Investigating Structural Defects in Extra Hard Cheese Produced from Low-Temperature Centrifugation of Milk

The present study investigated some physico-chemical and microbiological traits of 20-month ripened hard cheeses produced from low-temperature high-speed centrifuged raw milk that developed a structural defect consisting of eyes or slits in the paste. Cheeses obtained using the same process and that did not develop the defect were used as controls. The colour, texture, moisture, water activity, proton molecular mobility, microstructure, extent of proteolysis, and viable microorganisms have been evaluated in all the cheese samples, and the significant differences between the defective and non-defective cheeses have been critically discussed. At a microstructural level, the defects caused fat coalescence and an unevenly organised protein matrix with small cracks in the proximity of the openings. The different fat organisation was correlated to a different transverse relaxation time of 1H population relaxing at higher times. The textural and colour features were not different from those of the control cheeses and were comparable with those reported in the literature for other long-ripened hard cheeses. On the other hand, the defective cheeses showed a higher moisture level and lower lactobacilli and total mesophilic bacteria concentrations, but the microbial origin of the defect remains an open hypothesis that deserves further investigation.

New Insights into Cheese Microstructure

Microscopy is often used to assist the development of cheese products, but manufacturers can benefit from a much broader application of these techniques to assess structure formation during processing and structural changes during storage. Microscopy can be used to benchmark processes, optimize process variables, and identify critical control points for process control. Microscopy can also assist the reverse engineering of desired product properties and help troubleshoot production problems to improve cheese quality. This approach can be extended using quantitative analysis, which enables further comparisons between structural features and functional measures used within industry, such as cheese meltability, shreddability, and stretchability, potentially allowing prediction and control of these properties. This review covers advances in the analysis of cheese microstructure, including new techniques, and outlines how these can be applied to understand and improve cheese manufacture.

Polyethylene Migration from Food Packaging on Cheese Detected by Raman and Infrared (ATR/FT-IR) Spectroscopy

For multiple years, food packaging migration has been a major concern in food and health sciences. Plastics, such as polyethylene, are continuously utilized in food packaging for preservation and easy handling purposes during transportation and storage. In this work, three types of cheese, Edam, Kefalotyri and Parmesan, of different hardness were studied under two complementary vibrational spectroscopy methods, ATR-FTIR and Raman spectroscopy, to determine the migration of low-density polyethylene from plastic packaging to the surface of cheese samples. The experimental duration of this study was set to 28 days due to the degradation time of the selected cheese samples, which is clearly visible after 1 month in refrigerated conditions at 4 °C. Raman and ATR-FTIR measurements were performed at a 4–3–4–3 day pattern to obtain comparative results. Initially, consistency/repeatability measurement tests were performed on Day₀ for each sample of all cheese specimens to understand if there is any overlap between the characteristic Raman and ATR-FTIR peaks of the cheese with the ones from the low-density polyethylene package. We provide evidence that on Day₁₄, peaks of low-density polyethylene appeared due to polymeric migration in all three cheese types we tested. In all cheese samples, microbial outgrowth started to develop after Day₂₁, as observed visually and under the bright-field microscope, causing peak reverse. Food packaging migration was validated using two different approaches of vibrational spectroscopy (Raman and FT-IR), revealing that cheese needs to be consumed within a short time frame in refrigerated conditions at 4 °C.

Invited review: Crystals in cheese: More than a curiosity

Scientific interest in cheese crystals extends back more than a century. However, starting around the 1970s, industry interest, and interest on the part of cheese scientists, grew dramatically as changes in cheesemaking technology and market changes caused the presence of crystals in the marketplace to increase; advanced analytical capabilities enabled new crystalline species to be identified, their origins and causative factors to be elucidated, and their contributions to cheese texture to be better understood. It is now evident that a host of organic- and inorganic-based crystals occur in natural cheeses. Some crystals form preferentially at the surface of rindless or rinded cheeses, others in the irregular openings or spherical eyes that occur within the body of some cheeses, and still others embedded within the cheese matrix. It is also evident that crystals may profoundly influence cheese texture, both as a direct consequence of their abundance, size, shape, and hardness, and as an indirect result of cascading physiochemical events initiated by crystal formation. Consumer response to increased incidence of crystals in the marketplace has been mixed. On the one hand, surface crystals of calcium lactate pentahydrate on Cheddar cheese came to be viewed quite negatively in some markets, often being mistaken for mold growth and spoilage. This triggered industry concern and led to considerable research to determine the underlying causes and to develop strategies to limit or prevent calcium lactate pentahydrate formation. At the same time, other forms of crystallization increasingly came to be viewed as positive features in the growing market dedicated to artisanal and traditional cheeses, giving rise to a bifurcated consumer response to cheese crystals that is evident today. Traditional artisanal cheesemakers perhaps have the most to gain from advances in cheese-crystal research. Traditional artisanal cheeses rely heavily on stories that are weaved around their identity to create uniqueness and add value. A challenge and opportunity for these cheesemakers in the United States and globally will be to translate the fascinating science of their cheese crystals into engaging narratives that capture the imagination, add value to their cheese, and enhance the enjoyment of their cheese by consumers.

Composition, source, and influencing factors of white spots formation in soybean paste

White spots are commonly found in bean-based fermented food, which will significantly lower the product quality. This study aimed to analyze the composition of white spots and further reveal the source and influencing factors of white spots in bean-based fermented food using soybean paste as study model. The results showed that white spots were mainly composed of 40.96% free tyrosine and 37.94% tyrosine in combination form. During soybean paste fermentation, tyrosine was found to be produced by the actions of proteolytic enzymes secreted by Aspergillus oryzae 3.042 instead of the microbial metabolism and the excessive accumulation of tyrosine in soybean paste led to the formation of white spots. Among all influencing factors, high temperature treatment favored the formation of white spots. The existence of soy peptone and phenylalanine would postpone the precipitation of tyrosine while promoting the aggregation of the tyrosine precipitation. Field emission scanning electron microscope analysis showed that tyrosine would accumulate around the soybean protein particles and treatment at 120 °C would disrupt the structure of tyrosine-protein complex. Based on the above results, we proposed that treatment of soybean paste at temperature lower than 80 °C was the current practically applicable method to control the formation of white spots in soybean paste. PRACTICAL APPLICATION: This study developed a new idea to understand the composition and formation of white spots in soybean paste, which would provide guidance for prevention and control of white spots during the production of soybean paste for manufacturers and researchers.

Applicability of Confocal Raman Microscopy to Observe Microstructural Modifications of Cream Cheeses as Influenced by Freezing

Confocal Raman microscopy is a promising technique to derive information about microstructure, with minimal sample disruption. Raman emission bands are highly specific to molecular structure and with Raman spectroscopy it is thus possible to observe different classes of molecules in situ, in complex food matrices, without employing fluorescent dyes. In this work confocal Raman microscopy was employed to observe microstructural changes occurring after freezing and thawing in high-moisture cheeses, and the observations were compared to those obtained with confocal laser scanning microscopy. Two commercially available cream cheese products were imaged with both microscopy techniques. The lower resolution (1 µm/pixel) of confocal Raman microscopy prevented the observation of particles smaller than 1 µm that may be part of the structure (e.g., sugars). With confocal Raman microscopy it was possible to identify and map the large water domains formed during freezing and thawing in high-moisture cream cheese. The results were supported also by low resolution NMR analysis. NMR and Raman microscopy are complementary techniques that can be employed to distinguish between the two different commercial formulations, and different destabilization levels.

Impact of Extending Hard-Cheese Ripening: A Multiparameter Characterization of Parmigiano Reggiano Cheese Ripened up to 50 Months

Extending ripening of hard cheeses well beyond the traditional ripening period is becoming increasingly popular, although little is known about the actual evolution of their characteristics. The present work aimed at investigating selected traits of Parmigiano Reggiano cheese ripened for 12, 18, 24, 30, 40 and 50 months. Two cheeses per each ripening period were sampled. Although moisture constantly decreased and was close to 25% in 50-month cheeses, with a parallel increase in cheese hardness, several biochemical changes occurred involving the activity of both native and microbial enzymes. Capillary electrophoresis demonstrated degradation of α_s1- and β-casein, indicating residual activity of both chymosin and plasmin. Similarly, continuous release of free amino acids supported the activity of peptidases deriving from lysed bacterial cells. Volatile flavor compounds, such as short-chain fatty acids and some derived ketones, alcohols and esters, evaluated by gas chromatography with solid-phase micro-extraction, accumulated as well. Cheese microstructure was characterized by free fat trapped in irregularly shaped areas within a protein network, with native fat globules being no longer visible. This study showed for the first time that numerous biochemical and structural variations still occur in a hard cheese at up to 50 months of aging, proving that the ripening extension deserves to be highlighted to the consumer and may justify a premium price.

Size, shape, and identity of surface crystals and their relationship to sensory perception of grittiness in soft smear-ripened cheeses

Soft smear-ripened cheeses undergo extensive surface crystallization and radial demineralization of calcium, magnesium, and phosphorus, which likely contributes to radial softening during ripening. Furthermore, anecdotal evidence suggests that grittiness is a common characteristic of smear-ripened cheeses. The primary aims of the present study were to evaluate the intensity of perceived grittiness while assessing other key sensory attributes in US artisanal and European protected designation of origin smear-ripened cheeses, and to relate perceived grittiness to the size, shape, and identity of crystals present in the cheese surface smears. Fully ripened wheels of 24 different varieties of smear-ripened cheeses, 16 produced in the United States and 8 in the European Union, were obtained from retail sources. A trained sensory panel (n = 12) was employed to evaluate intensity of grittiness. Crystals present in the cheese smears were identified by powder X-ray diffractometry and polarized light microscopy, and further evaluated in polarized light microscopy micrographs by image analysis for size and shape characteristics. Mean sensory scores for the 24 cheeses ranged from no perceived grittiness to easily identifiable grittiness. Surface crystals included ikaite, struvite, calcite, and brushite, and mean crystal length and area ranged among cheeses from 27 to 1,096 μm, and 533 to 213,969 μm², respectively. Panel threshold for grittiness occurred at a mean crystal length of about 66 μm and mean crystal area of about 2,913 μm². Cheeses with mean values at or below these thresholds displayed negligible perceived grittiness. In contrast, for cheeses with mean values above these thresholds, the mean sensory scores for grittiness were highly correlated with mean crystal length and crystal area (r = 0.93 and 0.96, respectively). Results suggest that surface crystals in soft smear-ripened cheeses influence sensory perception of texture in complex ways that likely include radial softening and grittiness development. A better understanding of factors that govern surface crystal formation may lead to improved control over crystallization and more consistent cheese texture.

Impact assessment of traditional food manufacturing: The case of Grana Padano cheese

The dairy sector is recognised as one of the most impacting agricultural activities. In Italy approximately 24% of cow's milk is destined to Grana Padano, a Protected Designation of Origin long ripening cheese. The Grana Padano production has increased by 10% in the last decade and approximately reached 183,000 t in 2015. Around 38% of this production is exported to Germany, US, France and to the rest of the world. This study evaluated the environmental impact of production of Grana Padano, through a "cradle to cheese factory gate" Life Cycle Assessment. The study involved an Italian cheese factory that produces about 3.6% of the total production of Grana Padano cheese and a group of 5 dairy farms, chosen among the farms that sold all milk produced to the cheese factory. The functional unit was 1 kg of Grana Padano cheese 12-month ripened. Environmental impacts of co-products: whey, cream, butter and buttermilk were also evaluated. Two sensitivity analyses were conducted: the first one had the aim to explore the effect of different allocation methods based on dry matter content, economic or nutritive value of cheese, respectively; the second one considered the variation of the impacts of milk production and its effect on cheese environmental impact. Milk production phase gave the most important contribution to the environmental impact of cheese, with a percentage of 93.5-99.6% depending on the impact category. Excluding milk production from the system boundary, milk transport and use of electricity were the main responsible of the environmental impact of cheese-making process. The climate change impact for the production of 1 kg Grana Padano was 10.3 kg of CO₂ eq, using a dry matter allocation method, while 16.9 and 15.2 kg of CO₂ eq adopting economic and nutritive value allocation methods, respectively.