Today, cheese is valued because of its high nutritional value and unique characteristics. Improving the texture and flavor of cheese by selecting suitable starter cultures is an important way to promote the development of cheese industry. The effect of starter cultures on the physicochemical and textural properties and volatile compounds during the ripening of semihard goat cheese were investigated in this work. Different starter cultures-mesophilic (M) and thermophilic starters (T), Lactobacillus plantarum ssp. plantarum ATCC 14917 (Lp), a mix of the M and T starters (M1), and mix of the M, T, and Lp starters (M2)-were used in the production of the goat cheeses. Volatile compounds were determined by a solid-phase microextraction/gas chromatography-mass spectrometric (SPME/GC-MS) method. The results showed that the moisture content of cheeses produced with the 5 kinds of starter cultures decreased after maturation, whereas ash content increased. The pH values of goat cheeses decreased first and then increased during maturity, and the pH value of M2 cheese was the lowest among the cheeses. The hardness and chewiness of the cheeses increased with increasing maturity, whereas cohesiveness, springiness, and resilience showed the opposite tendency. The 60-dold cheese made with Lp had the highest chewiness, cohesiveness, springiness, and resilience, whereas the 60-d-old cheese made with M2 had the highest hardness. A total of 53 volatile components were identified by SPME/GC-MS, and carboxylic acids, alcohols, ketones, and esters were the 4 major contributors to the characteristic flavors of the cheeses. Volatile components and their contents differed greatly among the produced cheeses. The M2 cheese contained the highest relative content of the main volatile compounds (90.10%), especially butanoic acid and acetoin. Through a comprehensive comparison of the results, we concluded that M2 cheese had a dense texture and milky flavor, and M2 is a potential starter culture candidate for the production of goat cheese.

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Rapid, accurate, sensitive, and real-time detection of streptomycin (STR) residues in dairy products is very important. In this work, for the rst time, the gold nano ower/polyethyleneimine functionalized metal organic framework (AuNF-PEI-MIL-101(Cr)) nanocomposites were synthesized via hydrothermal method and characterized using various techniques (SEM, TEM, XRD, FT-IR and XPS). Then, a novel electrochemical aptasensor was constructed for the detection of STR based on AuNF-PEI-MIL-101(Cr) nanocomposites. The gold electrode (GE) modi ed with AuNF-PEI-MIL-101(Cr) can immobilize a large number of thiolated STR aptamer via the Au-S bond. When the target STR was in the presence, the current signal was reduced due to the speci c binding of STR towards the aptamer. The results indicated that the aptasensor had a wide linear range towards STR (0.01-400 nM) with a low detection limit of 0.003 nM under the optimal conditions. Moreover, the aptasensor exhibited good selectivity, reproducibility, and stability. In addition, the STR in the cow, sheep, and goat milk samples was detected by the spiked recovery method, and satisfactory results were obtained. The method provides an e cient pathway for the sensitive detection of STR. Highlights 1. The presence of AuNF-PEI-MIL-101(Cr) on the sensor surface increases the aptamer loading e ciency.2. The developed aptasensor exhibits wide linear range and low detection limit for streptomycin.3. The aptasensor shows high sensitivity and selectivity. 4. Fabricated aptasensor can be proposed for monitoring other antibiotics in foodstuffs.

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