Processing damage to protein food

Thermodynamic study of canned mince meat and fish in metal cans during 30 months storage

Long storage period for the meat and fish cans of 30 months was presented. The provide investigation aims to found thermodynamic stability in mackerel in tomato sauce and finely ground pork minced meat. During the storage period a decrease in pH in two types of cans were seen. pH values for mackerel in tomato sauce and for finely ground pork minced meat cans were measured between 6.2±0.19 to 4.8±0.22 and 5.8 ±0.24 to 3.9±0.17 in the starting to the end of storage, respectively. Determined absorption is used to calculated equilibrium constant, Gibbs free energy (ΔG), enthalpy (ΔH) and entropy (ΔS). For mackerel in tomato sauce ΔG exhibit value -8.33±0.07 kJ.mol−1 and for finely ground pork -6.79±0.09 kJ.mol−1. Microscopic examinations were performed and the size of the particles was determined. In measurements in mackerel in tomato sauce the sizes are between 25±0.79 to 62±1.28 μm and for finely ground pork minced meat the particle sizes are between 32±1.12 to 89±2.48 μm in the investigation period. Based on the experiment, both types of canned food are defined as thermodynamically stable after negative Gibbs energies observations, but canned fish is defined as more stable and may have a longer stored.

Fish-protein hydrolysate as a substitute for milk protein in calf feeding

Two milk replacers identical in composition except for the protein source, which was either fish-protein hydrolysate (FPH) or dried skim milk, were offered either twice or four times daily to castrated British Friesian male calves in four ratios: 100 FPH 0 Milk; 67 FPH 33 Milk; 33 FPH 67 Milk and 0 FPH 100 Milk. Concentrates and hay were offered ad libitum, and the calves were weaned at 42 days of age. Feed intake and calf live weight were recorded to 100 days of age.

There were no differences in growth rate up to weaning due to frequency of feeding. Up to 67% FPH there were no differences in growth rate but calves on the 100% FPH diet showed a 40% depression in growth compared with the other three levels. Up to 100 days there was no apparent effect of treatment on live-weight gain, but only differences of 12 to 13% would be significant.

The results indicate that at least two-thirds of the milk protein could be replaced by FPH. The need for further work using dried material and FPH from other species is discussed.

A comparison of undried and dried fish-protein hydrolysate as a protein source for calf milk replacers

Milk replacers in which skim milk protein (SMP) was replaced in various proportions by undried or dried fish protein hydrolysate (FPH) were offered twice daily to British Friesian male calves. Various proportions of fish protein and milk protein in the diets were obtained by mixing replacer made from SMP with replacers made from undried and dried FPH respectively. The ratios were: 100 FPH, 0 SMP; 67 FPH, 33 SMP; 33 FPH, 67 SMP; and 0 FPH, 100 SMP. Calves were offered the milk replacers only to a maximum of 5 1 per day until 28 days when concentrates and hay were offered ad libitum. The calves were weaned after 42 days. Feed intake and live-weight gain were recorded for 84 days.

There was a marked decrease in performance to weaning when the milk replacer contained two-thirds or more of the FPH. The FPH-fed calves had lower hay intakes than those fed milk only. Treatment differences in post-weaning live-weight gain reflected mainly differences in concentrate intake. There was no significant difference in live-weight gain nor food efficiency for calves fed either undried or dried FPH in any period to 84 days. The number of treatments for scour was similar for the two groups. However, the calves fed dried FPH had a lower dry-matter intake in the post-weaning period.

Determining optimal heat treatment of soybeans by measuring available lysine chemically and biologically with rats to maximize protein utilization by ruminants

Soybeans were heated in a forced air oven at 120 and 130 degrees C for 60 and 180 min, and at 140, 150 and 160 degrees C for 10, 30, 60, 90 and 120 min. Two types of measurements were used to determine optimal heat treatment of soybeans to maximize protein utilization by ruminants. One was to estimate the rate and extent of protein degradation in the rumen using an in vitro ruminal system. The second was to determine the nutritional availability of lysine. Methods used to determine available lysine were an indirect fluorodinitro-benzene chemical method and a rat growth assay. The product of undegraded intake protein and available lysine content was used to estimate the amount of lysine that would escape ruminal degradation and be available for intestinal absorption. As heat input increased, ruminal undegraded intake protein increased, and protein degradation rates and total and available lysine decreased. As temperature increased, the time required to maximize post-ruminal available lysine decreased. The optimal heat treatment for soybeans heated in a forced air oven was: 140 degrees C for 120 min or greater, 150 degrees C for 60 min or 160 degrees C for 30 min. A loss of 15-22% of chemically determined available lysine was necessary to achieve the heat treatment that resulted in maximal post-ruminal available lysine.

Pigeon (Columba L.) meat iron solubility and availability for absorption in rats

1. The distribution of iron in 59Fe-labelled pigeon (Columba L.) leg and breast muscle and liver were determined by gel filtration. While the insoluble Fe was between 14 and 25% of the total Fe from the tissues, the haem-Fe represented 79.1% (breast) to 45% (liver) of the total Fe and ferritin was between 5.5% (breast) and 26.5% (liver) of the total Fe. 2. The tissue haem-Fe concentration was found to be lower than that determined by gel filtration using the method of Schricker et al. (1982) for non-haem-Fe and obtaining haem-Fe by difference. 3. A simulated in vitro digestion procedure showed significantly (P less than 0.01) reduced 59Fe solubility from 59Fe-labelled pigeon meat after cooking at 90 degrees for 30 min. 4. 59Fe absorption from whole pigeon meat and soluble extract was significantly reduced by cooking when given to Fe-replete rats. Cooking liver, however, slightly improved 59Fe absorption in Fe-replete rats. 5. 59Fe absorption from the separated pigeon-meat fractions (haemoproteins, ferritin and haemosiderin) was variable but considerably lower than that from whole meat. 6. The relative distribution of Fe compounds in meat, the processing conditions they are subjected to and the protein content and composition may all influence the absorption of meat-Fe to some degree.

Texturized proteins: fabrication, flavoring, and nutrition

This paper provides a comprehensive review of the current methods used for the texurization of proteins, with emphasis on soy proteins. The sensory characteristics, i.e., flavor, texture, and color are discussed, particularly in relation to the problems of simulating meat flavored products. The nutritional qualities of texturized products are reviewed, and current regulations concerning their use in foods are cited.

The physical aspects with respect to water and non-enzymatic browning

Non-enzymatic browning is one of the major probles that occurs during the processing and storage of dehydrated and semi-moist foods. One type of browning is the Maillard reaction between reducing sugars and proteins or free amines. This leads to a darkening of color, protein insolubility with subsequent possible nutrition loss and a bitter off-flavor. The reaction has been extensively researched since the early 1940's. From a storage standpoint, browning rate increases as water activity (aw) increases up to a maximum where reactant dilution causes a subsequent decrease in rate. Use of liquid humectants in high moisture foods increase phase volume and viscosity, thereby lowering the aw of the rate maximum. These humectants thus act as inhibitors at high aw. Sorbitol also decreases the rate by a viscosity effect. Kinetic studies at normal storage conditions show browning to occur by a zero order reaction although the sugar and amine initial reaction occurs by first order. Studies with Tetrahymena show that the initial Schiff's base and reaction products may be partially biologically available although chemical assays show up to 50% loss of protein value. For dehydrated foods the zero order kinetics can be used to predict shelf life under a variable time-temperature-humidity condition.