Over a two year period, 1704 samples of half udder milk of 213 Paska sheep from three herds, were collected monthly throughout lactation to estimate if 700x10 3 somatic cells/mL could be the threshold value for healthy sheep. The influence of herds, stage and number of lactation on somatic cell count (SCC) was included. The estimated mean value for SCC was 143,4x10 3 /mL. Only 7,74% (n=58) samples were >700x10 3 SCC/mL. Regarding the causative organism, 12 samples were positive to Staphylococcus aureus, 14 to Micrococcus spp., 4 to both Staphylococcus aureus and Micrococcus spp. and 1 to Streptococcus D, respectively. Therefore, threshold value in diagnosis of subclinical mastis could be 700 x10 3 /mL.
Milk yield of 20 single suckled ewes from Chios and some Egyptian oasis sheep (Farafra) in additional to 15 twins suckled of both ewes were estimated over two lambing seasons. The average of total milk yield, milk yield during suckling period (8 weeks), after weaning and lactation length of Chios, were 98.49, 69.50, 29.00 kg and 132.41 days while they were 38.67, 37.10, 1.57 kg and 70.59 days in Farafra ewes, respectively. Breed had significant (p < 0.01) effect on total milk yield. Correlation coefficient between body weight of the ewe at lambing and total milk yield was 0.56 (p<0.01). The average fat percentage was 7.1 and 6.00 in Chios and Farafra milk, respectively. Breed had no significant effect on fat percent. The average total solids percentage was 17.7 and 17.6 in Chios and Farafra milk, respectively. Egyptian Oasis sheep (Farafra) as most Egyptian sheep are non dairy sheep. Introduction Chios sheep were imported from Cyprus in 1984 by Ministry of Agriculture. This work aimed to study the milk yield and its composition of Farafra ewes compared to Chios ewes.
The aim of this study is to evaluate milking characteristics and udder morphology during machine milking in Istrian dairy crossbreed ewes. The analyzed data belong to a total of 63 Istrian dairy crossbreed ewes (twelwe crosses with 75% Istrian and 25% Awassi, IAI; fourteen crosses with 25% Istrian, 25% Awassi and 50% East Friesian, IAEF; and thirty-seven crosses with 50% Istrian and 50% Awassi, IA). Milking time, milk yield, peak flow rate and average flow rate were measured during early, mid and late lactation. From the analyses performed, it can be concluded that IAEF Istrian dairy crossbreed has the highest milk production, average, peak flow rate and good udder shape, although all Istrian crossbreed ewes are well adapted to machine milking.
A supplement enriched in linseed (SEL) was assayed in the ewes' diet. During a three-month period bulk milk samples were collected every week from two different ewe herds and the fatty acid profile in milk fats was thoroughly monitored. The milk yield and main compounds were not affected by adding a SEL, whereas significant increases in C18:0, C18:1, C18:2 and C18:3 were observed during the period of supplementation. Conjugated linoleic acid (CLA) in milk fat increased and this increase was highly correlated to trans vaccenic acid (TVA) levels.
Physico-chemical interactions, such as those produced by solubility of aroma compounds in various aqueous solutions from -10 to +25°C were measured by the mutual solubility method. The influence of both the nature and concentration of substrates on solubility was studied using aqueous solutions of various substrates (polysaccharides, disaccharides and monosaccharides, linear polyols) from 0 to 57.5% (w/w). Aroma solubility in water decreased as hydrophobicity increased. Among compounds having the same carbon-atom number in their structure, solubility decreased as follows: aldehyde>methyl ketone> alcohol> ethyl ester. Aroma solubility in various aqueous solutions decreased as substrate concentration increased, being more pronounced with polyol solutions than with polysaccharide ones. The temperature effect showed an unexpected behaviour on aroma solubility: from -10 to -5°C, solubility increases; then from -5 to +4°C, solubility decreases. From +4 to +25°C, solubility increases once again, being the same for all the compounds in all media and concentrations.
Dynamic rheological techniques can aid the understanding of the factors contributing to ice cream structure, though the data obtained differs from that deduced from destructive techniques. Studies have shown that ice cream systems are both strain- and frequency-dependent.Chocolate ice cream is normally more viscous than the equivalent vanilla ice cream during mix preparation and has more body on freezing. Ice creams were prepared with and without cocoa solids and frequency sweeps were made from 0.1 to 100 Hz at 0.1% strain. With rapidly frozen ice creams, both G' and G" increased in the presence of cocoa solids.Comparison of mixes made with and without low-fat cocoa powder or non-gelatinizing starch demonstrated a similar relationship, with higher apparent viscosities in those mixes containing either cocoa powder or the starch. The results were consistent with the cocoa particles adding to the effect of the fat globules in increasing viscosity.
Health and wellbeing are linked inexorably to good food. Scientific research is now recognizing the challenges of providing diets to individuals that improve health beyond simply providing adequate nutrients. Few foods can be said to be as successful in providing the combination of delight and a sense of wellbeing as ice cream. However, the caloric content of ice cream and the content of saturated fats are considered by nutritionists to be a nutritional liability to consuming ice cream in large quantities. Nevertheless, before modifying what is considered to be one of the world's most delightful foods it is important to understand all of its functional and health properties. Ice cream is a dairy product and derived from milk. Milk evolved under the Darwinian selective pressure to nourish growing mammals and a new generation of scientific techniques are discovering what such evolutionary pressure produced. Milk provides nutrients and biologically active molecules and also communicates chemically between the maternal mammary epithelia and the infant's gastrointestinal system, actively directing and educating the immune, metabolic, sensory and microflora systems within the infant, enhancing the absorption of valuable nutrients and simultaneously protecting the intestine from toxins and pathogens. In discovering how milk achieves this, nutritionists are gaining a host of new molecular targets to design foods and clinical products. In many aspects ice cream provides values to an overall diet that are consistent with health and wellbeing. As nutrition moves towards a model of more personalized diet and health, each of us will learn just how much ice cream is optimal.
There is a wide range of antecedents about the use of whey in ice cream formulation. Whey and whey products have been used successfully in ice cream and frozen desserts for years. However, there are no international standards for the use of whey ingredients in ice cream. In Argentina, The Codigo Alimentario Argentino doesn't have any limitation about the use of this ingredient. In addition, it doesn't have minimal levels for protein or total solids content in ice cream. Sweet whey has recognized functional properties, results in superior finished product, improves freeze/thaw stability and nutritional aspects and reduces ingredient costs. The whey products most often used in ice cream include sweet whey, reduced-lactose whey, demineralized whey, modified whey, whey protein concentrate and whey protein isolate. Typical formulations using sweet whey include a 2.5% content in an ice cream with at least 38% total solids. Some considerations should be taken when formulating ice cream with whey products. The total lactose must be lower than 7.5% of total mix, in order to minimize lactose crystallization, which produces sandiness in the ice cream. The impact of the salty flavor of added whey should be taken into account at the time to define the product's saborization. In our case, the goal was to obtain a frozen dessert, which by local legislation is ice milk, with at least 1.5% of milkfat and 6.0% of milk solids-not-fat (MSNF), manufactured with the highest rate of sweet whey. The research was oriented to a product to be commercialized in supermarkets, with high rotation and short shelf life, with a low price and without brand costs. In that way, different formulations were evaluated, paying attention to the balance of the milk ingredients in use: cream, whole milk powder and sweet whey powder. We want to obtain a consumer-acceptable product with the lowest cost. In the acceptability parameters of the sensory assays we have included hedonic descriptive trays in order to detect the main flaws of this kind of formulation, which are sandiness and salty flavor. After a lot of assays, we've obtained a formulation that, in a first step, has been tested by an untrained sensory panel, against the product of our company that we want to replace. As the selling price of the new product was defined, it was compared to other brands of the same market segment. The acceptability ratio of the new product was very high, and the market answer was positive. In fact, this development has been sold by many supermarkets in our country for two years, with great success. The final conclusion is that it is possible to obtain a low-cost product, with good acceptability, by a formulation optimization that gives the chance to use sweet whey as a principal source of MSNF.
Classic ice cream textbooks from 40-50 years ago describe ingredients, formulations, manufacturing processes, equipment and product quality defects that are not unlike those of today. Despite the immense number of new products that are available in the market today, one might argue that there have been very few paradigm shifts in ice cream science and technology. However, is this a fair argument? Certainly there have been tremendous advances in understanding of the chemistry and physics of ice cream. There have also been more than just subtle shifts in ingredients, with more controlled use of non-dairy fats, milk protein ingredients, starch hydrolysate sweeteners and other sucrose alternatives, and stabilizing and emulsifying agents. Processing advances have included sophisticated, automated continuous freezers with exact control of overrun and dosing of particulate ingredients, sophisticated processing technology for manufacture of hand-held impulse products, and rapid hardening equipment.
The nature of the structural attributes of ice cream determines physical properties like hardness and melting rate. Structural attributes include properties of the air phase (overrun and air cell size distribution), ice phase (ice phase volume and ice-crystal size distribution), fat phase (total fat content, fat-globule size distribution and extent of fat destabilization) and the continuous phase (viscosity and gel formation). These structural elements are developed during manufacture and storage of ice cream through control of the formulation and process conditions. An understanding of the effects of these structural attributes is needed to better control the quality of ice cream.
Ice cream is considered merely as a food for enjoyment and its nutritional composition is not so relevant as long as ice cream consumption is restricted to a limited number of occasions. In view of the raised attention of the nutritional value of foods and the increased popularity of functional foods, one may ask the question whether ice cream is a suitable matrix for added value in the nutrition area. Ice cream consumption levels vary widely over countries and in those countries where the level of consumption is considerable and where weight-management problems are highly prevalent, the main challenge of the ice cream business is to make available to consumers low-caloric ice cream by replacing fat and sugar in the product, while maintaining the sensory properties.
Retail-manufactured ice cream samples formulated with 8% fat (milk cream) were produced in triplicate in a batch freezer, either with or without mix homogenization (16MPa) and ageing (24h). For comparison, ice cream samples formulated with 8% vegetable fat (coconut oil) were also produced in triplicate using both aged and non-aged homogenized mixes. Fat-globule-particle size distribution and the kinetics of protein desorption during mix ageing were investigated together with ice cream overrun, firmness, free-fat and melting properties.When homogenization was not applied, as traditionally done by artisan ice cream producers, the level of adsorbed protein and the physical characteristics of cream-based ice cream were not affected by mix ageing. On the contrary, ageing of both cream and coconut oil homogenized mixes caused protein desorption, and free-fat reduction and melting-rate increase in ice creams.The level of adsorbed proteins per unit fat-globule area was almost double when vegetable fat was used in homogenized mixes. However, those proteins were quickly desorbed during mix ageing. The protein desorption phenomenon was quite less evident in cream-based formulations.No significant effect of mix ageing and homogenization were observed on ice cream overrun and firmness.
The influence of different parameters on the quality of bottom-filled moulded ice cream has been studied. The parameters-investigated were different drawing temperatures, overruns, amounts of added locust bean gum, different types of mono-diglycerides and freezing points of the ice cream mix. It was found that decreasing the drawing temperature from the ice cream freezer produced a creamier, more warm-eating ice cream, and a higher degree of fat agglomeration (SEF), which increased the melting resistance of the ice cream. It also gave smaller ice crystals in the ice cream, which made the ice cream softer. The hardness of the ice cream could be increased by either raising the freezing point of the mix or decreasing the overrun. The type of mono-diglyceride (saturated/unsaturated) used in the ice cream and addition of stabilizer (locust bean gum) had no significant effect on the hardness of the ice cream. Increasing the overrun of the ice cream gave a more warm-eating and creamy product with lower body and increasing melting resistance. The addition of a stabilizer (locust bean gum) increased the mix viscosity and body of the ice cream. Locust bean gum also increased the melting resistance and slowed down the growth of the ice crystals. Compared to saturated mono-diglyceride, unsaturated mono-diglyceride provided a creamier, more warm-eating ice cream. It gave increased melting resistance but had no significant effect on ice-crystal growth compared to saturated mono-diglyceride. Decreasing the freezing point of the mix gave softer ice cream, but had a detrimental effect on heat-shock stability, resulting in faster growth of the ice crystals during heat shock. It also decreased the melting resistance of the ice cream.
Although the composition of the fat interface in ice cream and the factors affecting it have been well studied, the same is not true for the air interface. It is believed that the air interface is formed during foaming by proteins, perhaps in competition with monoglycerides, and that fat globules, perhaps partially coalesced, also adsorb to the air interface providing stability. However, it is difficult to study the actual role of individual proteins and monoglycerides because techniques used for quantifying fat interfaces are not easily transferable to air interfaces. We have used two techniques to examine protein interactions with air bubbles. The first involves foaming of model milk protein solutions and quantifying protein composition in the foam phase by capillary zone electrophoresis. Caseins were shown to have a higher enrichment ratio in the foam phase than whey proteins and beta-casein had the highest enrichment. Environmental factors affecting protein foaming and competition with monoglycerides were studied. The second technique involves protein labeling with immuno-gold antibodies and localization by transmission electron microscopy after freeze-substitution of the sample. Both β-casein and β-lactoglobulin have been studied. Monoglycerides have been seen to reduce protein adsorption at interfaces.
Incompatibility between milk proteins and polysaccharide stabilizers, especially in soft-serve ice cream mixes with long shelf life, leads to macroscopic phase separation during storage. The inclusion of K-carrageenan in levels above 0.015% is effective in avoiding these phenomena. Analysis of different whey to casein ratios (at constant protein concentration) showed that as casein proportion diminishes, instability of the mix, that is, rate and degree of separation, decreases. Viscosity does not relate to stability since mixes with higher whey proportion (better stability) are less viscous. K-carrageenan is thought to interact electrostatically with K-casein and the helical form of K-carrageenan is also known to form weak gels at very low concentration. Either or both mechanisms may be involved. Stable systems still exhibit microscopic phase separation.
The influence of emulsifiers (mono- and diglycerides) on heatshock stability of ice cream with 8%, fat produced with different levels of overrun -60'%, 100% and 140% - was studied. Size distribution of air bubbles and ice crystals, air-cell structure, melting resistance, solvent extractable fat, whiteness and sensory properties in fresh ice cream samples and heat-shocked samples were studied. Emulsifiers increased heat-shock stability and melting resistance. Unsaturated emulsifiers (uMG) gave better melting resistance than saturated emulsifiers (sMG). Emulsifiers increased air-bubble stability and gave a finer air-bubble distribution. High air content protected ice cream from ice crystal growth in the presence of emulsifiers. Low air content gave inferior melting resistance.The effect of sMG and uMG was evaluated in low-fat (1%) and no-fat (0%) ice cream with results showing that uMG had better effects on air stability than sMG. This was confirmed by transmission electron microscopy of air bubble surface stabilized by multilayers of large plate-formed fat crystals with uMG and more fragile air-bubble surfaces with thinner layers of smaller fat crystals with sMG. For the same reason ice cream with uMG showed much better meltdown stability than those with sMG.
