Influence of Brine Concentration, Brine Temperature, and Presalting on Early Gas Defects in Raw Milk Pasta Filata Cheese

Symposium review: The Mozzarella/pasta filata years: A tribute to David M. Barbano

In the decades that followed the end of World War II, Mozzarella cheesemaking in the United States grew steadily as the pizza restaurant established an ever-expanding footprint across America and beyond. By the 1980s, Mozzarella cheesemaking had attained unprecedented scales of production, yet even as new cheese plants were coming on line across the country and production capacities were reaching extraordinary levels, the scientific and technological knowledge base needed to standardize production schedules, control product quality, and maximize cheese yields and efficiency lagged far behind industry needs. It was within this historical context that David Barbano turned his systematic and meticulous research program toward the needs of the Mozzarella cheese industry during the 1980s. By the early 1990s, Barbano was leading a team of graduate students, post-docs, technical staff, and collaborators in a systematic evaluation of every step in the Mozzarella cheesemaking process. The end product of these studies was nothing less than the transformation of what had been (to a large degree) a poorly understood "black box" process into a precisely controlled make procedure that lent itself to precision tailoring of cheese functionality, tight control over manufacturing schedules and efficiency, and maximization of cheese yields. Barbano's international collaborators included research scientists from Italy, where Mozzarella originated. Working with them, Barbano led a systematic evaluation of the scientific and technological aspects of Ragusano cheese, a traditional Protected Designation of Origin pasta filata cheese from Sicily. In the process, Barbano's team demonstrated a new approach to traditional artisanal practices that merged both the art and science of cheesemaking, in effect combining the best of both worlds, toward the goal of sustaining traditional cheesemakers and the working landscapes that they support. Throughout all of these studies, Barbano's research led to innovations in cheesemaking technology (such as improved salting methods, preacidification treatments, and strategies to improve low-fat Mozzarella functionality) that have revolutionized the Mozzarella industry worldwide.

Early blowing in raw goats' milk cheese: gas production capacity of Enterobacteriaceae species present during manufacturing and ripening

The aim of this study was to identify the main Enterobacteriaceae species responsible for early gas blowing during curdling and the first week of ripening in raw goats' milk cheese. Two batches of raw goats' milk cheese were selected. One of them showed early blowing within the first 24 h of cheese ripening while the other showed no alteration. Although initial levels of Enterobacteriaceae were similar in defective and non-defective cheese, their dynamics (growth and disappearance rates of the species detected) were different. Klebsiella oxytoca and Enterobacter cloacae were the main species in the defective curd, whereas Buttiauxela spp. was predominant in normal curd. Hafnia alvei was the prevailing isolated species for both normal and defective cheese throughout the ripening process. The highest gas production was rendered by K. oxytoca and H. alvei, mainly isolated from curd and cheese. However, other species relevant in milk or curd, like Pantoea ssp. or Buttiauxela spp. were considered as low gas producers. The analysis of digitalized images of cheese showed that most of the cheese eyes were formed before the first week of ripening, although this process continued during maturation.According to the species found in the defective and non-defective cheese, their proportions at different ripening stages, their ability to produce gas and eye formation, K. oxytoca might be considered the most likely responsible for early blowing in raw goats' milk cheeses; while H. alvei increased the eyes number in the later stages of the ripening period.

Salt influence on surface microorganisms and ripening of soft ewe cheese

The effect of different brining treatments on salt uptake and diffusion during the first 30 d of ripening was determined in soft ewe cheese. Additionally, salt influence on surface microorganisms and physicochemical parameters was evaluated. Cheeses were placed into different brine solutions (14, 18 and 24°Bé) at 5 and 10 °C for 1, 2 or 3 h. Samples from rind, outer core and inner core were analysed at 0, 7, 15 and 30 d. Complete salt diffusion from rind to the inner core took about 15 d. The resulting salt gradient favoured the development of a pH gradient from the surface to the inner core. Salt concentration also had a significant effect on the growth of surface microorganisms (mesophiles, pseudomonads and halotolerants). However, mould and yeasts were not affected throughout ripening by the salt levels achieved. Brine salting by immersion for 3 h at 10 °C in 24°B brine was found to be the most suitable treatment to control pseudomonads in cheese rind, as spoilage microorganism.

Interaction of Brine Concentration, Brine Temperature, and Presalting on Salt Penetration in Ragusano Cheese

Thirty-one 3.6-kg blocks of Ragusano cheese were made on each of 6 different days (in different weeks) starting with a different batch of milk on each day. On d 1, 3, and 5, the cheeses were not presalted and on d 2, 4, and 6, all cheeses were presalted (PS). One of the 31 blocks of cheese was selected at random for analysis before brine salting (i.e., on d 0). The remaining 30 blocks were randomly divided into 2 groups of 15 blocks each; one group was placed in 18% brine (18%B) and the other group was placed in saturated brine (SB). For the 15 blocks within each of the 2 brine concentrations (BC), 5 blocks were placed in a brine tank at 12 degrees C, 5 at 15 degrees C, and 5 at 18 degrees C, and submerged for 24 d. The research objective was to determine the combined impacts (i.e., interactions) of PS the curd before stretching, BC (SB vs. 18%B), and brine temperature (BT; 12, 15, and 18 degrees C) on salt uptake, moisture content, and yield of Ragusano cheese. Although BC, BT, and PS each had their own separate impacts on salt uptake, there was little interaction of these effects on salt uptake when they were used in combination. The PS most quickly delivered salt to the interior of the cheese and was the most effective approach to salting for controlling early gas formation. There were strong separate impacts of BC, BT, and PS on cheese moisture content, moisture loss, and net weight loss, with BC having the largest separate impact on these parameters. Reducing BT reduced salt content and increased moisture, but the effects were small. The more important effect of reduced BT was to reduce growth of gas forming bacteria. The 18%B produced higher moisture, and less moisture and weight loss than SB. The effect of interactions of BC, BT, and PS on moisture loss and net weight loss were small. To achieve the maximum benefit from the various approaches to salting for controlling early gas formation in Ragusano cheese, PS combined with slightly lower BT (i.e., 15 degrees C instead of 18 degrees C) should be used. Although using 18%B instead of SB did increase salt uptake, the point at which improved salt uptake occurred due to use of 18%B did not provide benefit in prevention of early gas formation, as reported separately. However, use of 18%B instead of SB provided a 9.98% increase in cheese yield due to reduced moisture loss during brining; this would be very attractive to cheese makers. The increase in yield needs to be balanced against the risk of growth of undesirable bacteria in the 18%B and the creation of another cheese quality defect.

Composition, Microstructure, and Surface Barrier Layer Development During Brine Salting

The goal of this study was to characterize the changes in chemical composition, porosity, and structure that occur at the surface of a block of brine-salted cheese and their relationship to the rate at which salt is taken up from the brine. To create a difference in composition, salt uptake, and barrier layer properties, identical blocks of Ragusano cheese were placed in saturated and 18% salt brine at 18 degrees C for 12 d. The overall moisture content and porosity decreased, whereas salt and salt in moisture content increased near the surface of blocks of brine-salted Ragusano cheese for all treatments. The general appearance of the microstructure of the surface of the blocks of brine-salted cheese was much more compact than the microstructure 1 mm inside the block at both brine concentrations. Large differences in porosity of the barrier layer were produced by brine-salting cheese in 18% vs. saturated brine, with cheese in saturated brine having much lower porosity at the surface and taking up much less salt during brining. The macro network of water channels within the microstructure of the cheese was less open near the surface of the block for cheese in both saturated and 18% brine after 4 d. However, no large differences in the size of the macro channels in the cheese structure due to the difference in brine concentration were observed by scanning electron microscopy. It is possible that the shrinkage of the much smaller pore structure within the casein matrix of the cheese is more important and will become more limiting to the rate of salt diffusion. Further microstructure work at higher resolution is needed to answer this question. The calculated decrease in porosity at the exterior 1-mm portion of the block was 50.8 and 29.2% for cheeses that had been in saturated vs. 18% brine for 12 d, respectively. The difference in brine concentration had a very large impact on the salt in moisture content of the cheese. The exterior of the cheese in 18% brine reached a salt in moisture content almost identical to that of the brine very quickly (17.3% at 4 d), whereas the salt in moisture content at the surface of the cheese block in saturated brine was only 11.9% at 4 d. There appears to be some critical concentration of salt in brine above which there is a large negative impact on salt uptake due to the creation of a barrier layer at the surface of the block of cheese.