Bae et al. Appl Biol Chem (2020) 63:66 https://doi.org/10.1186/s13765-020-00539-5 ARTICLE Open Access Physicochemical changes during 4 weeks ripening of Camembert cheeses salted with four types of salts Hyung Churl Bae1, Joong Hyeon Nam1, Gereltuya Renchinkhand1, Suk‑Ho Choi2 and Myoung Soo Nam1* Abstract The objectives of this study were to compare physicochemical, rheological and sensory characteristics of Camembert cheeses salted with 4 types of salts (refned salt, baked refned salt, sun‑dried salt, and Himalayan rock salt) during 4 weeks ripening period. The pH of Camembert cheese was 7.2 in the sun‑dried salt, which was the highest than the other three types of salts. The viable lactic acid bacteria (LAB) counts after 4 weeks ripening of the cheeses with 4 types of salts were 1.4 108, 1.6 108, 1.3 108, and 1.3 108 CFU/ml, respectively. The water soluble nitrogen level of the cheese salted× with Himalayan× rock× salt was the× highest (109.23 µg/g) among those of all the cheeses at 4 weeks ripening. Organic acids in all the cheeses decreased as the ripening period advanced. Protein hydrolysis proceeded faster refned salted cheese than other salted cheeses after 4 weeks ripening. Octadecanoic acid and hexa‑ decanoic acid (volatile fatty acid) which were detected in the cheeses with refned salt and Himalayan rock salt were lower than those with baked refned salt and sun‑dried salt. In terms of textural characteristics there were substantially steep decreases in hardness, gumminess, and chewiness after 4 weeks ripening, while springiness and cohesiveness decreased less in all the Camembert cheeses. With respect to sensory properties, the taste score of the cheese with refned salt were signifcantly higher than those with baked refned salt, sun‑dried salt and Himalayan rock salt. These results suggested that the refned salt should be recommended for Camembert cheese making. Keywords: Camembert cheese, Salts, Physicochemical characteristic, Texture, Volatile fatty acid Introduction mold protease and lipase transformed rapidly insoluble Te soft and mold-ripened cheeses the most well known casein into water soluble peptides. in the world is Camembert cheese which is aged by inoc- In cheese ripening terminology, cheese ripening is ulating with Penicillium camembert and Geotrichum can- usually divided into interior or surface ripened cheese. didum. It is native of the Camembert region of northern Surface ripened cheese is divided into smear- and mold- France. Te cheese is ripened very quickly due to high ripened cheese. Typical examples of interior ripened moisture content and rapid growth of the surface mold cheeses are cheeses that are either submerged in brine [1]. Te action of mold protease, in addition to the prote- and stored in barrels, tins or airtight cartons cheeses that olytic actions of the coagulant and the protease from the are wrapped in plastic foil directly after production and starter culture, transforms the insoluble casein into acid- stored in this way, like rindless varieties of Continental soluble N fragments [2]. Especially, the strong activity of cheeses. All ripened cheeses are subject to a ripening process by which the cheese constituents are modifed or *Correspondence: [email protected] degraded through the action of indigenous milk enzymes, 1 Department of Animal Biosystem Science, College of Agriculture added enzymes and enzymes of microbial origin. Over and Life Sciences, Chungnam National University, Daejeon 34134, Republic of Korea and above the general interior ripening many cheeses are Full list of author information is available at the end of the article subject to surface ripening. Surface ripening may again © The Author(s) 2020. This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creat iveco mmons .org/licen ses/by/4.0/. Bae et al. Appl Biol Chem (2020) 63:66 Page 2 of 12 be divided into smear ripened cheeses and mold rip- Salts ened cheeses [3]. Ripening of the surface mold-ripened Four types of salts used were refned salt (Hanju Ltd., cheeses, Camembert and Brie, is characterized by the Korea), baked refned salt (Hanju Ltd., Korea), sun-dried very marked softening and almost liquefaction of the salt (Shinyi Ttd., Korea), and Himalayan rock salt (Irae cheese body from surface to center. Tis ripening pat- Marketing Ltd., Pakistan). Salting was carried out in 21% tern is due mainly to combination of αs1-casein hydrolysis brine for 70 min at 4 °C. and pH gradient decreasing from surface to center, due to ammonia production by the surface mold, P. cam- Ripening of cheese emberti, and its inward difusion, catabolism of lactic Camembert cheeses were prepared by the Scott [14] acid, and outward difusion of calcium [4–6]. Salt infu- method (Fig. 1). Initially, they were ripened for 1 week in ences cheese ripening principally through its efect on the ripening room (12 °C, RH 95%), and then secondary water activity. Among the principal efects of salts are ripening was carried out at 4 °C for 2-4 weeks. control of microbial growth and enzyme activity, syner- esis of the curd and subsequent reduction of moisture pH of cheese curd, and physical changes in cheese proteins. pHs of cheese samples were determined weekly using the Te salt level of cheese ranges from ~ 0.7% in Emmental methods [15]. A 10 g cheese sample and 20 ml sterilized to ~ 6% for Domiati. Te salt level of Camembert cheese water were homogenized using a homogenizer (ULTRA is 2.5% [7]. Te major feature of cheese salting is direct TURRAX T25, Janke & Kunkel, IKA-Labortechnic Ger- contribution to favor [8, 9]. Saltiness of cheese is highly many) for 5 min at 20,000 rpm, and then the pH of a sam- appreciated by many peoples and regarded as one of the ple was measured weekly for 4 weeks using a pH meter four basic favors. Te characteristic taste of salt, sodium (S-20 K, Mettler Toredo Co., USA) [16]. chloride, is due to sodium ion [10]. Few studies have been conducted on the efect of salt Viable cell count types to natural cheeses, especially in Camembert cheese. Cheese samples were taken weekly, mixed with sterilized Terefore, the objectives of this study were to prepare. water at 1:2 ratio as was done for pH. Te number of via- Camembert cheeses with refned salt, baked refned ble cell count was determined by the method [17], using salt, sun-dried salt, and Himalayan rock salt and to com- Standard plate count agar (Becton, Dickinson Co., USA) pare physicochemical, textural and sensory characteris- and BCP agar (Eiken Chemical Co., Ltd. Japan). tics of the Camembert cheeses during 4 weeks ripening periods. Materials and methods Compositions of raw milk and Camembert cheese Raw cow milk was obtained from the milking herd of Holstein–Friesian breed at the Animal Resources Research Center, Chungnam National University located at Cheongyang, Chungnam, South Korea. Milk com- ™ positions were measured by MilkoScan FT + (FOSS, Hilleroed, Denmark). Te total solids content of Camem- bert cheeses was determined by vacuum oven sand pan method in a vacuum drying oven (VOS-201SD, Eyela, Japan) at 70 °C for 24 h [11]. Fat content was measured by a Rose-Gottlieb method [12]. Protein content was meas- ured by a Kjeldahl method [13]. Starter culture Starter cultures used were the DVS (Direct Vat Set) cultures composed of Lactococcus cremoris, Lactococ- cus diacetylactics, Lactococcus lactics, Leuconostoc mensenteroides (CH-N11, Chr-Hansen Co., Denmark). Te Penicillium candidum (Chr-Hansen Co., Denmark) Fig. 1 Preparation procedure of the Camembert cheeses with the four types of salts including refned salt, baked refned salt, sun‑dried was added on the surface of the experimental Camem- salt, and Himalayan rock salt bert cheeses. Bae et al. Appl Biol Chem (2020) 63:66 Page 3 of 12 Water soluble nitrogen (WSN) for sugars, e.g., lactose, glucose, galactose, fructose, and Changes in WSN of cheeses were measured to estimate sucrose and for organic acids, e.g., acetic acid, oxalic acid, the extent of protein degradation during ripening period citric acid, lactic acid, propionic acid, butyric acid, and [18, 19]. Te cheese samples were homogenized with a succinic acid used for the experiments were purchased homogenizer (ULTRA TURRAX T25, Janke & Kunkel, from Sigma-Aldrich Co. in Germany [16]. IKA Labortechnic, Germany) with sterilized water and cheese at a ratio of 4: 1 (20 g cheese and 90 mL sterilized Fat extraction water) and centrifuged at 1800 × g (Mega 17R, Hanil Sci- Five grams of cheese sample were mixed with 25 ml ether ence Industrial, Korea). After centrifugation for 30 min., for fat extraction, and shaken for 3 h at 30 °C/200 rpm the supernatant was fltered through Whatman No.2, and [20]. Te supernatant of fat extract was decanted, and 2.5 ml of reagent A (12% trichloroacetic acid) and 0.5 ml concentrated using nitrogen gas to a volume of 1/16. distilled water was added to supernatant [19]. Te mix- ture was allowed to stand at room temperature for 20 min Volatile fatty acid determination and the supernatant was fltered through Whatman Changes in fatty acid profles during cheese ripening No.