Semimoist Pet Foods

Semimoist pet foods are those pet foods that have moisture content in the range of 15%-50% by weight (Priegnitz, 1980 Parthasarathy, 2004). Semimoist pet foods represent more expensive products with more meat-like characteristics and better appearances as well as improved palatability as compared to dry pet foods. Semimoist pet foods tend to maximize the advantages of both dry and moist pet foods, while minimizing the disadvantages of both products. 

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Semimoist foods usually contain about 30% moisture and provide pets with a meat-like food. This meat-like appearance has been the primary basis for the popularity of semimoist pet foods. 

Similarly, those proteins can be combined with uncolored ingredients to imitate marbling and form pet foods with chunk-meat appearance. This processing is commonly used in semimoist pet foods. 

Propylene glycol is also an effective humectant, preservative, and stabilizer and is found in such diverse apphcations as semimoist pet food, bakery goods, food flavorings, salad dressings, and shave creams. Humectancy, or the capabiUty of retaining moisture in a product, is a result of the vapor—Hquid equihbria of the glycol—water system and can be estimated from tables provided by suppHers (27). 

Semi-gloss alkyd paint formulation, 18 6 It Semi-interpenetrating network (IPN) approaches, 10 436 Semi-IPN (interpenetrating polymer network) hydrogels, 13 733 Semikilled steels, 23 291 Semimoist pet foods, 10 849 Semipermanent cells, 14 228 Semiphorone, 14 583 Semiportable mri system, 23 860-861 Semiregenerative reforming operations, 25 166... 

Miscellaneous, dry sausage casings, semimoist pet foods, confectionery 0.05-0.30... 

A large twin-screw extruder that is capable of making 6.3-15 MT of aquatic feeds and pet foods per hour and requires 450 kW (600 hp) is shown Figure 11. A process flow chart for making dry-expanded or semimoist pet foods and aquatic feeds is shown in Figure 12. 

Figure 12. Process flow sheet for making dry expanded or semimoist pet foods, and aquatic feeds. Courtesy of Wenger Manufacturing, inc., Sabetha, Kansas.

The production process of semimoist pet foods is similar to that of dry pet foods. However, there are some major differences, as shown in Figure 11.4. Semimoist pet foods require less energy inputs for processing because of their unexpanded nature (bulk density of greater than 480 g/L). Some semimoist pet foods are low-temperature formed with little or no cooking steps involved ingredients such as humectants are selected to control the water activity. 

After mixing, preconditioned materials are discharged into an extruder. The final product characteristics are affected by screw and barrel profiles, screw speed, processing conditions (temperature, moisture content, etc.), raw material properties, and die/knife type. A single-screw extruder is used in 85%-90% of all semimoist pet food production. All equipment requires stainless steel construction due to low pH (4.0-4.5) of most formulas. The extrusion temperature is maintained... 

Expanded semimoist pet foods are alternative semimoist pet foods with enhanced appearance and palatability. Normally, the expansion of semimoist pet foods is difficult due to the high moisture content and predominance of non-expandable materials, snch as meat, sngar, and polyhydric alcohols. On the other hand, sngar is needed to provide stability to semimoist pet foods. Thns, it is generally difficnlt to obtain the desired expansion, while achieving the stability of semimoist pet foods. 

Bartsch (1977) formnlated sngarless, expanded semimoist pet foods that were microbiologically stable throngh the adjnstment of pH and the nse of an antimycotic agent in combination with varions ingredients, which helped expand and maintain the expanded strnctnre. The preferred pH was in the range of 4.6-S.6. 

S)ME Physicochemical Properties oe Semimoist Pet Foods AS Aeeected by Processing... 

Some alternative ingredients, such as low-molecular-weight polypeptides, could also help reduce the water activity of semimoist pet foods. Preferred sources of low-molecular-weight polypeptides are autolysates of protein sources such as fish and meat. The materials are acidified with lactic acid to a pH below... 

Color is an important property for pet foods. Semimoist pet foods offer a meat-like appearance, to which the red color contributes greatly. The stabilization of product color is sometimes problematic in semimoist pet food production. A reaction of animal protein sources with carbon monoxide, which causes the formation of color-stabilized protein sources, is used to generate color-stabilized semimoist pet foods with a heat-stable bright red color (Hood, 1978). 

The key variables influencing the color of semimoist pet foods are (1) the extent of saturation of carbon-monoxide-bonding sites, (2) the oxidation of iron in the meat protein, (3) the final concentration of meat or blood protein, and (4) the type of heat (dry or moist) and its process, which maintains the color of the carbon-monoxide-treated materials. The carbon monoxide treatment is indeed necessary to stabilize the color of the products (Hood, 1977). 

Moist pet foods are usually defined as pet foods having a meat-like character and a moisture content of 50% by weight or higher. The maximum allowable moisture couteut for moist pet foods is 78% by weight (AAFCO, 2003) the moisture couteut iu most moist pet foods is two to three times of that iu semimoist pet foods aud up to mauy times of that iu dry pet foods. 

Development of IM semimoist pet foods was discussed by Karel (1976), since it was considered to be sufficiently important to have application in... 

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