The effects of carbon dioxide addition to cheese milk on the microbiological properties of Turkish White brined cheese

This study invest0igated the effect of CO₂ added to achieve three pH levels: pH 6.1, pH 6.2 and pH 6.3 for treatments X, Y, Z, respectively, on some microbiological properties of Turkish White (TW) brined cheese. For each pH, four batches of cheese were produced from: raw milk with no added carbon dioxide (UR), raw milk with carbon dioxide (TR), pasteurised milk with no carbon dioxide addition (UP) and pasteurised milk with carbon dioxide addition (TP). The microbiological analysis of TW brined cheeses was carried out for 90 days of maturation period. Total aerobic mesophilic bacteria, mesophilic lactic acid bacteria, yeasts and moulds and coliform group were determined in control and CO₂ treatment groups. Mesophilic bacteria count was determined as 5.14, 5.29, 5.67 log cfu/g for pH 6.1, 6.2 and 6.3, respectively, in CO₂‐treated raw milk cheeses. Yeasts and moulds reduction increased significantly by applying CO₂ (P < 0.01). For TW cheese samples, the most significant microbial inactivation was detected at sample groups of pH 6.1.     

PRESERVATION OF BLUE-JACK MACKEREL (TRACHURUS PICTURATUS BOWDICH) SILAGE BY CHEMICAL AND FERMENTATIVE ACIDIFICATION

We compared acidified and lactic acid fermented silage approaches for the preservation of blue‐jack mackerel. Silages acidified with formic and propionic acids had stable pH (3.8) and low (19 mg/g N) levels of volatile nitrogen compounds (total volatile basic nitrogen, TVBN), but relatively high (82 g/100 g) final non‐protein‐nitrogen (NPN) values. The silage was fermented with Lactobacillus plantarum LU853, a homofermentative lactic acid bacterium with a high growth (0.51/h) and acidification rate at 37C (optimum temperature), able to grow in the presence of 40 g/L NaCl and to ferment sucrose and lactose. The silages at 37C reached safe pH < 4.5 values within 48–72 h, either (F2a) or not (F0), in combination with 20 g/kg salt addition; F2a acidified more rapidly, which may be an advantage for its microbiological stability. Proteolysis resulting in 53–59 g NPN/100 g N was lower in fermented than in acidified silages; however, in fermented silages, the levels of TVBN were much higher (50–80 mg TVBN/g N) than generally considered acceptable.     

Effects of sunflower honey on the physicochemical,microbiological and sensory characteristics in set type yoghurt during refrigerated storage

The primary purpose of this research was to monitor the influence of sunflower honey addition (2%, 4% and 6% w/v) to yoghurt milk on survival of the microbial flora of yoghurt and the physicochemical and sensory characteristics during refrigerated storage for 4 weeks. The water activity decreased according to the addition of honey with higher concentrations in the storage period (4°C). At the end of fermentation, pH values of yoghurt samples ranged between 4.33 (without honey) and 4.52 (addition of honey with 6%). The highest water holding capacity, consistency and the lowest brightness values were determined in the groups produced with 6% honey addition. The water holding capacity and a* (redness) values of the honey incorporated yoghurt samples increased during storage. Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus values of the yoghurt with honey increased compared with the control group samples (P < 0.01). Addition of honey to yoghurt milk has affected the vitality of the characteristics starters in the incubation and storage time of the yoghurt samples (P < 0.01). Optimum sweetness was obtained with the samples containing 4% honey level.     

Storage Temperature Effect on Histamine Formation in Big Eye Tuna and Skipjack

Notable histamine formation (>30 mg/100g) was detected in big eye tuna (Thunnus obesus) and skipjack (Katsuwonus pelamis) captured in Azorean waters and stored for 1,3 and 6 days at 22,10 and 4°C, respectively. Higher levels (p<0.05) of histamine were produced by skipjack reflecting its higher histidine content. Measurements of pH or volatile basic nitrogen were not adequate for estimating the extent of histamine-related health hazard. Counts of histamine-forming bacteria increased during storage at 4 and 10°C, and histamine formation was suppressed at 4°C. Storage temperature and histidine content were the main factors controlling histamine levels in tuna.