Manufacture of Whey Protein Hydrolysates Using Plant Enzymes: Effect of Processing Conditions and Simulated Gastrointestinal Digestion on Angiotensin-I-Converting Enzyme (ACE) Inhibitory Activity.

Hydrolysis of proteins leads to the release of bioactive peptides with positive impact on human health. Peptides exhibiting antihypertensive properties (i.e., inhibition of angiotensin-I-converting enzyme) are commonly found in whey protein hydrolysates made with enzymes of animal, plant or microbial origin. However, bioactive properties can be influenced by processing conditions and gastrointestinal digestion. In this study, we evaluated the impact of three plant enzymes (papain, bromelain and ficin) in the manufacture of whey protein hydrolysates with varying level of pH, enzyme-to-substrate ratio and time of hydrolysis, based on a central composite design, to determine the degree of hydrolysis and antihypertensive properties. Hydrolysates made on laboratory scales showed great variation in the type of enzyme used, their concentrations and the pH level of hydrolysis. However, low degrees of hydrolysis in papain and bromelain treatments were associated with increased antihypertensive properties, when compared to ficin. Simulated gastrointestinal digestion performed for selected hydrolysates showed an increase in antihypertensive properties of hydrolysates made with papain and bromelain, which was probably caused by further release of peptides. Several peptides with reported antihypertensive properties were found in all treatments. These results suggest plant enzymes used in this study can be suitable candidates to develop ingredients with bioactive properties.

Effect of lactose standardization of milk using low-concentration factor ultrafiltration: Effect of reducing the lactose-to-casein ratio on the properties of milled-curd Cheddar cheese.

The pH of cheese is determined by the amount of lactose fermented and the buffering capacity of the cheese. The buffering capacity of cheese is largely determined by the protein contents of milk and cheese and the amount of insoluble calcium phosphate in the curd, which is related to the rate of acidification. The objective of this study was to standardize both the lactose and casein contents of milk to better control final pH and prevent the development of excessive acidity in Cheddar cheese. This approach involved the use of low-concentration factor ultrafiltration of milk to increase the casein content (∼5%), followed by the addition of water, ultrafiltration permeate, or both to the retentate to adjust the lactose content. We evaluated milks with 4 different lactose-to-casein ratios (L:CN): 1.8 (control milk), 1.4, 1.1, and 0.9. All cheesemilks had similar total casein (2.3%) and fat (3.4%) contents. These milks were used to make milled-curd Cheddar cheese, and we evaluated cheese composition, texture, functionality, and sensory properties over 9 mo of ripening. Cheeses made from milks with varying levels of L:CN had similar moisture, protein, fat, and salt contents, due to slight modifications during manufacture (i.e., cutting the gel at a smaller size than control) as well as control of acid development at critical steps (i.e., cutting the gel, whey drainage, salting). As expected, decreasing the L:CN led to cheeses with lower lactic acid, residual lactose, and insoluble Ca contents, as well as a substantial pH increase during cheese ripening in cheeses. The L:CN ratio had no significant effect on the levels of primary and secondary proteolysis. Texture profile analysis showed no significant differences in hardness values during ripening. Maximum loss tangent, an index of cheese meltability, was lower until 45 d for the L:CN 1.4 and 0.9 treatments, but after 45 d, all reduced L:CN cheeses had higher maximum loss tangent values than the control cheese (L:CN 1.8). Sensory analyses showed that cheeses made from milks with reduced L:CN contents had lower acidity, sourness, sulfury notes, and chewdown cohesiveness. Standardization of milk to a specific L:CN ratio, while maintaining a constant casein level in the milk, would allow Cheddar cheese manufacturers to have tighter control of pH and acidity.

Chemical Composition, Fatty Acid Profile and Sensory Characteristics of Chanco-Style Cheese from Early Lactation Dairy Cows Fed Winter Brassica Crops.

Brassica crops such as kale and swede can be supplied to cow diets during winter, however little is known about the effects of feeding those forage brassicas to lactating cows on cheese nutritional characteristics of milk and cheese. This study evaluated the effect of including kale or swede in pasture-fed lactating dairy cow diets on chemical composition, fatty acid (FA) profile, and sensory characteristics of Chanco-style cheese. Twelve early-lactation cows were used in a replicated (n = 4) 3 × 3 square Latin square design. The control diet consisted of (DM basis) 10.0 kg of grass silage, 4.0 kg of fresh grass pasture, 1.5 kg soybean meal, 1.0 kg of canola meal, and 4.0 kg of cereal-based concentrate. The other treatments replaced 25% of the diet with swede or kale. Milk yield, milkfat, and milk protein were similar between treatments as were cheese moisture, fat, and protein. Swede and kale increased total saturated cheese FA while thrombogenic index was greater in swede, but color homogeneity and salty flavor were greater while ripe cheese aroma less than for kale. Kale or swede can be used in the diet of pasture-fed lactating dairy cows without negative effects on milk production, milk composition, or cheese composition. However, kale and swede increased total cheese saturated FA.

Changes in the chemical and in-vitro antihypertensive properties of sweet whey obtained from miniature fresh, Chanco and Gouda-style model cheeses.

This Technical Research Communication evaluated the influence of various cheese manufacture methods on the composition and in vitro antihypertensive activity of sweet whey samples obtained from miniature models for fresh, Chanco and Gouda-style cheese processing using bulk-tank milks throughout a year. Raw milks from morning milking were standardized, pasteurized and used to obtain sweet whey using cheesemaking protocols for each variety on 200 g scale, as well the use of whey dilution at levels of 0, 15, 30 and 45% in Chanco and Gouda-style making. The composition of sweet whey obtained within each cheesemaking variety was similar among different timepoints of the year (P > 0.05), which was attributed to similar composition of milks and the use standardized cheesemaking protocols used for this study. As expected, the use of whey dilution led to sweet whey samples with reduced levels of total solids (P < 0.05), but they exhibited an improvement of the in vitro antihypertensive properties, which may be attributed to the formation of low-molecular weight bioactive peptides due to increased cheese making times. The results of this study suggest that modifying cheese manufacture protocols may have a direct impact on the bioactive properties of sweet whey. Future work will be required to identify and evaluate the feasibility to purify bioactive peptides obtained from sweet whey.

Rheological study of tannin and protein interactions based on model systems.

The interaction between wine tannins and saliva proteins is responsible for wine astringency perception, producing a depletion of salivary proteins and changes on oral friction. In sensorial terms, astringency is described as a dryness and puckering sensation in the mouth, which is related to the "structure" or "body" of red wines. However, these last descriptors, as structure or body, are perceived during wine tasting and commonly related to wine viscosity. To address these differences on sensory response, we hypothesize that tannin-protein interactions could be a key factor involved in the viscosity of red wines/saliva mixtures, just as they are for astringency. We used a rheological method to study the impact of tannin-protein interaction on the viscosity of model wine-saliva systems. Mixtures of model saliva based on mucin and typical astringent compounds, as commercial tannins and gallic acid, were evaluated for their rheological behavior. The viscometric flow of the fluid mixtures was determined, and subsequently, the viscosity was evaluated at a shear rate of 60 s-1 . It was observed that red wines/saliva mixtures exhibit non-Newtonian flow and ascending tannin doses led to an increase in the apparent viscosity. Nephelometric analysis demonstrate that tannin-mucin aggregates were formed, which suggests that these complexes were potentially responsible for the viscosity increases, modifying the rheological behavior of these mixtures. Results from this work propose that tannin-protein interactions are also involved in the underlying mechanism of thickness perception of red wines and rheology could be a complementary instrumental technique for wine mouthfeel characterization.

Effect of forage brassicas in dairy cow diets on the fatty acid profile and sensory characteristics of Chanco and Ricotta cheeses.

In humid temperate regions, forage turnip (Brassica rapa ssp. rapa) and forage rape (Brassica napus ssp. biennis) are common fodder crops used for dairy cattle during the summer season. However, there is little scientific information regarding the use of brassicas and their effect on the fatty acid (FA) profile in blood, milk, and milk products. The aim of this study was to evaluate the effect of forage brassica supplementation in dairy cows on the FA profile of blood plasma, milk, and cheese, and on the sensory characteristics of Chanco and Ricotta cheeses. Twelve multiparous dairy cows (Holstein Friesian) were housed and submitted to a 3 × 3 replicated (n = 3) Latin square design with 3 treatments (control, turnip, or rape) in 3 periods of 21 d each (14 d of diet adaptation and 7 d of measurements). The control diet consisted of 16.20 kg of grass silage (Lolium perenne), 2.25 kg of soybean bran, and 2.25 kg of commercial concentrate, all on a dry matter (DM) basis. In the treatments with forage brassicas, 24.15% of the total DM was replaced by turnip or rape; thus, they consisted of 12.25 kg of silage, 2.25 kg of soybean bran, 1.2 kg of concentrate, and 5 kg of turnip or rape (DM basis). A principal components analysis was performed on the results of the cheese sensory evaluation. Supplementation with turnip or rape modified the profile of FA in blood plasma and milk, increasing the saturated fraction, mainly short- and medium-chain FA, and decreasing the mono- and polyunsaturated FA. In the sensory evaluation, diet did not affect any of the 18 attributes evaluated. However, in the principal components analysis, cheeses made with milk from animals fed turnip and rape were differentiated by increased odor, flavor, spiciness, bitterness, and acidity. Overall, brassicas can be used as an alternative forage source with no negative effects on sensory characteristics of cheeses.

Effect of Feeding Cows with Unsaturated Fatty Acid Sources on Milk Production, Milk Composition, Milk Fatty Acid Profile, and Physicochemical and Sensory Characteristics of Ice Cream.

The objective of this study was to evaluate the effects of supplementation of dairy cows with different fatty acid sources (soybean oil (SO) and fish oil (FO)) on milk production, milk composition, milk fatty acid profile, and physicochemical and sensory characteristics of ice cream. During 63 days, fifteen Holstein cows averaging 198 ± 35 days in milk were assigned to three groups: control diet with no added lipid (n = 5 cows); and supplemented diets with SO (n = 5 cows; unrefined SO; 30 g/kg DM) or FO (n = 5 cows; FO from unrefined salmon oil; 30 g/kg DM). Milk production, milk fat, and milk protein were not affected by treatments. Saturated fatty acids in milk fat were decreased with SO and FO compared with control. C18:2 cis-9, cis-12 was increased with SO whereas C18:2 cis-9, trans-11, C20:3n-3, C20:3n-6, C20:5n-3, and C22:6n-3 were the highest with FO. Draw temperature and firmness were higher in SO compared to control and FO ice creams. Melting resistance was higher in FO compared with control and SO ice creams. Supplementation of cow diets with SO and FO did not have detrimental effects on milk production, or ice cream physicochemical and sensory characteristics.

Influence of milk pH on the chemical, physical and sensory properties of a milk-based alcoholic beverage.

The research reported in this Research Communication evaluates the effect of milk acidification on the physicochemical and sensory properties of Licor de Oro (or Gold Liqueur; LO), a traditional alcoholic beverage produced in Chiloé island, Chile, which is made by mixing milk acidified with lemon juice and alcohol at a ratio of 1.0:1.0, along with sugar and other spices. The mixture is stored for a couple of weeks and then filtered to obtain a product with a yellowish-transparent appearance, sweetness and acidic taste, milky and alcoholic notes. The lack of information regarding LO processing, mainly in the amount of acid added to the mixture, leads to products of highly variable quality. Thus, the objective of this study was to evaluate the effect of milk acidification on the physicochemical and sensory properties of LO. Raw milk was acidified using citric acid to six different pH values: 6.7 (control), 6.0, 5.3, 4.6, 3.9 and 3.2. These milk treatments were then used to make LO. A decrease of milk pH led to LO with higher levels of sensorial and titratable acidity. LO obtained at pH 6.7 and 6.0 had higher levels of total protein than other treatments, leading to excessive turbidity. In contrast, treatments made at pH ≤5.3 had a typical transparent appearance of LO. These results suggest that a minimum level of milk acidification is required to obtain LO with desired appearance and composition.