F. Liu, A. Osman* and H.M. Ghazali

Faculty of Food Science and Biotechnology, Universiti Putra Malaysia UPM 43400 Serdang, Selangor Darul Ehsan

Received 15 August 2000 / Accepted 10 November 2000

Abstract.
Peeling is one of the most important preparatory steps in the processing of some fruits and vegetables. Pectic enzymes have been found to be able to selectively alter the albedo structure of citrus fruits and thus aid in the removal of citrus peel and the adhering albedo. Mandarin orange (Citrus suhuiensis) is a local citrus fruit that has the potential to be enzymatically peeled as it has a thin layer of peel and albedo. The objective of this study is to determinc the ease of peeling of C. suhuiensis with the aid of pectic enzymes. Five different concentrations of enzyme ranging from 0 to 0.5% v/w was applied and five different vacuum infusion durations ranging from 5 to 15 minutes were used. The oranges were first scored with eight radial lines from stem end to blossom end followed by the immersion of the oranges in the enzyme solution at 700 mm Hg, pH 4.5 and at ambient temperature (27±1oC; 60 80% RH). The time taken for complete peel removal was observed for each different enzyme concentration and for each different vacuum duration tested. There was a significant (P<0.05) difference in time taken to peel the oranges at different enzyme concentrations and at different vacuum duration. Peelzym® IV at 0.4%v/w and vacuum duration of 13 min were found to be optimal for peeling producing fruits that were relatively free of adhering albedo arid firm.

Keywords: Peeling, enzyme aided infusion, pectic enzymes, vacuum infusion, minimal processing, Mandarin Orange

S. Abd Aziz* and L.O. Gaik Ai

Biotechnology Department, Faculty of Food Science and Biotechnology, University Putra Malaysia, 43400 Serdang, Selangor, Malaysia

Received 13 July 2000 / Accepted 15 September 2000

Abstract.
Studies on the enzymatic hydrolysis of the rice protein (Oryza sativa Basmati) by two commercial enzymes, Flavourzyme and Alcalase, have been investigated. To understand the process variable involved in producing hydrolytic products from rice protein, the estimation of degree of hydrolysis was determined by measurement of free amino groups and by proton release method. These studies have shown that the degree of hydrolysis of rice protein was controlled by temperature, substrate concentrations, the type of enzyme used and enzyme concentrations. The pKa for Flavourzyme and Alcalase were 5.43 and 6.07, respectively. The results show that the suitable hydrolysis condition for Flavourzyme were 4% substrate concentration, 150 mg/mI enzyme concentration, pH 8.0 and at optimum temperature of 55^oC. While for Alcalase the suitable hydrolysis condition for Alcalase were 4% substrate concentration, 200 mg/ml enzyme concentration, pH 8.0 and at optimum temperature of 60^oC. The enzyme decay determination were also done to each of the enzyme used and it was found that at optimum operating temperature, the half life for Flavourzyme and Alcalase were 15.42 min and 11.25 min, respectively.

Keywords: Enzymatic hydrolysis, pH stat method, protein hydrolysate, rice protein

G. Subramanian¹, S. Puthucheary¹, R. Yassin², T Pang³ and K. L. Thong⁴

¹Dept. of Medical Microbiology, Faculty of Medicine, 4Inst. ofPostgraduate Studies and Research, Faculty of Science,
University of Malaya, 2Inst. of Medical Research, Kuala Lumpur, Malaysia, 3WHO, Geneva.

Received 15 August 2000 / Accepted 15 November 2000

Abstract.
The complete 16S rRNA gene (rDNA) sequences of 15 strains of Salmonella species have been analyzed using direct sequencing of PCR amplicons generated using universal primers. The percentage similarity between the Salmonella spp. studied was very high (96.4 to 99.2%) indicating a high degree of sequence conservation within this gene. Among the serovars studied, S. bovismorbificans was found to be the most dissimilar compared to the others. The base substitutions detected occurred throughout the gene with two apparent 'hot spots' or signature regions, one of which corresponded to the V6 hypervariable region of the 16SrRNA gene. In addition, a 9-base pair insertion and a 5 base pair deletion were discovered in S. waycross and S. matopeni, respectively. We have also detected the presence of putative Salmonella specific sequences within the 16S rRNA gene which can be used in the design of a species specific probe. The Salmonella serovars studied appeared to belong to a single species that can be divided into four subclusters. Interestingly, the three human adapted serovars associated with human enteric fever, that is, S. typhi, S. paratyphi A and S. paratyphi C, were grouped in the same cluster.

Keywords: 16S rRNA sequencing, Salmonella spp., genomic analysis

C.C. Sieo¹, N. Abdullah^2*, S. Jalaludin³ and YW. Ho¹

¹Institute of Bioscience, ²Department of Biochemistry and Microbiology, ³Department of Animal Science,
Universiti Putra Malaysia, 43400 UPM Serdang, Selangor Darul Ehsan, Malaysia.

Received 26 May 2000 / Accepted 14 October 2000

Abstract.
A study was carried out to detect the cellulose binding proteins (CBPs) of Ruminococcus albus D3, isolated from the rumen of a Sika deer. Buffer A supplemented with either 1% (w/v) carboxymethylcellulose (CMC or 10% (w/v) cellobiose or 5% (w/v) sodium dodecyl sulphate (SDS) was used to elute CBPs from avicel incubated with cell lysate of R. albus. Buffer A supplemented with CMC eluted two major proteins with molecular weights of 120 kDa and 100 kDa, and a few minor proteins ranging from 35 kDa to 60 kDa. Buffer A supplemented with cellobiose or SDS eluted proteins with approximate weights of 240, 120 and 100 kDa. Among the three CBPs, die 240 kDa CBP showed xylanase activity

Keywords: cellulose binding proteins, rumen bacteria, Ruminococcus albus