The effect of muscle type and freezing on the evolution of physico-chemical properties during processing of South African biltong and its final textural properties
- Authors: Ngwendu, Nwabisa
- Date: 2020
- Subjects: Biltong Meat -- Quality -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/12128 , vital:39154
- Description: The study investigated the effect of muscle type and freezing on evaluation of mass transfer during processing physico-chemical of South African biltong and its textural properties. In the first experimental phase of this study, mass transfers, physico-chemical and textural properties (hardness, cohesiveness, springiness, and chewiness) of commercially produced biltong from biceps femoris (BF) and semitendinosus (ST) (n=9) were measured. Biltong was dried at 30oC and 40% relative humidity until it had lost 50% of its initial weight. The initial moisture content, water activity (Aw) of BF muscles (74.3% and 0.992) were significantly lower compared those of ST muscles (75.4% and 0.994%). The fat content of BF (2.3%) muscles was higher (P<0.05) than in ST muscles (1.7%). The salt, weight and water gain for the BF muscle were 2.3%, -2.6% and -7.0% respectively and were significantly higher than those of ST muscles which were 2.1, -0.4 and -4.0, respectively. After drying, the moisture content, Aw, and pH were lower in BF (42.2, 0.886 and 5.29) than those of ST muscles (45.1, 0.911 and 5.42). The salt content was higher (P<0.05) in BF muscle than in ST. Among textural properties, hardness was significantly higher in biltong from the BF (233.0N), while the springiness was significantly lower compared to the ST muscle (178.2N). Therefore, it was concluded that the use of different muscles results in variation of biltong physicochemical characteristics. The second experiment investigated the effect of freezing and muscle type on mass transfers, lipid oxidation, physico-chemical and textural properties of biltong. In this experiment, the iii ST muscles were replaced with semimembranosus (SM) muscles. A total of 12 beef muscles were used, with six BF and six SM muscles frozen in a blast freezer at -40 oC till they reached -20oC; then they were transferred to -20oC for 14 days. The thawing loss for the BF and ST muscles was 1.3 and 2.4% respectively, but there were no significant (P>0.05) differences. The protein and salt content were significantly higher in frozen-thawed (24.3 and 0.13%) muscles than in fresh muscle (20.2 and 0.08%); whereas the fat content and pH were lower (P<0.05) in frozen-thawed (5.36) compared to fresh muscles (5.51). Between muscles, the moisture, salt content, and pH were higher in BF muscles than in SM muscles (73.2, 0.12% and 5.49). Aw was affected by the interaction between freezing and muscle type, with frozenthawed SM having lower Aw (0.990). During salting, salt, weight and water gain did not show any differences (P<0.05). There were no major significant differences after salting. There were lower TBARS and pH in frozen-thawed (1.5mgMDA/kg and 5.15) muscles than in fresh muscles (3.3mgMDA/kg and 5.19) as well as in SM muscles (1.8mgMDA/kg and 5.16) than in BF muscles (3.0mgMDA/kg and 5.19). The moisture was significantly lower in frozen-thawed SM (68.1%) than in fresh SM, BF and frozen-thawed BF (69.3,70.5 and 71.7%) after salting. On the final product, the interaction between muscle type and freezing affected the moisture content, TBARS, chewiness and the springiness of biltong, with the biltong from fresh SM (39.8%) having significantly lower moisture content compared frozenthawed BF and ST muscles as well fresh BF muscles (42.8% in average). The TBARS were higher in biltong from fresh BF muscles (5.1mgMDA/kg) compared to other muscles. Furthermore, the chewiness and springiness were higher (P<0.05) in biltong produced from SM frozen-thawed muscles (327.7N and 1.5). The WBSF was higher in biltong from the BF muscles (108.8N) than in the biltong from SM (80.1) but it was not affected by the freezing effect (P>0.05). Freezing did not show any major differences in biltong. iv The third experiment was conducted to determine the effect of freezing African buffalo carcasses on weight loss during salting, physico-chemical and textural properties of biltong. Five muscles (ST, SM, BF, LTL, and RF) were randomly selected from 30 carcasses (15 frozen-thawed and 15 fresh), cut along the grain, traditionally salted and dried at 26oC till they lost 45-50% of their initial weight. The salting weight loss was higher in frozen-thawed muscles (-1.45%) than in fresh muscles (-0.89%). The freezing treatment affected the physico-chemical properties of the biltong. The biltong produced from frozen-thawed muscles showed significantly higher protein and ash (47.6 and 7.6%) compared to fresh (43.9 and 7.1); whereas the moisture, fat, pH and Aw were lower (43.7, 2.1, 0.870 and 5.30, respectively) compared to those of biltong from fresh muscles (45.5%, 2.9%, 0.890 and 5.38). The moisture, pH and fat content were further affected by muscle type. The interactive effect was observed in salt content, with RF frozen-thawed showing higher salt content (8.2%) compared to all other muscles. The hardness and WBSF were significantly higher (P<0.05) in biltong frozen-thawed (204.1N and 135.0N) than in fresh muscles (146.2N and 113.1N). Moreover, the chewiness and springiness were affected (P<0.05) by muscle type, with RF muscle having higher springiness 0.89 and chewiness 171.1N than all the other muscles. Therefore, it can be concluded that freezing buffalo carcasses significantly influenced the quality characteristics of biltong. The fourth experiment studied the effect of drying methods on physico-chemical properties of traditional biltong produced from African buffalo muscles. The BF and SM muscles were randomly selected from 15 fresh carcasses, cut into strips, salted and divided into two batches per muscle. The first batch of each muscle type was dried in the ambient-air drier at 22oC average and the second batch in the cabinet drier at 26 oC till 45-50% weight loss. No differences (P>0.05) were observed in salting weight loss between the drying method and muscle type. The protein content was significantly higher in SM (46%) muscles compared to v BF (43%) but there was no effect (P>0.05) caused by the drying method. The interactions between the muscle type and drying method affected the fat content, with biltong from airdried BF muscles having significant lower (2.1%) fat content. There were no significant differences in other physico-chemical properties of biltong, with moisture content, salt, ash content, Aw and pH being 45.0%, 5.13%, 44.8%, 7.3%, 2.7%, 0.885 and 5.61 on average, respectively. Overall, the findings of the study show that freezing does have a significant effect on the final quality of biltong. However, it can be concluded that a significant effect on the physico-chemical properties of biltong depends on the changes of mass transfers during salting and drying.
- Full Text:
- Date Issued: 2020
- Authors: Ngwendu, Nwabisa
- Date: 2020
- Subjects: Biltong Meat -- Quality -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/12128 , vital:39154
- Description: The study investigated the effect of muscle type and freezing on evaluation of mass transfer during processing physico-chemical of South African biltong and its textural properties. In the first experimental phase of this study, mass transfers, physico-chemical and textural properties (hardness, cohesiveness, springiness, and chewiness) of commercially produced biltong from biceps femoris (BF) and semitendinosus (ST) (n=9) were measured. Biltong was dried at 30oC and 40% relative humidity until it had lost 50% of its initial weight. The initial moisture content, water activity (Aw) of BF muscles (74.3% and 0.992) were significantly lower compared those of ST muscles (75.4% and 0.994%). The fat content of BF (2.3%) muscles was higher (P<0.05) than in ST muscles (1.7%). The salt, weight and water gain for the BF muscle were 2.3%, -2.6% and -7.0% respectively and were significantly higher than those of ST muscles which were 2.1, -0.4 and -4.0, respectively. After drying, the moisture content, Aw, and pH were lower in BF (42.2, 0.886 and 5.29) than those of ST muscles (45.1, 0.911 and 5.42). The salt content was higher (P<0.05) in BF muscle than in ST. Among textural properties, hardness was significantly higher in biltong from the BF (233.0N), while the springiness was significantly lower compared to the ST muscle (178.2N). Therefore, it was concluded that the use of different muscles results in variation of biltong physicochemical characteristics. The second experiment investigated the effect of freezing and muscle type on mass transfers, lipid oxidation, physico-chemical and textural properties of biltong. In this experiment, the iii ST muscles were replaced with semimembranosus (SM) muscles. A total of 12 beef muscles were used, with six BF and six SM muscles frozen in a blast freezer at -40 oC till they reached -20oC; then they were transferred to -20oC for 14 days. The thawing loss for the BF and ST muscles was 1.3 and 2.4% respectively, but there were no significant (P>0.05) differences. The protein and salt content were significantly higher in frozen-thawed (24.3 and 0.13%) muscles than in fresh muscle (20.2 and 0.08%); whereas the fat content and pH were lower (P<0.05) in frozen-thawed (5.36) compared to fresh muscles (5.51). Between muscles, the moisture, salt content, and pH were higher in BF muscles than in SM muscles (73.2, 0.12% and 5.49). Aw was affected by the interaction between freezing and muscle type, with frozenthawed SM having lower Aw (0.990). During salting, salt, weight and water gain did not show any differences (P<0.05). There were no major significant differences after salting. There were lower TBARS and pH in frozen-thawed (1.5mgMDA/kg and 5.15) muscles than in fresh muscles (3.3mgMDA/kg and 5.19) as well as in SM muscles (1.8mgMDA/kg and 5.16) than in BF muscles (3.0mgMDA/kg and 5.19). The moisture was significantly lower in frozen-thawed SM (68.1%) than in fresh SM, BF and frozen-thawed BF (69.3,70.5 and 71.7%) after salting. On the final product, the interaction between muscle type and freezing affected the moisture content, TBARS, chewiness and the springiness of biltong, with the biltong from fresh SM (39.8%) having significantly lower moisture content compared frozenthawed BF and ST muscles as well fresh BF muscles (42.8% in average). The TBARS were higher in biltong from fresh BF muscles (5.1mgMDA/kg) compared to other muscles. Furthermore, the chewiness and springiness were higher (P<0.05) in biltong produced from SM frozen-thawed muscles (327.7N and 1.5). The WBSF was higher in biltong from the BF muscles (108.8N) than in the biltong from SM (80.1) but it was not affected by the freezing effect (P>0.05). Freezing did not show any major differences in biltong. iv The third experiment was conducted to determine the effect of freezing African buffalo carcasses on weight loss during salting, physico-chemical and textural properties of biltong. Five muscles (ST, SM, BF, LTL, and RF) were randomly selected from 30 carcasses (15 frozen-thawed and 15 fresh), cut along the grain, traditionally salted and dried at 26oC till they lost 45-50% of their initial weight. The salting weight loss was higher in frozen-thawed muscles (-1.45%) than in fresh muscles (-0.89%). The freezing treatment affected the physico-chemical properties of the biltong. The biltong produced from frozen-thawed muscles showed significantly higher protein and ash (47.6 and 7.6%) compared to fresh (43.9 and 7.1); whereas the moisture, fat, pH and Aw were lower (43.7, 2.1, 0.870 and 5.30, respectively) compared to those of biltong from fresh muscles (45.5%, 2.9%, 0.890 and 5.38). The moisture, pH and fat content were further affected by muscle type. The interactive effect was observed in salt content, with RF frozen-thawed showing higher salt content (8.2%) compared to all other muscles. The hardness and WBSF were significantly higher (P<0.05) in biltong frozen-thawed (204.1N and 135.0N) than in fresh muscles (146.2N and 113.1N). Moreover, the chewiness and springiness were affected (P<0.05) by muscle type, with RF muscle having higher springiness 0.89 and chewiness 171.1N than all the other muscles. Therefore, it can be concluded that freezing buffalo carcasses significantly influenced the quality characteristics of biltong. The fourth experiment studied the effect of drying methods on physico-chemical properties of traditional biltong produced from African buffalo muscles. The BF and SM muscles were randomly selected from 15 fresh carcasses, cut into strips, salted and divided into two batches per muscle. The first batch of each muscle type was dried in the ambient-air drier at 22oC average and the second batch in the cabinet drier at 26 oC till 45-50% weight loss. No differences (P>0.05) were observed in salting weight loss between the drying method and muscle type. The protein content was significantly higher in SM (46%) muscles compared to v BF (43%) but there was no effect (P>0.05) caused by the drying method. The interactions between the muscle type and drying method affected the fat content, with biltong from airdried BF muscles having significant lower (2.1%) fat content. There were no significant differences in other physico-chemical properties of biltong, with moisture content, salt, ash content, Aw and pH being 45.0%, 5.13%, 44.8%, 7.3%, 2.7%, 0.885 and 5.61 on average, respectively. Overall, the findings of the study show that freezing does have a significant effect on the final quality of biltong. However, it can be concluded that a significant effect on the physico-chemical properties of biltong depends on the changes of mass transfers during salting and drying.
- Full Text:
- Date Issued: 2020
Sexual behaviour of adolescent females: a case study of st. Wendolins area, kwaZulu Natal
- Authors: Phelako, Ntokozo
- Date: 2020
- Subjects: Teenagers -- Sexual behavior Youth -- Sexual behavior|
- Language: English
- Type: Thesis , Masters , M (Social Work)
- Identifier: http://hdl.handle.net/10353/11484 , vital:39076
- Description: This study investigated the phenomenon of sexual behaviour of adolescent females, specifically at St. Wendolins in the province of KwaZulu-Natal in South Africa. Adolescence is a critical period for physical, social, and emotional development, and the possibility of adolescents engaging in sexual intercourse is an important social and public health consideration. Sexual intercourse among adolescents is a risk factor for teen pregnancy, clandestine abortions, sexually transmitted infection, school dropouts, and HIV. Adolescents who engage in sexual intercourse may also be exposed to harmful lifestyles, such as use of illicit drugs, alcohol, and cigarette smoking. The South African national HIV public health interventions among adolescents have largely been geared towards sexual abstinence; this emphasis in the prevention interventions may be limited as it may not cater for adolescents with diverse experiences. The study intended to achieve the following specific objectives: to examine the challenges faced by sexual adolescent females; to assess the support services from the social network; and to examine the strategies that are put in place by professionals in supporting teenagers who are sexually active. The study was guided by a qualitative research design in the form of a case study. It also employed in-depth one-on-one interviews, complimented by both focus group discussions and key informants as methods of data collection. The study used nonprobability methodology of sample selection, specifically the purposive sampling technique as well as a snowball . A sample of the study comprised of the nonstudent participants, psychologist, teachers, social workers, Nurses, police officers and other community members Data was analysed qualitatively through content thematic data analysis, which used interpretative approaches and textual presentation. The study established the following: the adolescent stage is a critical time for young girls because of the physical, biological as well as the social changes that they face and need to go through. The factors that face young girls are from all aspects of life; from the home, the community as well as individual factors. The most important factor affecting adolescent females to emerge from the study was social media as a tool that young girls used to learn about sexual behaviour as well as communicating amongst themselves as well as with their sexual partners. 6 The study recommended that the family system needed strengthening. The home is the first place that young girls feel protected, and when the family system is broken down the adolescent females start to look outside and start misbehaving, and end up being sexually active. There should be continuous social work services provided to female adolescents as some are staying alone
- Full Text:
- Date Issued: 2020
- Authors: Phelako, Ntokozo
- Date: 2020
- Subjects: Teenagers -- Sexual behavior Youth -- Sexual behavior|
- Language: English
- Type: Thesis , Masters , M (Social Work)
- Identifier: http://hdl.handle.net/10353/11484 , vital:39076
- Description: This study investigated the phenomenon of sexual behaviour of adolescent females, specifically at St. Wendolins in the province of KwaZulu-Natal in South Africa. Adolescence is a critical period for physical, social, and emotional development, and the possibility of adolescents engaging in sexual intercourse is an important social and public health consideration. Sexual intercourse among adolescents is a risk factor for teen pregnancy, clandestine abortions, sexually transmitted infection, school dropouts, and HIV. Adolescents who engage in sexual intercourse may also be exposed to harmful lifestyles, such as use of illicit drugs, alcohol, and cigarette smoking. The South African national HIV public health interventions among adolescents have largely been geared towards sexual abstinence; this emphasis in the prevention interventions may be limited as it may not cater for adolescents with diverse experiences. The study intended to achieve the following specific objectives: to examine the challenges faced by sexual adolescent females; to assess the support services from the social network; and to examine the strategies that are put in place by professionals in supporting teenagers who are sexually active. The study was guided by a qualitative research design in the form of a case study. It also employed in-depth one-on-one interviews, complimented by both focus group discussions and key informants as methods of data collection. The study used nonprobability methodology of sample selection, specifically the purposive sampling technique as well as a snowball . A sample of the study comprised of the nonstudent participants, psychologist, teachers, social workers, Nurses, police officers and other community members Data was analysed qualitatively through content thematic data analysis, which used interpretative approaches and textual presentation. The study established the following: the adolescent stage is a critical time for young girls because of the physical, biological as well as the social changes that they face and need to go through. The factors that face young girls are from all aspects of life; from the home, the community as well as individual factors. The most important factor affecting adolescent females to emerge from the study was social media as a tool that young girls used to learn about sexual behaviour as well as communicating amongst themselves as well as with their sexual partners. 6 The study recommended that the family system needed strengthening. The home is the first place that young girls feel protected, and when the family system is broken down the adolescent females start to look outside and start misbehaving, and end up being sexually active. There should be continuous social work services provided to female adolescents as some are staying alone
- Full Text:
- Date Issued: 2020
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