarum and L. pentosus species were the dominant bacteria for cornichon pickles produced with AW and vinegar. Microbial flora in the pickles produced with two different brines were similar. The results show that AW can be successfully used for pickle production.

Bu çalışmada, atık çay ekstraktından üretilen Aspergillus niger’den kimyasal yöntemlerle kitosan özütlenerek, bu kitosan örneklerinin belirli özellikleri araştırılmıştır. Kurutulmuş atık çaylardan %5, 10 ve 20 konsantrasyonlarda hazırlanan karışımlar sterilize edilip süzüldükten sonra A. niger aşılanmış ve 25°C'de 5 gün inkübe edilmiştir. Elde edilen biyokütleden kimyasal yöntem kullanılarak kitosan ekstrakte edilmiştir. Elde edilen kitosanın yapısal özellikleri FT-IR, FESEM ve NMR ile belirlenmiştir. Üretilen kitosanın antimikrobiyal özellikleri Gram pozitif ve Gram negatif bakterilere, mayalara ve küflere karşı disk difüzyon testi kullanılarak analiz edilmiştir. Sonuçlar, %5, 10 ve 20 konsantrasyonlarda hazırlanan çay ekstraktlarında üretilen A. niger misellerinin kitosan ekstraksiyon veriminin sırasıyla %13.98, 15.71 ve 17.57 olduğunu göstermiştir. Elde edilen FT-IR, FESEM ve NMR spektrumlarının benzer çalışmalarda rapor edilen A. niger‘den üretilen kitosan ve ticari kitosan ile uyumlu olduğu görülmüştür. Gram pozitif ve negatif bakterilere karşı %1 ve 2-4 kitosan solüsyonları sırasıyla 7 ile 8 mm inhibisyon zonu oluşturmuştur. Saccharomyces cerevisiae kitosana karşı en hassas kültür olarak belirlenmiştir. Ticari kitosan, fungal kitosana göre test edilen mikroorganizmalara karşı daha fazla antimikrobiyal aktivite göstermiştir. Fungal kitosanın deasetilasyon derecesi %92 olarak bulunmuştur. Araştırmada elde edilen bulgulara göre, çevre açısından önem kazanan atık maddelerin değerlendirilmesi amacıyla atık çaylarda geliştirilen A. niger küfünden kitosan üretimi ilk defa gerçekleştirilmiş olup, çalışma bu konudaki araştırmalar için yol gösterici niteliktedir.