猪的好口感(第一章)；甜味

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猪的好口感(第一章)；甜味

2011年4月19日

作者: Eugeni Roura 译者：刘彩红

动物食物的研究由化学感受器编码引发，它能够感觉可用原料的营养价值。食物通过口腔进入胃肠道（GIT），在吞咽前食物在口腔中经过好几个化学和生理变化反复咀嚼、感受。并饥饿时，化学感受器编码主要存在于口腔中（主要是嗅觉和味觉），感受食物营养，并触发或阻止进一步采食。凭借胃肠道-丘脑轴的外围传感器决定头期采食量，并且对于食物的营养和大概用量有一个直接的评价（暂时的）。

   简单的碳水化合物，例如糖，似乎可以刺激猪甜味感官，增强猪的自由采食。猪日粮中甜味剂的使用是一种普遍实用技术，尤其是对于幼小的动物。在其他的甜味剂中，非碳水化合物高强度甜味剂（HIS）例如糖精（SAC）、索马甜（THA）、蛇菊苷和新橙皮苷（NHDC）被广泛地使用。Kennedy 和 Baldwin (1972)研究了蔗糖、葡萄糖、糖精的喜好参数，并建立阈值，蔗糖的参数为0.005-0.01M，葡萄糖为0.01-0.03M。两种物质猪都表现出一致的偏爱（超过90%）。相反，SAC的结果不同，其喜好参数没有改善蔗糖，阈值为0.0005=0.1M.此外，SAC的喜好价值没有超过90%，浓度超过0.1M时被拒食。
      Danilova等（1999）进行了电生理学研究，报告称猪舌头对于碳水化合物甜味剂有高度神经元应答，比如存在于单糖或低聚糖之中的果糖，蔗糖或乳糖。在偏好特征测定中，蔗糖在多有碳水化合物测试总表现出最高强度的喜欢，它们的反应与人的糖感觉测试非常相似（Glasser等，2000年）。另一方面，猪对于与人类等同剂量的的HIS没有应答，例如NHDC，THA，或者SAC（表1）。HIS广泛使用在猪的饲料中，如SAC和NHDC和/或THA处理组合也没有表现出更好的应答。
表1  相对于蔗糖（在1摩尔质量基础上），甜味剂对猪和人的效应（Glasser等，2000）

		相对于蔗糖的作用
		人类	猪(1)
碳水化合物	蔗糖	1.00	1.00
	果糖	0.50	0.50
	乳糖	0.33	0.15
	葡萄糖	0.25	0.13
非碳水化合物	阿斯巴甜	155	< 1.00(2)
	甜蜜素	17.6	< 0.15(2)
	新橙皮苷（二氢查耳酮）	3.6	< 151(2)
	索马甜	2	< 1.622(2)
	糖精	215	3.34

（1）甜味剂对猪的作用测定建立在偏好双重选择偏好测试的基础上

（2）等同于没有应答反应的最低剂量测试。精确的作用未被测定。
然而，近年来，甜味尝试领域已经尝试突然的转变，这是由于味觉受体（TR）不仅存在于口腔味觉簇（味蕾）中，而且也存在在没有味觉的组织中尤其是在胃肠道黏膜中。据称，在胃肠道黏膜中的味觉受体应答与采食后的活动有关，如识别消化管腔内的营养成分（如葡萄糖）和消化吸收的促进作用(Dyer等. 2005, Mace等， 2009)。

图1

图1 钠-葡萄糖共转运载体（红色）和R1R2（绿色）沿着猪小肠隐窝- 绒毛轴表达

这张图片已经被《英国营养学期刊》和相应的原始作者S. Shirazi-Beechey同意复制。原文参考：Moran AW, Al-Rammahi MA, Arora DK, Batchelor DJ, Coulter EA, Daly K, Ionescu C, Bravo D y Shirazi-Beechey. 断奶仔猪采食人工甜味剂后，钠-葡萄糖共转运载体（SGL1）表达加强。2010年9月营养期刊，剑桥大学出版。

图2

图2，猪采食人工甜味剂后，钠-葡萄糖共转运载体在应答中进入猪小肠刷状缘膜囊的初始速率。甜味剂有，瑞甜甜（43S），糖精（43Sa），新橙皮苷二氢查耳酮（43N，NHDC）或糖精NHDC（43SaN）。平均值显著差异使用*P < 0.05, **P < 0.01, ***P < 0.001.标注。这张表被被《英国营养学期刊》和相应的原始作者S. Shirazi-Beechey同意复制。原文参考Moran等. 英国营养期刊 (2010), 104: 637-646, 剑桥大学出版。

这些相关研究建立在人用HIS似乎是不能积极增肌仔猪的采食量的观点上，然而，它们可能会起到一个推动幼畜碳水化合物消化/吸收的重要作用。找到真正的助食/味道强化剂的任务仍然在进行，但是SAC,THA和/或NHDC的使用依据它们的后肠效果来判定似乎是无可非议的。

英文原文

The good taste of pigs (part I): let it be sweet

19-Apr-2011

Eugeni Roura

The search of animals for food is driven by a chemosensory code that senses the nutritional value of the available sources. Foods enter the gastrointestinal tract (GIT) through the oral cavity where its components are scrutinized and discriminated according to several chemical and physical parameters before swallowing. In hunger the chemosensory systems located in the oronasal cavity (mainly smell and taste) sense dietary nutrients and trigger or discourage further consumption. Via the GIT-hypothalamus axis peripheral sensing determines the cephalic phase of food consumption and has a direct and immediate (short term) impact on meal initiation and presumably meal size.
Simple carbohydrates, like sugars, seem to stimulate sweet taste in pigs enhancing voluntary intake. The use of sweeteners in pig diets is a common practice particularly in young animals. Among other sweeteners, non-carbohydrate high intensity sweeteners (HIS) such as saccharin (SAC), thaumatin (THA), stevioside and neohespiridine (NHDC) are widely used. Kennedy and Baldwin (1972) studied preferences to sucrose, glucose and SAC establishing thresholds that ranged from 0.005 to 0.01M for sucrose and from 0.01 to 0.03M for glucose. For both substances pigs showed consistent preferences (higher than 90%). In contrast, results for SAC were more variable and the threshold for preference did not improve sucrose and was established to be between 0.005 and 0.1M. Furthermore, preference values to SAC solutions were never higher than 90% and concentrations above 0.1 M resulted in rejection.
Danilova et al. (1999) performed electrophysiological studies in pig tongue reporting high neuronal responses to carbohydrate sweeteners such as fructose, sucrose or lactose among other mono and oligosaccharides. In preference trials sucrose showed the highest intensity of all the carbohydrates tested and their responses were very similar to sugar sensory tests in humans (Glasser et al., 2000). On the other hand pigs did not respond to human equivalent doses of HIS such as NHDC, THA, or SAC (Table 1) and the HIS combinations widely used in pig feeding such as SAC with NHDC and/or THA did not give any better response either.

Table 1. Sweetener potencies relative to sucrose (on a molar basis) in humans and pigs (adapted from Glasser et al., 2000).

		Potency relative to sucrose
		Humans	Pigs(1)
Carbohydrates	Sucrose	1,00	1,00
	D-fructose	0,50	0,50
	Lactose	0,33	0,15
	D/l-glucose	0,25	0,13
Non-Carbohydrates	Aspartame	155	< 1,00(2)
	Cyclamate (Na+ salt)	17,6	< 0,15(2)
	Neohesperidin (dihydrocalcone)	3.6	< 151(2)
	Thaumatin	2	< 1.622(2)
	Saccharin	215	3,34

(1)Sweetener potencies in pigs were measured based on double choice preference tests.
(2) Equivalent to the lowest dose tested that gave no response. The exact potency was not determined.

However, in recent years the field of sweet taste has experienced a sudden twist due to the presence of taste receptors (TR) not only in clusters in the oral cavity (taste buds) but also in non-taste tissues particularly in the mucosa of the GIT. It is believed that the TR expression in the GIT mucosa is related to post-ingestive events such as the recognition of nutrients in the lumen (i.e. glucose) and the facilitation of digestion and absorption (Dyer et al. 2005, Mace et al. 2009). Furthermore, TR in enteroendocrine cells may participate in the complex events leading to control of feed intake. For example, dietary carbohydrates and some HIS may increase glucose absorption by stimulating the T1R2 receptor in the gut mucosa which, in turn, triggers active glucose transport through the SGLT1. Porcine sweet TRs have been involved in up-regulating SGLT1 and glucose uptake after stimulation with sucrose, SAC or NHDC in piglet intestinal mucosa (Figures 1 and 2 –Moran et al. 2010-). If these findings would be confirmed we could speculate in HIS to be involved in improving glucose uptake but also to initiate an orexigenic response through GLP1, thus potentially enhancing feed intake in piglets through post-ingestive events.

Fig 1. Expression of Na++/glucose co-transporter 1 (SGLT1) in red and T1R2 in green along the crypt–villus axis of swine small intestine.

This Figure has been reproduced with permission of the British Journal of Nutrition and corresponding author of the original publication Dr. S. Shirazi-Beechey. Original reference: Moran AW, Al-Rammahi MA, Arora DK, Batchelor DJ, Coulter EA, Daly K, Ionescu C, Bravo D y Shirazi-Beechey. Expression of Na+/glucose co-transporter 1 (SGLT1) is enhanced by supplementation of the diet of weaning piglets with artificial sweeteners. 2010 Sep. Br J Nutr. Cambridge University Press.

Fig 2. Initial rates of Na+-dependent d-glucose uptake into brush-border membrane vesicles measured in swine mid-small intestine in response to feed supplementation with the artificial sweeteners, Sucram (43S), saccharin (43Sa), Neohesperidin dihydrochalcone (NHDC, 43N) or saccharin and NHDC (43SaN). Mean values were significantly different: *P < 0.05, **P < 0.01, ***P < 0.001. This Figure has been reproduced with permission of the British Journal of Nutrition and corresponding author of the original publication Dr. S. Shirazi-Beechey. Original reference: Moran et al. British Journal of Nutrition (2010), 104: 637-646, Cambridge University Press.

The relevance of these findings stands in that human HIS do not seem to be effective in increasing feed intake in piglets, however, they may play an important role in improving the efficiency of carbohydrate digestion/absorption in young animals. The task of finding true appetite/taste enhancers remains then unfinished but the use of SAC, THA and/or NHDC seems justified in the light of their post-ingestion effects.

英文来源：pig333.com