Pork products have digestible indispensable amino acid scores that are greater than 100, but processing does not always increase amino acid scores

226

ork is the most widely consumed animal meat in the world accounting for approximately 40% of the total global meat intake. Pork almost always undergoes some degree of processing prior to consumption. Consequently, thermal processing induces modification to the 3-dimentional structure of proteins, which may lead to increased digestibility of amino acids (AA).

Protein quality is evaluated in human foods by the digestible indispensable amino acid score (DIAAS) methodology, which can be described as the digestibility of individual dietary indispensable AA (IAA) compared with the same IAA in 1 of the 3 reference protein patterns established by the Food and Agriculture Organization of the United Nations (FAO). Values for DIAAS of bovine meat cooked by various techniques have been determined, yet to our knowledge, there are no reported DIAAS values for pork products and the IAA digestibility of pork after processing has not been reported.

Therefore, the objective for the present work was to determine DIAAS values for pork products, and to test the hypothesis that processing may increase protein quality.

Materials and methods

Nine pork products that underwent different processing techniques were used in the current study. Products included, pork belly processed by 3 different methods: raw belly, smoked bacon, and smoked-cooked bacon, 3 sources of fully-cooked ham: non-cured, alternatively cured with celery salt, and conventionally cured with Prague powder, and pork loin heated to 3 different temperatures: 63oC, 68oC, or 72oC.

Ten gilts (initial BW: 26.63 ± 1.62 kg) were surgically fitted with a T-cannula in the distal ileum and randomly allotted to a 10 × 10 Latin square design with 10 diets and ten 7-d periods with ileal digesta collection for 9 h on d 6 and 7. Pigs were housed in individual pens (2 by 3 m) equipped with smooth plastic siding, partially slatted floors, a feeder, and a nipple drinker. A single pork product was included in 9 of the diets as the only crude protein (CP) and AA containing ingredient, and a N-free diet was also formulated to determine basal endogenous losses of CP and AA. At the conclusion of the experiment, all pork products, the N-free diet, and all ileal digesta samples were analyzed for AA and values for standardized ileal digestibility (SID) were calculated. The DIAAS values were then calculated using the determined concentration of digestible IAA in each pork product and 2 reference protein patterns established by the FAO; 1) children 6 mo to 3 yr and 2) children > 3 yr, adolescents, and adults.

Results

All pork products had a DIAAS value greater than 100 (Table 1), regardless of the reference protein pattern and processing method. When compared with the 2 human AA requirement patterns, Val was the limiting AA in all pork products, except for smoked-cooked bacon, which was limiting in Trp for children 6 mo to 3 yr. For both reference patterns, among the pork bellies, smoked-cooked bacon had the greatest (P < 0.05) DIAAS value with no difference observed between raw belly and smoked bacon. The SID of IAA in smoked-cooked bacon was lower (P < 0.05) than for raw belly (Table 2), but no differences were observed between the other bellies. Among the pork hams, alternatively cured ham had the greatest (P < 0.05) value for DIAAS with no difference observed between conventionally cured and non-cured ham. Alternatively cured and conventionally cured ham had greater (P < 0.05) SID of IAA compared with non-cured ham. The loin heated to 63oC had a greater (P < 0.05) DIAAS value than the loins heated to 68oC and 72oC, with no differences observed between the DIAAS of 68oC and 72oC loin, as well as no differences were observed in the SID of IAA among all loins.

Key points

  • Pork products are excellent quality proteins with DIAAS values greater than 100.
  • DIAAS values greater than 100 indicate the potential of these pork products to complement low quality proteins producing a diet adequate in all IAA.
  • Various forms of processing did not negatively affect DIAAS, and curing and moderate heating of pork products may increase protein quality.

Table 1. Standardized ileal digestibility (SID) of amino acid (AA) in ingredients1,2

Item

Raw belly

Bacon

Ham

Loin

Pooled SEM

P-value

Smoked

Smoked-cooked

Non-cured

Alt. cured3

Conv. cured4

63 oC

68 oC

72 oC

Indispensable AA, %
Arg

100.3a

98.6bc

99.4ab

98.0c

99.2b

99.6ab

99.0bc

99.5ab

99.3ab

0.44

0.008

His

98.5a

96.7b

94.8c

93.4d

95.0c

95.8bc

95.6bc

96.2bc

95.9bc

0.61

<0.001

Ile

97.8a

96.6ab

96.1b

93.9c

96.4ab

97.1ab

95.9b

95.7b

96.0b

0.63

0.001

Leu

98.0a

96.8ab

96.5b

94.8c

96.9ab

97.4ab

96.5b

96.3b

96.5ab

0.61

0.011

Lys

98.5a

97.2ab

96.7bc

95.7c

97.1b

97.8ab

97.4ab

97.3ab

97.4ab

0.52

0.009

Met

98.0a

97.4ab

97.0b

95.8c

97.3ab

97.7ab

97.3ab

97.1ab

97.1ab

0.39

0.007

Phe

97.6a

95.9ab

95.8b

93.9c

96.1ab

96.8ab

95.7b

95.8b

95.7b

0.71

0.013

Thr

97.8a

95.8ab

95.8ab

92.8c

96.3ab

96.7ab

95.5b

95.6ab

95.5ab

0.91

0.010

Trp

99.0a

97.2ab

95.7bc

92.2d

94.0cd

94.9c

94.5c

95.4bc

95.1c

0.92

<0.001

Val

97.0a

95.4ab

95.4ab

92.6c

95.4ab

96.1ab

94.8b

94.8b

94.9b

0.79

0.005

Mean

98.3a

96.8b

96.5b

94.7c

96.7b

97.3ab

96.5b

96.6b

96.6b

0.61

0.005

Dispensable AA, %
Ala

97.6a

95.7bc

96.4ab

94.6c

96.9ab

97.7a

96.5ab

96.4abc

96.6ab

0.70

0.029

Asp

97.3a

95.6ab

95.1bc

87.2e

94.5bcd

95.3abc

93.7bcd

93.3cd

93.0d

0.91

<0.001

Cys

92.6a

88.7ab

88.4ab

77.1c

88.5ab

89.1ab

85.3b

84.8b

85.9b

2.05

<0.001

Glu

97.8a

96.3ab

96.5ab

93.5c

96.2ab

97.3ab

95.5b

96.1ab

96.6ab

0.80

0.007

Gly

102.9a

96.9cd

99.0bc

95.1d

103.2a

102.1ab

100.8ab

99.8abc

99.8abc

1.58

<0.001

Ser

99.1a

96.9ab

96.9ab

93.2c

96.7b

97.5ab

96.1b

96.4b

96.5b

0.91

0.002

Tyr

98.0a

96.8ab

95.5bc

94.8c

95.9bc

96.7ab

96.2bc

96.7ab

96.5ab

0.64

0.015

Mean

102.2a

99.7b

99.2b

96.0c

100.2ab

101.1ab

99.1b

99.8b

99.9b

0.87

<0.001

Total AA, %

100.2a

98.2b

97.9b

95.3c

98.4b

99.1ab

97.8b

98.1b

98.2b

0.73

<0.001

a-eMeans within a row lacking a common superscript letter differ (P < 0.05).

1Data are least squares means of 10 observations per treatment except for smoked bacon, conventionally cured, alternatively cured, and non-cured ham, and 63 oC loin that have 9 observations per treatment and for raw belly, 68 oC, and 72 oC loin that have 8 observations per treatment.

2Standardized ileal digestibility values were calculated by correcting values for apparent ileal digestibility for the basal ileal endogenous losses. Endogenous losses (g/kg of dry matter intake) AA were as follows: crude protein, 14.99; Arg, 0.58; His, 0.22; Ile, 0.39; Leu, 0.66; Lys, 0.58; Met, 0.09; Phe, 0.42; Thr, 0.72; Trp, 0.16; Val, 0.48; Ala, 0.58; Asp, 0.94; Cys, 0.26; Glu, 1.05; Gly, 1.63; Pro, 3.67; Ser, 0.63; Tyr, 0.34.

3Alt. cured = alternatively cured ham.

4Conv. cured = conventionally cured ham.

 

Table 2. Digestible indispensable amino acid scores (DIAAS) of the 9 pork products1

 

Ingredient

DIAAS, %

Children 6 mo to 3 yr2 Older children, adolescence, and adults3
Raw belly

111e (Val)

119e (Val)

Smoked bacon

109e (Val)

117e (Val)

Smoked-cooked bacon

126b (Trp)

142a (Va;)

Uncured ham

115d (Val)

124d (Val)

Alternatively cured ham

123c (Val)

133c (Val)

Conventionally cured ham

117d (Val)

126d (Val)

63oC loin

129a (Val)

139b (Val)

68oC loin

109e (Val)

118e (Val)

72oC loin

109e (Val)

117e (Val)

   Pooled SEM

0.99

1.08

   P-value

<0.001

<0.001

a-fMeans within a row lacking a common superscript letter differ (P < 0.05).

1First-limiting AA is in parentheses.

2DIAAS were calculated using the recommended AA scoring pattern for a child (6 mo to 3 yr). The indispensable AA reference patterns are expressed as mg AA/g protein: His, 20; Ile, 32; Leu, 66; Lys, 57; sulfur AA, 27; aromatic AA, 52; Thr, 31; Trp, 8.5; Val, 40 (FAO, 2013).

3DIAAS were calculated using the recommended AA scoring pattern for older child, adolescent, and adult. The indispensable AA reference patterns are expressed as mg AA/g protein: His, 16; Ile, 30; Leu, 61; Lys, 48; sulfur AA, 23; aromatic AA, 41; Thr, 25; Trp, 6.6; Val, 40 (FAO, 2013).

LEAVE A REPLY

Please enter your comment!
Please enter your name here