F. H. Wolfe

The Effect of Ultrafiltration on Physicochemical Properties of Retentate

Abstract Commercial HTST pasteurized skim milk was concentrated from volumetric concentration factor (VCF) 1:1 to the maximum VCF of 5:1 in a laboratory DDS ultrafiltration unit fitted with twenty 0.018 m 2 membranes with molecular weight cut-off 25,000 daltons. The composition, buffer capacity (dB/dpH) and contribution of retentate components in the buffer capacity were determined. The compositions of retentates of different concentration factors showed almost complete retention of milk fat, casein and whey proteins. The total amount of lactose and minerals removed from skim milk during ultrafiltration from VCF 1:1 to 5:1 were 84.9 and 49.9%, respectively. The contribution of casein, whey proteins and milk salts to the total buffer system intensity of skim milk and retentate (VCF 5:1) were 36.0 vs 53.8%, 5.4 vs 9.7% and 58.6 vs 36.5%, respectively.

Studies of extra low voltage electrical stimulation of mature beef carcasses

The quality characteristics of biceps femoris (BF) and semimembranosus (SM) roasts obtained from mature cow carcasses treated with a commercial extra low voltage (30 V) electrical stimulation (LVES) system were determined. LVES was applied for either 2 (ESII) or 4 min (ESIII). Evaluations were conducted on meat obtained from control sides (no ES) aged for either 48 h (Ia) or 7 days (Ib) and from ES sides aged 48 h. ES caused a reduction (P<0·001) in pH values at 2 and 6 h post mortem. At 24 h, the pH of muscles from all carcasses was about 5·5. ES duration did not influence muscle pH. Rib-eye muscle colour for ESII and ESIII carcasses was lighter and brighter (P<0·05) than that of control carcasses. Generally stimulated BF roasts had greater cooking losses than control Group Ib roasts; SM roasts from ES carcasses had lower losses than comparable to Group Ib roasts. ES duration had no effect on per cent cooking losses. Trained panelists generally detected few significant effects in BF roasts due to ES. Warner-Bratzler data indicated that ESII and ESIII BF roasts were similar and significantly more tender than comparable control Group Ib samples: OTMS data indicated that all BF roasts were similar in tenderness. However, SM roasts from ES carcasses were judged more soft (Groups II and III) and tender (ESII) than comparable control roasts. Instrumental measurements of tenderness for SM roasts tended to support the taste panel results. Generally, duration of LVES had no effect on the eating quality of either BF or SM roasts. Since LVES effects on the palatability of SM roasts were evident but the effects of stimulation of BF roasts were few, further studies of this LVES system are needed before its use can be recommended. Generally, increasing post-mortem ageing time for mature control carcasses did not influence either BF or SM roast quality.

Studies on the Degradation of Ascorbic Acid by Saskatoon Berry Juice

Abstract Ascorbic Acid (Vitamin C) has been shown to be absent although dehydroascorbic acid has been found in several varieties of Saskatoon berries currently being cultivated at the Canada Department of Agriculture Research Station at Beaverlodge, Alberta. Synthetic L-ascorbic acid is rapidly degraded after addition to expressed juice of the berries. Evidence of an ascorbic acid oxidizing system has been revealed, and the effects of pigmentation and approaching maturity on the enzyme system have been examined. The effects of various pigments, polyphenols and copper ions on the oxidation have also been studied, and the implications of these results are discussed.

Gas Chromatographic Analysis of Protein Amino Acid N-Heptafluorobutyryl-Isopropyl Esters

Abstract Standard amino acid mixtures and protein hydrolysates were derivatized to the corresponding N-heptafluorobutyryl-isopropyl esters and quantitated by gas-liquid chromatography. Selected temperatures and times were 80°C and 120 minutes for esterification and 110°C and 10 minutes for the acylation. Quantitative data obtained from chromatograms compared favorably with ion-exchange column chromatography results. Total analysis time was in the order of 11–14 minutes for the GLC method.

Manufacturing processes influence the proteolytic action of rennin on casein in several dairy products

Abstract Research was undertaken to estimate the extent of change in milk proteins brought about by industrial processes that are utilized in the manufacture of skim milk powder, evaporated milk, sodium caseinate and sodium coprecipitate. Potentiometric titration was used to determine the differences in the accessibility of functional groups. The kinetics of release of peptides soluble in 2% (w/v) TCA and glycopeptides soluble in 12% (w/v) TCA from casein substrates by rennin were determined. The casein substrates showed a diversified susceptibility to the action of rennin. The velocity of total peptides release at pH 5·6 decreased (p ≤ 0·05) in the following order: reconstituted condensed milk > sodium coprecipitate > sodium caseinate > reconstituted skim milk powder. Km values for total peptide release were higher (lower affinity) (p ≤ 0·05) in sodium coprecipitate and sodium caseinate than in evaporated milk and skim milk powder. The velocity of glycopeptides release differed (p ≤ 0·05) for all substrates at pH 6·6. Km values for the release of glycopeptides ranged from 4·8 × 10−5 to 5·4 × 10−5 m and were lowest (p ≤ 0·05) in skim milk powder at pH 6·6 and 5·6 and evaporated milk at pH 5·6. It was concluded that the susceptibility of the casein to proteolysis in milk products was influenced by processing.