Investigation of the effects of different processing methods on the selected nutritional properties of pumpkin and determining the appropriate process for pumpkin yogurt

The processing methods, especially cooking, can cause quality losses, particularly in the nutritional value of the fresh product. This study investigated the effects of preprocessing methods on the nutritional properties of pumpkin and the physicochemical and sensory properties of pumpkin yogurt. Two different pumpkin varieties (Cucurbita pepo and Cucurbita maxima) were subjected to three different preprocessing methods (freeze-drying, boiling, and baking). Boiling significantly increased antioxidant activity (p ≤ .05), followed by baking. C. maxima had higher TDF and TPC than C. pepo, but in both pumpkin varieties, TDF did not change with heat treatment (boiling and baking), while TPC decreased. Mineral contents remained the same or decreased with heat treatment, except for Mn and Fe. In particular, the addition of C. maxima significantly affected the color parameters (L*, a*, b*) of yogurt and improved WHC (from 68.9% to 91.6%) and hardness (from 58.0 to 193.5 g; p ≤ .05). The sensory evaluation concluded that heat-treated (boiled and baked) samples were preferred more than freeze-dried raw ones. In conclusion, the results revealed that adding boiled and baked pumpkins, especially the preference for C. maxima instead of C. pepo, improved the quality parameters of yogurt.

Coagulation temperature and smoking time determine product quality and shelf life of the acid-heat coagulated Circassian cheese

This study examined the effects of process parameters on acid-heat coagulated Circassian cheese. For this purpose, cheeses were produced at coagulation temperatures of 70°C and 90°C, and smoked for 0, 2.5, and 6 h in both summer and winter. Microbiological, textural, proteolytic, and sensorial changes were observed for 90 days at 30-day intervals. According to the results, coagulation at 90°C instead of 70°C formed a firmer structure. Six-hour smoking time instead of 2.5-h provided higher dry matter, reduced proteolysis rates, and extended the microbial shelf life. In addition, higher (6 h) smoking decelerated sourness while resulting in intense smoke flavor and higher lipolytic activity. In conclusion, seasonal changes in milk and applied the process conditions revealed significant differences in the quality parameters and shelf life of acid-heat coagulated Circassian cheese.

Inhibitory Effect of Sodium Alginate Nanoemulsion Coating Containing Myrtle Essential Oil (Myrtus communis L.) on Listeria monocytogenes in Kasar Cheese

The present study aimed to characterize the physical properties of nanoemulsion-based sodium alginate edible coatings containing myrtle (Myrtus communis L.) essential oil and to determine its inhibitory effects on Listeria monocytogenes in fresh Kasar cheese during the 24-day storage at 4 °C. The GC-MS analysis showed that the main components of myrtle essential oil were 1,8-cineol (38.64%), α-pinene (30.19%), d-limonene (7.51%), and α-ocimene (6.57%). Myrtle essential oil showed an inhibitory effect on all tested L. monocytogenes strains and this effect significantly increased after ultrasonication. Minimum inhibitory and minimum bactericidal concentrations of myrtle essential oil nanoemulsion were found to be 4.00-4.67 mg/mL and 5.00-7.33 mg/mL, respectively. The antibacterial activity of myrtle essential oil nanoemulsion against L. monocytogenes was confirmed by the membrane integrity and FESEM analyses. Nanoemulsion coatings containing myrtle essential oil showed antibacterial activity against L. monocytogenes with no adverse effects on the physicochemical properties of cheese samples. Nanoemulsion coatings containing 1.0% and 2.0% myrtle essential oil reduced the L. monocytogenes population in cheese during the storage by 0.42 and 0.88 log cfu/g, respectively. These results revealed that nanoemulsion-based alginate edible coatings containing myrtle essential oil have the potential to be used as a natural food preservative.

Impact of different starter cultures and Lactobacillus helveticus on volatile components, chemical and sensory properties of pasta filata cheese

L.helveticus is known to follow mainly similar metabolic pathways to contribute to cheese flavor with S. thermophilus and L. delbrueckii subsp. bulgaricus. In this study, the flavor contributions of commercial S. thermophilus starter cultures of different brands and L. helveticus adjunct culture to pasta filata type fresh Kashar cheese were investigated. L. helveticus affected the buttery aroma components of fresh Kashar cheese and resulted in low diacetyl content. In addition, acetaldehyde and other aroma components of L. helveticus added cheese was found to be higher than control and modified control cheeses. On the other hand, the modified control sample containing S. thermophilus from Danisco instead of Chr-Hansen in the control was closer to the control sample in terms of volatile profile. As the shelf-life progressed, the contribution of alcohols and hydrocarbons to volatile components decreased, while the contribution of ketones, which was the dominant group, increased in all products. When the proteolysis and lipolysis levels were examined, the control sample differed from the other two cheese samples with its high proteolysis and lipolysis rate. In summary, the rates of increase in water-soluble nitrogen and free fatty acid contents in 8 weeks of storage (from 18 to 72 days) were determined as 61% and 47%, respectively, in the control Kashar cheese, while it was 39% and 27% in the L. helveticus added sample, and 37% and 28% in the modified control sample. Finally, the sensory scores revealed that cheese flavor and texture preferences could be increased with the addition of L. helveticus.

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L. helveticus differed aroma profile of pasta filata type cheese - Kashar cheese.

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L. helveticus reduced diacetyl and increased acetaldehyde concentration.

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Different brands of S. thermophilus differentiated proteolysis and lipolysis levels.

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Different brands of S. thermophilus showed similar aroma profiles.